Potential of Semi- Natural Management of Deciduous Forests ... … · Preface Adopted at the 1992...

Tropical Forest Research

Potential of Semi-

Natural Management of Deciduous Forests in Thailand

Tropical Forest Research

Potential of Semi-

Natural Management of Deciduous Forests in Thailand

Horst Weyerhäuser Eschborn, 2001

TÖB publication number: TWF-34e

Published by: Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ) GmbH Postfach 5180 D-65726 Eschborn, Germany

Responsible: Begleitprogramm Tropenökologie (TÖB) Michaela Hammer, Elisabeth Mausolf email: [email protected]

Author: Horst Weyerhäuser ICRAF, CMU, P.O. Box 267 Chiang Mai 50202, Thailand email: [email protected]

Layout: Michaela Hammer

ISBN: 3-9801067-3-X

Nominal fee: 5,- €

Produced by: TZ Verlagsgesellschaft mbH, D-64380 Rossdorf

© 2001 All rights reserved

Preface Adopted at the 1992 United Nations Conference on Environment and Development, at which 178 countries were represented, Agenda 21 includes a section devoted to forests. Together with the UNCED Forests Statement, Agenda 21 forms a basis for international cooperation on the management, conservation and sustainable development of all types of forests. The Rio resolutions also serve as the foundation for a process of national-policy modification designed to stimulate environmentally compatible sustainable development in both industrialized and emerging countries.

Ideally, sustainable development builds on three primary guiding principles for all policy-related activities: economic efficiency, social equity and ecological sustainability. With regard to the management of natural resources, this means that their global utilization must not impair future generations' developmental opportunities. With their myriad functions, forests in all climate zones not only provide one of humankind's most vital needs but also help preserve biological diversity around the world. Forest resources and wooded areas must therefore be sustainably managed, preserved and developed. Otherwise, it would neither be possible to ensure the long-term generation of timber, fodder, food, medicine, fuels and other forest-based products, nor sustainably and appropriately to preserve such other important functions of forests as the prevention of erosion, the conservation of biotopes, and the collection and storage of the greenhouse gas CO2.

Implemented by the Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ) GmbH on behalf of the German Federal Ministry for Economic Cooperation and Development (BMZ), the "Tropical Forest Research" project aimed to improve the scientific basis of sustainable forest development and, hence, to help implement the Rio resolutions within the context of development cooperation.

Application-oriented research served to improve our understanding of tropical forest ecosystems and their reciprocity with the economic and social dimensions of human development. The project also served to promote and encourage practice-oriented young German and local researchers as the basis for development and dissemination of ecologically, economically and socially appropriate forestry production systems.

Through a series of publications, the "Tropical Forest Research" project made the studies' results and recommendations for action available in a form that is generally comprehensible both to organizations and institutions active in the field of development cooperation and to a public interested in environmental and development-policy affairs. I. Hoven Dr. C. v. Tuyll Head of Division: Environmental Policy, Protection of Natural Resources, Forestry; CSD, GDF

German Federal Ministry for Economic Cooperation and Development (BMZ)

Head of Division: Rural Development

Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ) GmbH

...When he stood in front of his brothers, to give them the farewell salute, he was

overwhelmed by the disclosure of his own weakness. From that day, the world,

where there remained no longer a place for him, in the extremity of our public perils,

seemed to fade and disappear from his eyes; and, separating himself, without efforts,

from the future which was awanting alike to him and his country, his thoughts rose,

as of themselves, to those regions where, only, the future is never clouded. In going

over some scattered pages, written with a trembling hand, after all was ended, I

found this:

“The life of man has no value except in proportion as he learned to condemn it

by rising above it. To be devoted, is truly to live; to be devoted to the end, is to

live beyond it”

These words are, perhaps, the last he wrote before leaving earth: they contain the

expression of his assurance and mine.

COUNT DE CARNÉ (Notice of the life of the author)

from the book: Travels in Indo-China

and The Chinese Empire

by Louis de Carné London: Chapman and Hall, 193 Piccadilly, 1872

published by White Lotus, 1995 under:

Travels on the Mekong Cambodia, Laos and Yunnan

The political and Trade Report of the Mekong Exploration Commission (June 1866 – June 1868)

To my Parents

Acknowledgements

This study was part of a research project funded by the European Union under the

„Life Science and Technologies for Developing Countries Programme (STD 3)“.

The project entitled „Ecology and Sustainable Semi-Natural Silvicultural

Management of Indigenous Forests in Central Southeast Asia“ (European-Thai-

Forest-Project - ETFP -) was carried out in close co-operation between Thailand,

Italy and Germany, with the Waldbau-Institut of the Albert-Ludwigs-University

Freiburg as the main co-ordinator. I am most grateful for the support of Professor Dr.

J. Huss, Head of the Waldbau Institute, for his guidance and patience.

Additional financial support was provided by the “Tropical Ecology Support

Program “ of the “Deutsche Gesellschaft für Technische Zusammenarbeit” (GTZ).

Without the encouragement of friends and colleagues this research would not have

been possible. Sincere thanks go to my friend and field companion Clemens Fehr.

Many friends and colleagues supported us in Thailand. I can only mention those

who’s efforts contributed significantly to completing our project: Dr. Viroj

Pimmanrojnagool, Samer Limchowong, Chachawan Pitdumkum, Dr. Somsak

Sukwong and Preecha Aranpongpan. Field staff of the Huay Kha Khaeng

headquarters created an environment suitable for field work. Many thanks go to

Khun Surachaat and our field crew, and to the kitchen staff – Pong and Jui. Their

curries helped us to work steadily and efficiently as well as providing the base for

numerous breaks.

My thanks to all those not mentioned who helped in realising this work.

Content

I

Contents

FIGURES .......................................................................................................V

TABLES .....................................................................................................VII

ABBREVIATIONS .................................................................................... VIII

SUMMARY ................................................................................................. IX

1 INTRODUCTION.................................................................................... 1

2 PROBLEM STATEMENT AND RESEARCH OUTLINE ............................ 5

2.1 General problem statement ...............................................................5

2.2 Research needs................................................................................9

2.3 Aim of research ............................................................................. 10

3 REVIEW (UTILISATION OF FOREST RESOURCES IN THE PAST

AND PRESENCE) ................................................................................. 13

3.1 Concessions................................................................................... 14

3.2 Plantations..................................................................................... 17

3.3 Management systems of the past..................................................... 19

3.4 Present management systems.......................................................... 20

3.5 Thai Forestry Master Plan .............................................................. 21

3.6 Previous inventories....................................................................... 22

3.7 Species importance for the regional timber trade ............................. 23

3.8 Past and present influence by local communities ............................. 25

4 CHOICE OF RESEARCH SITE ‘THE HUAY KHA KHAENG

(HKK) WILDLIFE SANCTUARY’ ...................................................... 27

4.1 Location........................................................................................ 28

4.2 History of land use in Huay Kha Khaeng ........................................ 29

4.3 Research site.................................................................................. 30

4.4 The main forest types in the valley.................................................. 31

Potential of Semi-Natural Management of Deciduous Forests in Thailand

II

4.5 Geomorphology............................................................................. 32

4.6 Climate ......................................................................................... 32

5 DATA ASSESSMENT OF STRUCTURE AND SPECIES

COMPOSITION IN MDF AND DDF................................................... 37

5.1 Methods........................................................................................ 37

5.1.1 Interpretation of aerial photographs ..................................................... 37

5.1.2 Research site selection ........................................................................... 39

5.1.3 Placement of temporary plots................................................................ 39

5.2 Floristic assessment and forest type stratification ............................ 42

5.2.1 Statistical methods applied for the analysis......................................... 42

5.2.2 Assessment of the temporary plots....................................................... 44

5.2.3 Resulting dominance-types.................................................................... 48

5.2.4 Verification via correspondence analysis ............................................ 52

6 ASSESSMENT OF THE RESEARCH PLOTS .......................................... 55

6.1 Methods........................................................................................ 56

6.1.1 Establishment of 5 permanent plots ..................................................... 56

6.1.2 Establishment of a 2 ha plot in the Mixed Deciduous Forest............ 57

6.2 Auxiliary data collected in all permanent plots ................................ 58

6.2.1 Fish eye photographs .............................................................................. 58

6.2.2 Increment assessment via borings ........................................................ 61

6.2.3 Soil Survey............................................................................................... 63

6.3 Analysis of the permanent plots...................................................... 64

6.3.1 Species composition and dominance.................................................... 64

6.3.2 Natural regeneration and its dynamics in the permanent plots ......... 66

6.3.3 Distribution of individuals with respect to Social Position............... 68

6.3.4 Diameter distribution.............................................................................. 71

6.3.5 Basal area and increment ....................................................................... 74

6.3.6 Volume ..................................................................................................... 76

6.3.7 Crown characteristics and crown projection area............................... 76

6.4 Selection of potential crop trees...................................................... 79

6.4.1 Methods .................................................................................................... 79

6.4.2 Basal area of the potential crop trees.................................................... 82

6.5 Discussion..................................................................................... 83

Content

III

6.5.1 Permanent plots and their characteristics.............................................83

6.5.2 Selection and establishment of permanent plots .................................84

6.5.3 Structure and species composition of selected permanent plots .......84

6.5.4 Natural regeneration ...............................................................................85

6.5.5 Available light .........................................................................................86

6.5.6 Diameter increment via analysis of bore cores ...................................87

6.5.7 Distribution of individuals across the social position.........................88

6.5.8 Diameter distribution of stands .............................................................89

6.5.9 Basal area and volume of stands ...........................................................90

6.5.10 Crown characteristics and crown projection of stands .......................91

6.5.11 Distribution of potential crop trees in stands .......................................91

7 GROWTH PROGNOSIS FOR THE MIXED DECIDUOUS FOREST

AND SILVICULTURAL CONSIDERATIONS ......................................... 93

7.1 Deriving empirical models for future stand assessments .................. 94

7.2 Development of diameter increment functions................................. 97

7.3 Development of height increment functions .................................. 100

7.4 Restricted prognosis of the growth potential in Mixed Deciduous Forests........................................................................ 101

7.5 Growth and yield of potential crop trees........................................ 103

7.6 Growth and yield of remaining stand (post liberation and refining) ...................................................................................... 105

8 DISCUSSION .....................................................................................109

8.1 Comparability of the Huay Kha Khaeng study site ........................ 109

8.1.1 Forest-type delineation and differentiation........................................109

8.1.2 The characteristics of prevailing forest types ....................................110

8.1.3 Growth prognosis..................................................................................112

8.2 Silvicultural implications of the study........................................... 113

8.3 Necessary preconditions for deciduous forest management in the region ........................................................................................ 117

8.4 Research needs............................................................................ 119

8.4.1 Ecological...............................................................................................119

8.4.2 Methodological ......................................................................................119

8.4.3 Silvicultural ............................................................................................120


IV

8.5 Final conclusion .......................................................................... 120

9 BIBLIOGRAPHY ............................................................................... 123

10 APPENDIX ........................................................................................ 133

10.1 Species list and their respective code (sorted by their CODE) ........ 133

10.2 Growth and Yield of the permanent plots...................................... 139

10.3 Forest types and their distribution................................................. 144

10.3.1 Mixed Deciduous Forests ....................................................................147

10.3.2 Deciduous Forests.................................................................................150

10.3.3 Evergreen Forests .................................................................................154

10.3.4 Tropical Rain Forests ...........................................................................155

10.3.5 Dry Evergreen Forest ...........................................................................156

10.3.6 Hill Evergreen Forest ...........................................................................158

10.3.7 Particular Edaphic Forest Formations ................................................159

10.3.8 Coniferous Forest..................................................................................162

Figures

V

Figures

Figure 1: Import of timber to Thailand (1978-99), (RFD, 2000)........................10

Figure 2: Economic importance of species (Production in m3, RFD 1992) (for species code refer to Appendix 1)...............................................24

Figure 3: Local farmers "fake house" ..............................................................25

Figure 4: Map of Thailand and the study area Huay Kha Khaeng......................27

Figure 5: Research area at Huay Kha Khaeng, at the Song Thang valley. View from the southern ridge, with the bordering western ridge.........30

Figure 6: Mean monthly precipitation at Huay Kha Khaeng (1980-95) .............33

Figure 7: Annual Precipitation at Huay Kha Khaeng, Thailand (1980-1995).....................................................................................34

Figure 8: Outline of temporary plot design, representing Baseline 2..................40

Figure 9: Temporary Plot................................................................................41

Figure 10: Species curve over all samples (76 plots).........................................48

Figure 11: Dominance-types as derived from cluster analysis of the data DBH ≥ 5 cm ....................................................................................49

Figure 12: Group-structure of sample plots as derived from cluster analysis of the data DBH ≥ 5 cm.......................................................50

Figure 13: Position of individual species (horizontal axis = dimension 1, vertical axis dimension 2); CA of basal-area data for trees ≥ 5 cm DBH ..........................................................................................51

Figure 14: Position of the 5 permanent plots in relation to all temporary plots ..............................................................................................53

Figure 15: Permanent plot design.....................................................................57

Figure 16: Hemispherical Photograph, taken in the Mixed Deciduous Forests.............................................................................................59


VI

Figure 17: Available amount of light in PP1-5 and the 2ha plot......................... 60

Figure 18: Light map of the 2 ha plot............................................................... 60

Figure 19: Bore core sample of Shorea obtusa.................................................. 62

Figure 20: Species distribution in the DDF- plots PP1-3 ................................... 65

Figure 21: Species distribution in the MDF- plots PP4 + 5 and the 2ha plot....... 67

Figure 22: Distribution of all individuals across the Social Position .................. 69

Figure 23: Distribution of main DDF species across the Social Positions........... 70

Figure 24: DBH Distribution across all DBH classes........................................ 72

Figure 25: Crown maps of all plots representing the real crown radii................. 78

Figure 26: All individuals of the 2ha plotted by their X and Y coordinate with appr. 130 potential crop trees across the whole stand. ................ 80

Figure 27: Distribution of Potential Crop Trees-PCT’s across the DBH range .............................................................................................. 81

Figure 28: Comparison of the height curves of selected MDF species................ 97

Figure 29: Diameter increment of selected species............................................ 99

Figure 30: Changes in stem number diameter distribution in the first (year) prognosis period .................................................................. 103

Figure 31: Stem number diameter distribution of removal stand...................... 105

Figure 32: Mixed Deciduous Forests, picture taken during a helicopter flight in May 1997......................................................................... 149

Figure 33: Cycus siamensis in a fire affected DDF stand ................................ 151

Figure 34: Previously logged and fire affected DDF stand .............................. 152

Tables

VII

Tables

Table 1: Decrease in Forest Area (Selected Years)..........................................13

Table 2: Timber value of selected species.......................................................24

Table 3: Results of the floristic inventory .......................................................45

Table 4: Relative abundance (%) of the five most abundant species per diameter group and their presence in other groups.............................46

Table 5: Distribution of all individuals across the DBH-classes, represented as %/plot ......................................................................73

Table 6: Development of the Basal Area from 1995 to 1997 ...........................74

Table 7: Volume (solid volume over bark) in the permanent plots ...................76

Table 8: Basal area and percentage of individuals represented as potential crop trees,........................................................................................83

Table 9: Selected species for calculating stand height curves...........................94

Table 10: Results of the non-linear regression fitting the stand height curves for MDF species....................................................................95

Table 11: Regression results of the increment functions ....................................98

Table 12: Volume increment table for the 2ha plot, all individuals .................. 102

Table 13: Volume increment for the potential crop trees ................................. 104

Table 14: Volume increment table for the 2ha plot, competition and bad quality trees removed ..................................................................... 106

Table 15: Differences in structure and occurrence of DDF and MDF............... 111


VIII

Abbreviations

Appr. Approximately

AP Aerial Photographs

ACV Asymptotic Confidence Interval 95%

b.a. Basal Area

CA Correspondence Analysis

CL Cluster Analysis

CSEA Central South East Asia

DBH Diameter at Breast Height

DDF Dry Dipterocarp Forests

dpi Dots Per Inch

ETFP European-Thai-Forestry-Project

FAO Food and Agriculture Organisation

GPS Global Position System

HKK Huay Kha Khaeng

MDF Mixed Deciduous Forests

MSE Mean Square Error

NWFP Non-Wood-Forest-Products,

n.a. Not Applicable

PCA Principal Component Analysis

PCT Potential Crop Tree

RFD Royal Forest Department

RTG Royal Thai Government

Summary

IX

Summary

In 1938 more than 70% of Thailand was covered by forest, in total 35 million

hectares of vital forest. Of this, less than 20% remains. Large scale commercial and

illegal logging can be held responsible on the one hand with the growth of urban

areas and industrial estates on the other . Today, natural forest can only be found in

very remote areas or in areas under protection. Remaining forests are suffering

varying levels of degradation. Due to a logging ban, imposed by the Royal Thai

Government, no commercial logging schemes exist, with the exception of Mangrove

forests. The forests are more or less left alone without any silvicultural management .

The aim of this research was to assess the structure and composition and the growth

and yield of the forests under consideration. Subsequently, their silvicultural

potentials were estimated and future prospects and potential for semi-natural

silvicultural management investigated.

The main focus of the research was:

• To identify and classify prevailing forest types through the analysis of aerial

photographs.

• To establish temporary research plots to assess species distribution, composition

and community structure.

• Establishment of long-term observation plots to assess growth and yield.

• Assessment of the silvicultural potential of selected forest types.

Identification and classification of forest types via aerial photograph analysis

The analysis of aerial photographs served to identify main topographic features and

resulted in the delineation of 4 main forest types in the research area. Ground surveys

revealed the mosaic and heterogeneous structure of the forest.


X

With this survey the two main forests types under consideration, the Dry Dipterocarp

(DDF) and the Mixed Deciduous Forests (MDF) could be distinguished in different

stages of disturbance. Due to the mosaic structure of the forests, line sampling was

chosen for the set-up of a series of temporary plots, placed in their respective forest

types for the following assessment.

The analysis of aerial photos produced satisfactory results, considering the quality

and scale of the pictures.

Establishment of temporary research plots to analyse species distribution,

composition and community structure

A set of 76 temporary plots were selected by line sampling. On the basis of cluster

and correspondence analysis, two forest types could be characterised and their

structure and dynamics assessed. As a result, species area curves could be described

and different forest sub-types identified. Species composition and structure supported

their classification into xeric and mesic forest types.

Establishment of long-term observation plots to assess growth and yield

Aiming to establish long-term observation sites, a series of permanent plots was

created. Their placement was verified by correspondence analysis.

The assessment of the Dry Dipterocarp (DDF) and the Mixed Deciduous Forests

(MDF) revealed considerable differences in respect to growth and yield:

• Species composition in the DDF is dominated by two main Shorea species. In the

MDF up to 10 species co-dominate.

• Stem density is considerable higher in the DDF.

• Diameter range of the DDF is limited to below 50 cm DBH; MDF stands can

hold diameter ranges up to 80 cm DBH.

• Stand structure of the DDF is open, with small crowns, in comparison to the

MDF which hascontinuous cover with small gaps.

Summary

XI

• DDF is two layered and MDF three layered.

• Basal area and volume of the DDF is 20 to 30% lower, compared to the MDF.

• Assessment of potential crop trees revealed a patchy distribution in both forest

types, with a restricted potential for silvicultural management.

• Regeneration continued at effective levels in both forest types.

Assessment of the silvicultural potential of selected forest types

Based on DBH, height and crown diameter relationships, dependencies were

investigated. Species-specific differences in respect to the above parameters could be

revealed. The results were used for a limited growth prognosis. The growth

prognosis revealed an annual volume increment of 5 m3/ha, which is quite

considerable for a natural Mixed Deciduous Forest. Applying semi-natural

silvicultural techniques by selecting potential crop trees for liberation and the

subsequent refining of the stand resulted in an apparent volume growth reduction to

3.4 m3/ha. However, because of the lack of knowledge regarding the response of the

potential crop trees to liberation, their increment was set to be linear. It can be

assumed that the vital crop trees will respond positively to their liberation and

increase their increment in the long-term , recuperating the loss in yearly increment.

As a result of the growth prognosis, two different management schemes seem to be

advisable. Depending on structure and state of disturbance, high intensity and low

intensity semi-natural management schemes can be suggested to address the need for

economically feasible and sustainable future management.

Implications

Considering the present state of forestry in Thailand, the need for suitable and

sustainable future silvicultural management becomes evident. The remaining forests

are increasingly under the threat of illegal logging or encroachment and are legally

sacrificed to urban and industrial development. The Royal Thai Government and all

institutions involved have to participate to protect their forest resources and utilise


XII

their potential. Investments should be made now to maintain and improve the

remaining forests and to carry out a detailed nationwide inventory. Once the status of

the forest resource is assessed, the potential for silvicultural management should

become clear and sustainable management plans can be developed.

Introduction

1

1 Introduction

Early visitors to Thailand and the surrounding countries described it as “... a land of

undisturbed and healthy forests and rivers full of fish and people living in harmony

with their environment....” (CARNÉ, 1866). They also described the forests as a

fragile ecosystem under constant threat from shifting cultivation and other types of

land use (CREDNER, 1935).

Today, a totally different picture prevails. In recent decades, intensive logging and

agricultural expansion has led to the continuing exploitation and loss of large tracts

of natural forests in Central Southeast Asia (CSEA) (FAO, 1997). Once healthy

forests are now degraded and turned into secondary forests at differing levels of

disturbance. They cover large areas, with wide-ranging ecological, climatic and

hydrological effects, with a powerful impact on the economy, both locally and

nationally. In many cases, the opportunities for rural families to provide for their

basic requirements and to gain for income generation are diminishing

(ARBHABHIRAMA, 1987; POFFENBERGER, 1990).

Deciduous forests are particularly affected from such processes due to the ease with

which they can be converted into agriculture land and because fire can be easily

applied as a tool for land clearing.

Existing law also prohibits construction on forested land. This can be overcome by

illegally burning the forest, turning the area into degraded land. This new status

makes construction possible. As “degraded land” is turned into property and

becomes an economic asset it gives investors and construction companies access to

state subsidies. This process is often supported by the politicians themselves who,

tempted by the low risks and high returns involved, have transformed large areas of

forest near major cities into industrial estates, housing and recreational areas such as

golf courses and theme parks. Corruption and cronyism are an important element

here.


2

Fire is also widely used by the rural population, firstly as a tool to drive game for

hunting and secondly to burn dry grass to allow new growth on grazing lands.

Cleared ground is also considered a pre-requisite for the collection of mushrooms,

herbs and other minor forestry products.

When the factors mentioned above are applied locally, major fires can be started

which ultimately affect a whole region. Of the estimated 530 million ha deciduous

forests that exist globally, about one third burn annually (GOLDAMMER, 1993;

JONES, 1997). In the case of Thailand, the imminent forest destruction was foreseen

decades ago (LÖTSCH, 1958). However, despite the great number of trained forest

personnel now working, the situation has worsened rather than improved, which is

attributable to corruption, inadequate silvicultural management and rapid population

growth. Depending on the data source cited, of the estimated 70% forest cover that

existed around the turn of the Century, today only about 15 to 26% remain

(LEUNGARAMSRI and RAJESH, 1992; ROYAL FOREST DEPARTMENT,

1996). The Food and Agriculture Organisation (FAO) of the United Nations

estimated 22.8% in 1997 (FAO, 1997).

Of the remaining forests, over half are deciduous. Many of the fire affected and

cleared areas are subsequently invaded by herbaceous species like Imperata

cylindrica and Eupatorium odoratum. If no controlling measures against their

invasion are taken, they will inhibit the natural establishment of tree regeneration for

decades (KETUPRANEET et al., 1986; STOTT, 1991).

Current politics and law advocates a strict functional and spatial separation of

productive and conservation forests. However, considering the scarcity of land and

forest products, in the long-run this will not be enough to cater for the needs of the

population and for the industrial sector. Conventional reforestation through

replanting programmes has mostly failed, due to both environmental conditions and

management short-comings.

Introduction

3

In this context, semi-natural silviculture of existing stands, no matter how degraded

they are, has emerged as a promising alternative. The concept is based upon a

reliance on autochthone species, but depending on which species are needed, their

actual proportions might be altered as compared to natural forests. As in the case of

conventionally managed productive forests, trees with desirable trunk and wood

properties are favoured. At the same time, one relies as much as possible on natural

dynamics, such as regeneration processes and natural forest structures.

Semi-natural silvicultural management has many ecological, managerial and

economical advantages:

• Biodiversity and ecological stability can be retained and even improved on

degraded land

• the product range is wider than with plantations

• improved management may support self sufficiency in high quality natural timber

• it may cater for a wide range of consumers, in particular where subsistence

farming in the vicinity of forested land is an issue

• improving natural forests can be more cost efficient. It may also be a less risky

approach compared to the establishment of plantations. Enrichment planting with

a mixture of autochthone species can be less costly to establish than plantations.

Market dependency associated with a single or a few species used in plantations

can therefore be reduced.

On the other hand, semi-natural silviculture is demanding with respect to

management skills and the understanding of the ecological and social context.

Successful and sustainable semi-natural silviculture requires profound knowledge of

the structure, growth and functioning of natural forest ecosystems and the autecology

of native species (BURSCHEL and HUSS; 1997). The present management - more

aptly mismanagement - of the remaining forest resources in Thailand has to be

transformed in order to support Thailand with a valuable and marketable resource.


4

In the light of the above, the following work will give an introduction and review of

the forest management of the past and present in Thailand. An assessment of

composition, growth and yield of two selected forest types will follow, concluded

with an assessment of the potential and possibilities for future silvicultural

management.

Problem statement and research outline

5

2 Problem statement and research outline

2.1 General problem statement

Though there is a long tradition of forest utilisation and timber trade in the region

(VILLIERS, 1965), only with the onset of the colonial era did the forests become

an economic asset in a modern sense. Chronologically, this coincided with early

silvicultural developments that took place in Central Europe during the early 19th

Century (BRYANT, 1994).

Though the British colonial administration and timber industries - concerned with

sustaining the FLOW of raw material - had a temporary relief with the first

annexation of the lower parts of Myanmar in 1826, they began to adopt systematic

and scientifically-based forest management practices. Minimum diameter-based

selection systems on a rotational basis were introduced for the exploitation of

forests. Focus was mainly on two deciduous forest communities:

• the Shorea robusta dominated dry dipterocarp forests (Sal) of the Indo-Myanmar

region

• and the Tectona grandis bearing mixed deciduous forests of Southeast Asia

(BRYANT, 1994; VILLIERS, 1965).

It remains questionable whether this was due to their esteemed wood quality or

because the species have a natural tendency to occur gregariously which rendered

them suitable for the selection and silvicultural converting systems introduced.

TROUP (1921), already criticised this approach for its lack of sustainability,

stressing that a less schematic, more ecosystem-specific silviculture was required.

From a scientific and political point of view, a natural evolution from elementary

botanical and descriptive work to research on functional aspects could be observed,

later succeeded by intensive discussions about the direction forestry and silviculture


6

should take. Regarding deciduous forests, discussion centred around the controversy

of how to deal with fire with respect to the long-term dynamics it induces:

• on one hand there were the supporters of a silviculture which maintained the

anthropogenically conditioned fire sub-climax communities with their high

proportion of - under the premises of the era - valuable species (Sal, Teak),

• on the other hand there was a group that favoured a silviculture allowing forest

communities to drift toward their edaphic and climatic optimum - with a strong

control of fire

Around 1900, the Indian sub-continent was more or less covered with complete

forest floras. Important overviews are given by DYER (1874), ROXBURGH (1874),

KURZ (1877), BRANDIS (1884, 1906), and HEIM (1902). The publication of “The

silviculture of Indian Trees” (TROUP, 1921) marked the beginning of a shift from a

descriptive to an analytical phase in research and subsequently laid the foundation

for a silviculture that could be based on ecosystem characteristics and the ecology of

involved species. This monumental, three-volume publication covered around 1000

species typically found in the Indian sub-continent. Another mile-stone was the

publication of “A preliminary survey of the forest-types of India” (CHAMPION,

1936). Though the rough structures had already been outlined by TROUP, it was

CHAMPION’s work that provided the necessary guidelines to define and delineate

forest communities, fundamental for site-specific silviculture.

The inter-war years saw a steady increase in the number of publications and their

scope. As before, it was the Indian sub-continent that led the discussion. A prime

subject was the natural and artificial regeneration of Sal and Teak forests, an

indication that the exploitation of natural forests was coming to an end and

silvicultural answers were in need (BARRINGTON, 1931; CHAMPION, 1931;

SMYTHIES, 1933; MILROY, 1936; SENGUPTA, 1939; SMYTHIES, 1939;

KERMODE, 1944; NAIR, 1945). As mentioned above, closely linked to the subject

was the issue of fire and its effect on regeneration and stand dynamics (DAWKINS,

1921; TROUP, 1921; MILROY, 1930; SHEBBEARE, 1930; CHAMPION, 1936).


7

In other countries of the region attempts at systematic forest management began

much later. In Thailand, a central forest administration was only founded in 1896,

following the Indian management example. Even later the French colonies followed

suit. The first floristic inventories of Thailand (RYAN and KERR, 1911;

GAIRDNER, 1915; CRAIB, 1925) appeared nearly half a generation later. In

Indochina work was begun still later. Examples of early work include LECOMTE

(1926), MAURAND (1943), and later works by ROLLET et al. (1952) ROLLET

(1953, 1972), and VIDAL (1956, 1959, 1960).

In Thailand, the mandate for silvicultural management was held by the Royal Forest

Department, however they had no power of enforcement. The initial Brandis

(Selection) System was modified in 1919 (BOONYOBHAS, 1961;

BANJIBATANA, 1962/A, 1962/B), and continued to be in place until 1989 when a

complete “logging ban” was declared. Research was neglected, the ecology and

silviculture of natural forests had seen little of value published until well after

W.W.II. The catalysing event might have been an inventory conducted by the FAO

in 1958 (LÖTSCH, 1958). It drew a depressing picture of the conditions of the Teak

forests and predicted a complete collapse of the forestry sector if management

practices were not fundamentally altered. Since then, there has been a gradual

increase in research, but considering the ecological and economic importance of

deciduous forests, even today few studies and publications deal with deciduous

forests and their silviculture and even less has been published about evergreen

forests.

Various authors have published floristic accounts of Thailand, with strong focus on

the Family DIPTEROCARPACEAE, culminating in the work of SMITINAND

(1980). A series of publications dealt with:

• species nomenclature and the problem of vernacular names (RFD, 1948;

WINIT, 1960; SMITINAND, 1980),

• description of timber species (SONO, 1974; TONANON, 1974, 1996),


8

• generic descriptions of the forest-types of Thailand (MAHAPHOL, 1954;

OGAWA and KIRA, 1961; RFD 1962; SUKWONG et al., 1974; 1982;

STOTT, 1988; BANGKURPOL, 1979; RUNDEL, 1995).

With regard to dipterocarp forests, functional aspects (including fire ecology) were

approached only in recent years by:

• (POKAEW and ELLIOT, 1994; KANJANAVANIT, 1992; KETUPRANEET

et al., 1991; SUTTHIVANITCH, 1989; SUNYAARCH, 1989;

SATHIRASILAPIN, 1987; STOTT, 1986; 1988; 1990; SUKWONG et al.,

1977),

• crown structure and light and gap pattern (BUNYAVECHEWIN , 1983, 1986;

DHANMANONDA, 1988; 1995),

• natural regeneration, seed dispersal, harvesting times (KHEMNARK, 1978;

DHANMANONDA, 1992; RFD, 1986; Wong, 1992),

• biomass (Mc. Neal, 1967; SABHASHRI, 1967; KUTINTARA, 1977;

WANUSSAKUL, 1989) (the work of NEAL and SABHASHRI served

military/forensic purposes),

• population structure of dry dipterocarp forests (KUTINTARA, 1975;

BUNYAVECHEWIN , 1985; HIGUCHI, 1986; SAHUNALU, 1995),

• community transitions, gradients and succession (BLASCO, 1983;

BUNYAVECHEWIN , 1985; THUAMSANG, 1983; THITATUMMAKUL,

1985).

With respect to the autecology of individual species, except Teak and to a lesser

extent the xerophilous Dipterocarp species, there exists little published information

despite work in progress (ELLIOTT, 1995). Exceptions are SUKWONG et al. (1975)

and SUKWONG and DHAMANITAYAKUL (1977); and ELLIOTT et al. (1994).


9

A key-limitation of most studies is that they are extremely local in character. A large

number of investigations refer to a single research site (Sakaerat Experimental

Station, Korat Province), a fact that further constrains the value of information.

Parallel to the above, research on deciduous forest ecosystems in India has made

substantial progress in recent decades (TEWARI, 1995), though it remains open

whether this knowledge can be extrapolated directly to a Thai situation. No long-

term data exist on silvicultural experiments such as thinning and tending in

deciduous forests in Thailand due to the above described management practice of the

past. In summary, there is insufficient knowledge to provide a basis for applied

silviculture and an urgent need for site-specific research.

2.2 Research needs

The remaining forest areas in Thailand need to be put back into production or

under conservation. The vast amount of land covered by degraded forests and

other areas not suitable for agriculture at present needs to be investigated for its

suitability for plantations. The species composition should include a mix of native

species and of timber species in demand commercialy, to encourage local and

international investors with the prospect of an adequate return on their investment.

The necessary shift in policy and research should also be triggered by the ever

increasing demand for timber and the diminishing supply from neighbouring

countries. The latest years show an actual decrease in imports, due to the

economical crisis in Asia, but is increasing again as can be seen form the 1999

figures.

Neighbouring countries will not be able to provide sufficient timber indefinitely.

They can only support the shortfall for a short period of time. Under the present

economic crisis, where foreign currency is scarce, imports, paid for in US$, are

expensive and need to be reduced to a minimum. The long term aim should be to

supply the market with valuable timber from their own resources to gain

independence from outside markets in the future


10

Figure 1: Import of timber to Thailand (1978-99), (RFD, 2000)

The Royal Forestry Department of Thailand has neglected silvicultural research in

the past. The main focus of research was given to still existing Teak (Tectona

grandis) and Pine (Pinus mercusii, P. kerrii) forests in the northern part of Thailand.

For those species yield tables have been developed. However, for the other species

no valid data on growth and yield exist. Apart from a few research projects in natural

forests, the RFD focussed mainly on plantations of Eucalyptus and other fast

growing species. There is a definite lack of the long term silvicultural research plots

needed for an effective long-term data base on growth and yield.

2.3 Aim of research

Given that the rapidly increasing population in Southeast Asia will put more pressure

on land and forests, there is a need for sustainable management of the forest

resources that remain. Urbanisation and the subsequent unlimited growth of cities

destroys valuable farm land, resulting in illegal encroachment into forests. Radical

Timber Import (1978 - 1999)

1978

1979

1980

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

[m3 x 1000]

0

500

1000

1500

2000

2500

3000

3500

4000


11

conservation of the remaining forests and insufficient plantation schemes will not be

enough to supply the high and diverse demands of the rural and urban populations as

well as the industrial sector. In addition, timber and commodities made from wood,

formerly supplied by neighbouring countries, are diminishing at an ever increasing

rate with corresponding price rises.

One question remains, what management is required to rehabilitate and utilise

deciduous forests - be it for timber, Non-Wood-Forest-Products, or services - whilst

fostering, maintaining and guiding new regeneration in the desired direction? In

other words, how and in what direction to develop deciduous forests after

disturbance and will there be a possibility for sustainable management of those

forests!

Overall knowledge of the structure and dynamics of forests as well as their ecology

is extremely limited. Long term, in-depth research in silvicultural management of the

main timber species other than teak is virtually absent.. Most of the forest resources

are diminishing at a rapid pace. Without sound silvicultural management and with

continuing illegal logging, most of the forest resources left will be cleared soon.

Methods applied

1. To review literature of previous and ongoing research about silvicultural

management in the region.

2. To identify and classify prevailing forest types via analysis and interpretation of

aerial photographs and ground surveys in the selected area.

3. To establish temporary plots to assess species distribution and community

structure.

4. To establish permanent research plots and assess:

Growth and yield, quality, structure and dynamics of two main forest types.

• Soil properties by soil survey.

• Available light via fish eye photographs.


12

• Annual increment by boring analysis.

• Timber potential by selection of potential crop trees and their competitors.

5. To assess the potential of one selected forest type by simulation of possible

increment and dynamics.

Review

13

3 Review (Utilisation of forest resources in the past

and presence)

In the past, forest utilisation in Thailand was entirely in the hands of the kings and

the local regimes in the north. Forests were exploited without any permanent

management schemes but due to their abundance and the presence of small

permanent rural settlements only in the low land areas, this system did not threaten

the forest resource. With the colonial influence, especially from Britain and France

throughout the last centuries, the exploitation rate of the forests in the neighbouring

countries increased and put more pressure on the resources in Thailand. The industry

in Europe was very keen to receive durable wood, such as Teak and Dipterocarp

species from Asian countries. Prices for saw- and log-wood increased. In particular,

England, having cleared Ireland of its Oak forests during the 17th Century (MANN,

1996) and later the Oak forests of Southern England, had a strong demand for long

Teak boards to build ships.

Table 1: Decrease in Forest Area, (Selected Years) (Source: Thai Dev. Res. Institute, 1999)

Year Forest Area [sq km] Total Area [%]

1938 338,115 69 1947 316,728 64

1954 298,865 61 1961 273,628 55 1973 221,712 45

1976 198,417 40 1978 175,224 36

1983 154,444 31 1986 148,264 30 1990 139,938 28

1998 129,722 26


14

In the 18th Century Britain shifted their ship yards to India and started to build large

ships (>1,000 t) there. The high demand for railway sleepers in India, contributed

towards even greater exploitation. From 1860 until 1920, at the height of

construction, the demand for appr. 1,000,000 sleepers annually made from Teak,

Dipterocarp species and Deodar (Cedrus), contributed to the exploitation of India,

Myanmar and later also Thailand and Laos.

The Royal Thai Government requested support from the Britain colonial authorities

for the management of their forests and, after a study into the forest situation, the

Royal Forest Department (RFD) was established in 1896, headed by a British

forester. The next generations of director generals of the RFD were also British and

the policy of the department followed more or less the footsteps of the exploitation

system used in Myanmar. In 1924 the first Thai national became Director General of

the RFD, but retained the philosophy and practice of the British logging companies,

being educated at forestry schools either in Myanmar or India (THE SIAM

SOCIETY, 1989).

Early visitors to Thailand remarked in their travel notes: “...Thailand, the country

with healthy forests and full of wildlife...” (CARNÉ, 1866). CREDNER in 1927,

wrote that approximately 60% of Thailand was covered by thick forests. In 1961 it

was estimated to be roughly 53% and by 1996 the RFD put the figure to appr. 25%.

It may well be less than 15% by now.

Mistakenly the forests were seen as an unlimited resource and the absence of long

term silvicultural management systems can be seen as a main cause for the present

state of the forests in Thailand and in many other countries of the region.

3.1 Concessions

As described above, most of the forested land has been, and still is, under threat of

logging. In the past the local communities were not involved in the concession

business, except as mahouts and as local staff for the English field officers or to the

Thai concession companies, such as the Thai Plywood Company today.

Review

15

The Royal Forest Department issued concessions for teak in the north of Thailand in

the late 19th Century and large scale exploitation started, mainly by European logging

concessionaires.

Large areas, very often whole watersheds or catchments as large as a 1,000 square

miles, were given as concessions (CAMPELL, 1935) and the so called “Teak

Wallah”, an expression for the foreign field officer, was in charge of the field

operations spending months out in the forest. Teak trees with more than 60 cm girth

were counted and girdled during the beginning of the rainy season. After two years

they were dry enough to float and could be felled. After felling, the logs were coded

with a numbering hammer: the different numbers indicating the initials of the

company; the year of felling; the identification number for the field officer in charge

and the timber classification. Elephants were used to drag the logs to the nearest river

and there they would wait for the next rainy season to be floated towards Bangkok.

In some areas even small railways were build (CAMPELL, 1935) to transport logs to

the nearest river draining into one of the tributaries of the main river Mae Ping. The

average time taken for a log to reach the saw mills in Bangkok was 5 years. Entire

watersheds were exploited for their timber and have never recovered.

The foreign influence ceased after World War II and local and regional concession

companies filled this gap. By 1969, about 516 concessions were granted

(LEUNGARAMSRI and RAJESH, 1992), covering about 50% of the total land area.

During the next 10 years forests were destroyed on a large scale and suffered heavy

losses.

When the Royal Thai Government decided to reduce logging after pressure by

environmentalists, it put 50% of the former logging areas under protection, although

the damage was already done and left appr. 6 million ha of degraded forests. This

protection scheme did not last long and in 1984 large areas were opened again to

logging companies.


16

In 1988 heavy rain resulted in severe floods and land slides. More than 350 people

were killed by illegal and legally logged trees, swept downhill into villages by the

floods in the southern provinces.

This finally prompted the Thai Government to revoke all concessions, except for

Mangrove forests, and to declare a total logging ban in 1989 to put the forests under

protection.

Loss of forests after the logging ban

Unfortunately, even with the logging ban in place, illegal logging still occurs. As the

price of timber increased immediately after the declaration of the logging ban, the

pressure on the forest did not cease. There are a number of ways to extract timber

and bypass the logging ban:

• Thailand has increased its logging activities in neighbouring countries, especially

in Myanmar, Laos and Cambodia. Illegally cut logs from Thailand, when

controlled at the few highway check points, can easily be declared as originating

from one of the above countries.

• Legally cut timber, resulting from one of the many dam and reservoir projects in

Thailand can be “mixed” with illegally cut trees.

• Large scale resettlement projects such as the Green Isarn Project (Kor Jau Kor)

covering five north eastern provinces and backed by loans from the World Bank

and the FAO (1992), convert native forests into commercial tree plantations with

fast growing species.

• Thailand’s border areas and the national parks are still very remote and

difficult to control, hence illegal cutting is common and continues especially in

the present economic crisis, leading to incidents like the most recent at the

Salween National Park close to the Myanmar border, where large numbers of

illegally cut logs were found. This might force the Director General and other

Review

17

responsible officers of the RFD out of office, but in general has no impact on

the illegal cutting.

• Local farmers are paid relatively high wages to cut trees and instantly process the

timber in the forest. The boards can then be carried away easily and local furniture

makers or timber factories will buy it.

• Timber traders also pay villagers to cut down trees and later tip off foresters, who

then confiscate the logs. They are stored at a RFD site and then auctioned and sold

at low prices, now legally, to the very trader who paid the villagers to cut them

down! Obviously, this can only work with a great deal of participation

bygovernment officials.

• Cash crop promotion by the Thai Government leads to increased destruction of

forested land, whether natural or already degraded forests.

• Loss of Mangrove Forests due to an increase in prawn and shrimp farming. From

1979 until 1989 more than 37% of the total mangrove forests have been destroyed

(they are exempt from the logging ban!) by continuing large scale aquaculture.

• Golf courses and recreational facilities add immensely to the destruction. A study

by the Social Research Inst., Chulalongkorn University (1992), asserts that

between 13 and 26% of the golf courses in Thailand are on land officially declared

as forests. In total there are more than 400 golf courses planned in Thailand.

• The rural population is allowed to extract timber for building farm houses. After

they have build them, some are left unoccupied for a few years and then floor

boards; booms and poles are sold to local traders.

3.2 Plantations

Thailand started its first large scale teak (Tectona grandis) plantation scheme in

northern Thailand in 1906 (KAOSA-ARD, 1995). In 1965 the Teak Improvement


18

Centre in Ngao, Lamphun, was set up and first supported with Scandinavian aid and

later also by multilateral international projects. The teak plantations now cover appr.

170,000 ha (KAOSA-ARD, 1995). In 1996 the RFD estimated the total area of

plantations to be appr. 8,700 km2 of the total land area of 513,115 km2. The FAO

estimated 529 km2 ha to be plantations in 1995 (FAO, 1997).

International efforts to increase plantations, such as the Tropical Forestry Action

Plan (TFAP) had a high impact on Thailand. The Thai Government decided to

increase their forested land to 40% and issued a bill (Thai Forestry Sector Master

Plan, 1993) to support this.

The main tree species promoted is Eucalyptus camaldulensis. In order to benefit

from this scheme, business investors and multinational corporations supported forest

destruction and illegal logging of native forest, because only when forest land could

be declared degraded could they move in with large scale plantation schemes and

collect subsidies.

This led to large scale destruction of forests beginning in the early 1980’s. In 1990

five paper mills, eight Eucalyptus plantation projects and twelve wood chip

companies received privileges from the Board of Investment and more are still

asking for permission. Some of the reforestation projects like the Green Isarn

required more than 1.2 million ha of Eucalyptus plantations, resulting in a

devastating impact on the remaining natural forests.

Subsequently, farmers who formerly lived in the natural forest were forced out of

their areas and onto other forested land outside the reforestation schemes. Due to the

scarcity of land those areas are often inside national parks or wildlife sanctuaries and

put even higher pressure on the environment.

Review

19

3.3 Management systems of the past

Thailand has clearly lacked a long term silvicultural management system in the past.

Most of the surrounding countries have some tradition of developing their own

silvicultural management systems (LAMPRECHT, 1990) such as the

• Malayan Uniform System – MUS –

• Tropical Shelterwood System – TSS –

• Philippine Selective Logging System – PSLS –

• Taungya System

These systems were often introduced by the former colonial powers and later

adjusted and improved by local forest authorities. It is noteworthy that even a system

like the Taungya system, developed by Dietrich Brandis, a German botanist and

forester, mainly as a conversion system to replace natural forests with Teak (Tectona

grandis) plantations in Myanmar and obviously well suited for Thailand, was

established in Thailand only for a short period of time at the beginning of the last

century.

There were 3 types of rotation (KAOSA-ARD, 1997):

• long term: > 30 years for Tectona sp., Pterocarpus macrocarpus and Xylia xylocarpa

• medium term: between 10 and 30 years for i.e. Tectona sp., Pinus sp. and Azadirachta sp.

• short term: < 10 years (small poles, pulp wood, fire wood, etc.) for Eucalyptus sp., Acacia sp., Casuarina sp. and Bamboo sp.

After World War II, the RFD tried to introduce a Selection System for Teak and

Non-Teak-Forests, a Strip Clear Cutting System for mangrove forests and the so-

called Clear Cutting System for bamboo forests.

Unfortunately, the concession holders concentrated on extraction with little emphasis

on reforestation. As there was limited control during and after logging operations,


20

unclear concession boundaries and a lack of detailed maps, it was common place for

the logging companies to blame local villagers or ethnic minorities for the

destruction, who later moved into the cleared areas.

Despite the successful development of permanent management schemes by British

companies in India and Myanmar, Thailand did not benefit from such systems. Not

even when British logging companies were present in Thailand, did they put a high

effort into developing a permanent management scheme.

The large scale rubber plantations (Hevea brasiliensis) in the south of Thailand were

never intended to produce timber, however in the last 5-10 years the timber has been

used for furniture and small household items.

In the absence of sound management systems to reforest or regenerate timber

resources, Thailand relied heavily on their natural forests. The only exceptions were

some Teak plantations in the north and Eucalyptus in the north east.

3.4 Present management systems

As described above, Thailand introduced a near complete logging ban (except for

Mangrove forests) and all concessions have been revoked. Even for research

purposes it is prohibited by law to cut a single tree. The Royal Forest Department is

trying to either convert natural forests into conservation areas or into plantations. In

both cases the disadvantages of such a narrowly focussed approach are clear:

• Not all natural forests are of sufficient value for strict conservation. Many of

those areas, especially when traditionally protected by the local population, could

be used in one or another type of silvicultural management, either by the state on a

macro level or under local management or both.

• It is economically unfeasible for a densely populated country like Thailand to

keep too much of their total land area under strict conservation. Present

discussions centre around 20-25 % of the total area.

Review

21

• Many forests which by law are declared as degraded forests and therefore suitable

for plantation, are in fact forests with sufficient potential to be managed. The

process of clear cutting this valuable resource and reforesting later with

monocultures will lead to a loss of biodiversity and natural beauty. It is also not

viable on the macroeconomic level and in addition facilitates large scale

corruption as previously seen.

It can be argued that the present approach could help to protect the few natural

forests remaining but given the success in protection from the Royal Forest

Department, this is questionable, and they are certainly struggling with national as

well as local politicians and influential business people.

For many years Thailand has tried to establish a Community Forestry Law which

could help overcome some of the problems described above. The intention is that

local communities, together with forestry officials and the rural administration,

develop management plans together enabling them to use the forest resource.

Unfortunately this law is still blocked by influential parties trying to establish their

enterprises before a community forestry law halts the destruction of the forest.

A sound silvicultural management system for forests at different stages of

degradation, together with a community forestry act implemented at the local level, a

clear plantation and reforestation scheme and a sound conservation law could all help

to protect the remaining forests and to put some of the forests back into production.

3.5 Thai Forestry Master Plan

At the end of the 1980’s, external pressure was exerted by foreign and public

organisations to change the attitudes of Thai politicians and foresters towards forest

exploitation. This coincided with the realisation that the forest resource was

diminishing rapidly. A result of this was the development of the Thai-Forestry-

Master-Plan draft.


22

The master plans focus’ on the conservation of existing forest resources, together

with improved management of non-forested areas, respectively degraded forests.

The goal is to become self sufficient in most timber products, to improve the

supply of raw material of the wood-based industry and to avoid exports of

unprocessed round wood or raw materials.

Rehabilitation of Thailand’s main watersheds in the North is another big issue,

followed by invalidating all existing logging concessions.

An increased involvement in planning and managing of the forests by the public

and the local communities (community forestry) in basically all forestry related

topics is envisaged. A consequence will be a substantial alleviation of power of

the central government and the forestry department.

In principle all parties agree with the Thai Forestry Master Plan. However, all

political parties in power over the last decade have had strong ties to the forestry

sector and connections to the local timber trade, whether legal or illegal.

Therefore strong vested interests have succeeded in blocking the Master Plan.

So far, no political party has been sufficiently strong or independent to realise the

Master Plan or to get approval for the community forestry law by the cabinet.

3.6 Previous inventories

There is no record of previous national inventories in Thailand. There was no

attempt made in the past to cover all of the forested land with an inventory to

provide qualitative and quantitative information about the national forest

resources.

Whenever an inventory was carried in Thailand, it was on a regional or local

scale, focussing on selected species and it was always very aim specific. This can

be seen with the inventory carried out by Lötsch (1957) which mainly focussed on

the distribution of one species, Teak.

Review

23

In 1967 the US Army (MC NEIL, 1967) carried out a biomass inventory in

Thailand, to find out how different forest communities react to different sizes of

shell and other anti personnel devices. The inventory was also intended to reveal

information on biomass.

In the late 70’s the RFD (AATHUIS, 1990) used satellite data to map the forests

in all main watershed areas in the north of Thailand. The aim was to develop a

country-wide watershed classification, allowing areas to be delineated in areas

with high agriculture potential and others for strict conservation. With this

classification the RTG received a legal instrument to drive ethnic minorities and

other unwanted communities out of the forest.

During the late 70’s and 80’s, local inventories were carried out by Sukwong

(1975), Kutintara (1975), Bunchavetchevin, (1983, 1985, 1986) mainly to assess

the structure and biodiversity of specific community types.

Inventories providing data on forest resources for policy decisions and long term

national and regional forest management planning (AKCA, 1997) are virtually

absent in Thailand. Multi resource inventories for land use planning, habitat

management, recreation etc. are only now beginning to be part of the regional

planning scheme.

3.7 Species importance for the regional timber trade

In Figure 2, the main timber species and their importance, with respect to the

amount harvested and processed in 1991, are shown.


24

Timber harvest in 1991 [m3 * 1000]

50 150 250 3500 100 200 300

SHOROBTU

XYLIXYLOLAGECALY

PTERMACRAFZEXYLO

ANOGACUMDIPTOBTU

IRVIMALA

EUGECUMISHORROXB

TERMCORTTERMALAT

TOONCILICHUKVELU

LAGETOMETERMBELL

GARUPINNTERMNIGR

DALBOLIVDILLENI1

SINDSIAM

VITEPINNOthers

Figure 2: Economic importance of species (Production in m3, RFD 1992) (for species code refer to Appendix 1)

Shorea obtusa, one of the main DDF species is shown to have the highest figures.

More than 310,000 m3 were legally harvested in Thailand in 1991. Xylia xylocarpa

and Pterocarpus macrocarpus are sought after in similar quantities. Table 2 shows

the increase in timber prices from 1992 to 1996. Hard woods, such as Afzelia

xylocarpa, Pterocarpus macrocarpus, Walsura villosa and Schleichera oleosa, also

regarded as main timber trees are categorised as the “Hard Wood (Mixed)”. Sindora

siamensis, a species in high demand is renowned for its excellent timber quality and

durability.

Table 2: Timber value of selected species (Forestry statistics of Thailand, RFD 1966)

Species 1992 [US $/m3] 1996 [US $/m3]

Hard wood (Mixed) 283 515-785 Shorea obtusa, S. siamensis 558 785 Anogeissus acuminata 558 785 Xylia xylocarpa 566 839 Sindora siamensis 729 1475

Review

25

Figure 3: Local farmers "fake house"

The price of hard wood in Thailand nearly tripled during that period and is still

increasing. In 1991, 3 years after the logging ban there were still large amounts of

timber sold from previously harvested concession areas. Afzelia xylocarpa, a species

of supreme quality for furniture making was already in very high demand in

Thailand, being imported in large quantities from neighbouring countries. All of the

species listed can be found in one or more of the research plots, because of their

economic importance and timber quality they will be detailed in the analysis later.

3.8 Past and present influence by local communities

The highest impact in forest destruction was often blamed on local and hill tribe

communities in mountainous watersheds, due to their shifting cultivation practices.

The rate of destruction in the north was definitely high in some areas in the late 60’s

and up to the end of the 80’s. During this period the forest cover was cleared to grow

opium poppies (Papaver somniferum) and for other cash crops (UNITED

NATIONS, 1991). In the past, the ethnic minorities usually cleared only small plots

for their fields, planted their crops for one or two years and moved on to another plot,

leaving the land to recover.

As recent studies show

(SCHMIDT-VOGT, 1997)

the impact depends on the

origin of the minorities and

the cash crop they are

planting: it is impossible to

draw the general conclusion

that shifting cultivation itself

is the main cause of the forest

destruction.

Throughout the history of human settlement in Thailand fire has had an critical

impact on the forests.


26

Fire has been used for land clearing, hunting, to burn dry grass to allow new growth

for browsing of cattle, to allow easy gathering of non wood forest products such as

edible wild plants, mushrooms, small animals and also as a treatment to improve soil

fertility after clearing forest land for shifting cultivation. The latter occurred close to

the settlements and therefore was well controlled, whereas the other incidents,

especially when land is illegally cleared for commercia l purpose, often happen

without any care and control. They are largely responsible for the loss of large tracks

of forests in Southeast Asia.

In the past, illegal logging companies and whoever was involved in their business

used to destroy forest for their own profit and very often local farmers were blamed

for the destruction. Farmers are also encouraged by local traders to illegally cut logs

and to collect bamboo.

They can also ask permission of the local district authorities to cut trees for

construction and start to build a “fake” house. After a short period, usually 10 years,

the house, often more a scaffold than a house), is sold and taken apart; floor and wall

boards and poles are then sold to local business men.

The same happens with bamboo and other forest products: people are allowed to

collect small amounts for their own consumption but sell it in large quantities to

middlemen, therefore often destroying the future seed sources. The destruction of

forests by local influential people and government officials continues.

Choice of research site

27

4 Choice of research site

‘The Huay Kha Khaeng (HKK) Wildlife Sanctuary’

One of the main aims of this study was to describe and analyse the structure and

dynamics of two selected forest types. For this assessment a location had to be

selected containing relatively undisturbed Mixed Deciduous- and Dry Dipterocarp

Forests, in close vicinity with stands in different stages of degradation. The overall

objective was to cover a variety of deciduous stands, with a structure and species

composit ion representative of Thailand.

Figure 4: Map of Thailand and the study area Huay Kha Khaeng


28

Given the long history of exploitation and illegal logging, undisturbed forests are

simply impossible to find, except in protected areas such as National Parks or

Wildlife Sanctuaries.

Together with the Royal Forest Department, a Wildlife Sanctuary in Uthai Thani

Province was selected. The core area of the sanctuary has been protected since 1972,

another part was appended only recently, and was previously logged and exploited in

the 60’s and 70’s. This sanctuary covers undisturbed as well as disturbed forest

stands and was chosen as the prime research site.

Thailand’s leading taxonomist, the late T. SMITINAND regarded the sanctuary as:

“the most significant area of intact, relatively undisturbed Mixed Deciduous

and Dry Dipterocarp Forests in Thailand today” (SMITINAND, 1989).

Due to the protected status, sample and research plots can also be considered to be

relatively safe.

4.1 Location

The sanctuary is located in the western part of Thailand, roughly 300 km north-west

of Bangkok. At present the sanctuary covers 2,730 km2 in Uthai Thani and Tak

Province. Together with the adjacent Thung Yai Naresuan Wildlife Sanctuary

approximately 6,222 km2 are under strict protection, especially since being

nominated a World Heritage site in 1991.

Huay Kha Khaeng Wildlife Sanctuary, stretching from 15´48´´ to 14´ 56´´ N and

from 99´02´´ to 99´28´´ E, covers basically the entire watershed of the Huay Kha

Khaeng river which gave the sanctuary its name. This river drains into the

Srinagarind Reservoir after leaving the sanctuary. The topography is hilly with low

mountain tops, as a result of being part of the Dawna Mountain range running along

the Thai/Myanmar border. The lower parts of Huay Kha Khaeng are in the river

valley at about 150 m.a.s.l. and the highest point is Khao Khioa at 1,554 m.a.s.l.


29

The forest cover is in some parts very dense, especially where it is formed from

evergreen and mixed deciduous forests and in other parts, mainly in the dry

dipterocarp forest and in areas covered by large bamboo, it can be very open

resembling open grassland or savannah.

The area along the Thai/Myanmar border was one of the last areas settled

permanently by Thai citizens because of the remote location. Early inhabitants,

mainly hunter-gatherers and later ethnic groups practising shifting cultivation used

the area for burial grounds, rather than for permanent settlements, thereby neither

disturbing or harming the ecosystem seriously over the centuries. This and the early

protection by the Royal Forest Department saved most of the natural forests in the

area. Unfortunately illegal logging, fires started by poachers and local cattle owners

and the increasing need for more agricultural land present a threat to the forests.

Parts of the area had been selectively logged legally by a government-run enterprise

in the late 60’s and 70’s, but only touching the eastern part of the sanctuary, not the

core area.

Huay Kha Khaeng Wildlife Sanctuary is considered to be one of the last major gene

pools and reserves of natural forest and wildlife in Southeast Asia.

4.2 History of land use in Huay Kha Khaeng

During the last centuries the area was used for swidden agriculture by various ethnic

groups. Ancient burial grounds at various places in the sanctuary are a sign of their

existence and excavations have revealed agricultural tools (SANGVICHIAN, and

SUBHAVAN, 1981). During the 60’s and 70’s the area was partly under concession

to the Thai Plywood Logging Company. Valuable tree species were harvested,

mainly at the eastern side of the sanctuary. The concessions were terminated in the

mid 70’s and, as usual in Thailand, the local population and immigrants from the

north-eastern parts of Thailand used the area for hunting and gathering of Non-

Wood-Forest-Products and to collect timber for construction. Subsequently resin

(Dipterocarpus sp., Shorea sp.) was tapped and charcoal was made.


30

The tradition of using the area as grazing land for cattle is still a threat to the

sanctuary. Local farmers burn degraded land in the vicinity of the sanctuary and

eventually the fires reache the core area. One of those man-made fires in, possibly

triggered by the annual agricultural burning practice and supported by a very poor

rainy season, destroyed 5,600 ha of forests in the eastern part of Huay Kha Khaeng

in 1994 (THAILAND REMOTE SENSING CENTRE, 1994).

4.3 Research site

The area under consideration (the drainage basin of the Song Thang river) is a valley

covering about 5 by 10 km, fanning out north-east wards into the Central Plain (see

Figure 5). It is surrounded by two mountain ridges (up to 1,000 m.a.s.l.) running

parallel to the East and West and an appr. 4 km wide and about 500 m.a.s.l. ridge

represents the southern boundary. Altitudes in the valley range from 180 m.a.s.l. in

the north-east to about 300 m.a.s.l. in the South. The micro-topography of the valley

is characterised by small hills and depressions, creating a gently undulating

landscape.

Figure 5: Research area at Huay Kha Khaeng, at the Song Thang valley. View from the

southern ridge, with the bordering western ridge


31

Three forest-types were identified in the valley:

• Mixed Deciduous Forest,

• Dry Dipterocarp Forest

• Evergreen Forest.

The slopes surrounding the valley-basin are covered either by Mixed Deciduous

Forest or Dry Evergreen Forest and in some cases bamboo. Riparian Forest occupies

small areas or strips along rivers and - with increasing distance from the rivers -

mostly merges into Mixed Deciduous Forest.

In some cases the transition is very abrupt and Dry Dipterocarp Forest occurs

adjacent to Riparian Forest. Lower Mixed Deciduous Forest occupies the largest

proportion of the area under consideration, especially on the deeper and more fertile

soils. Teak is absent.

Dry Dipterocarp Forest occupies only small areas of the valley, mostly on the dry

bottom of slopes, where shallow lateritic soils occur.

4.4 The main forest types in the valley

Different forest types exist in Huay Kha Khaeng and its vicinity. The most dominant

are Deciduous Forests and Evergreen Forests. The first cover more than 50% of the

sanctuary with the two the sub types:

• Mixed Deciduous Forests (MDF)

• Dry Dipterocarp Forests (DDF)

They again cover large areas of the sanctuary and the buffer zone and are believed to

be the most intact and least disturbed deciduous forests in Thailand.

In particular, the existence of Dry Dipterocarp Forests at different stages of

degradation was important for this study. This was the main reason the valley in the

eastern part of Huay Kha Khaeng was chosen as the prime research area.


32

Both MDF and DDF are the most dominant forest types in the region and have a high

silvicultural potential for Southeast Asia. As they grow on soil suitable for

agriculture, large areas previously covered by them have been lost in the past. This

study will focus on the Dry Dipterocarp- and the Mixed Deciduous Forest, other

main forest types of Thailand are described in the Appendix to give a general

overview of the forest situation.

4.5 Geomorphology

During the Palaeozoic Period, Thailand was influenced by marine sedimentation.

The Precambrian gneiss’s, such as the quarzitic rocks of the Cambrian and

limestone’s of the Ordovician age, result from there. The soil types developed from

this parent material are the Chromic Luvisols (red brown earth) and the Acrisol (red-

yellow podzolic) (MOORMANN 1967).

The soils are usually poor and with a low pH. Along the river beds and wherever

areas are covered by floods during the rainy season, there are more fertile sediments

(NAKHASATIEN and STEWART-COX 1990). These yellow podsols are the most

dominant soil types existing in Thailand, covering 60% of the classified area

(RUNDEL, 1995).

4.6 Climate

The Western Forest Complex of Thailand, of which Huay Kha Khaeng is part of,

stretches along the Thai/Myanmar border and is greatly influenced by the monsoonal

climate. This climate can be characterised by 3 distinct seasons:

• the dry, cool season from November until January

• the dry and hot season from February until April

• and the warm and wet season between May and October

The average minimum and maximum daily temperature varies between 10° and 29°C

in the dry and cool season, 15° and 36°C during the dry and hot season and 20° and


33

33°C in the warm and wet season. The rainfall pattern can be divided into areas

considered to be dry, i.e. the south-eastern part of the sanctuary where the research

site is, and areas fully affected by monsoon. The latter areas can receive up to 4,000

mm of rain annually, while the dryer areas receive between 1,200 and 2,400 mm

annually. The climate is affected by rain fall pattern as roughly 80% of the annual

precipitation occurs during the rainy season. The rest of the year receives only 20%

with the so called “mango showers” in April and some cyclonic storms during the

dry and hot season.

Mean Monthly Precipitation (1980 - 1995)

Janu

ary

Febr

uary

Mar

ch

April

May

June

July

Augu

st

Septe

mbe

r

Octob

er

Nove

mbe

r

Dece

mbe

r

[mm]

0

30

60

90

120

150

180

210

240

270

300

Figure 6: Mean monthly precipitation at Huay Kha Khaeng (1980-95)

The high variability displayed in Figure 7of more than 1,000 mm between the very

dry year of 1982 (1,105 mm) and the very wet year of 1988 (2,181 mm) with

devastating floods in the south and north, is common in Thailand.


34

Annual Precipitation

1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995

[mm]

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

Mean Annual Precipitation (1494 mm)

Figure 7: Annual Precipitation at Huay Kha Khaeng, Thailand (1980-1995)

The mean annual precipitation of 1,494 mm in Huay Kha Khaeng might be

overestimated because of the very unusual amount of rainfall in 1981, 82 and 88.

Heavy thunderstorms, before, during and after the rainy season affect Thailand,

resulting in massive downpours overshort periods of time.

In November 1988 the Royal Thai Meteorological Department, Bangkok reported a

record 735 mm (448 on Nov. 21 and 287 mm on Nov. 22) during 2 days of heavy

rain, followed by floods. The deaths of more than 350 people and the related

destruction prompted the Thai Government to introduce the logging ban. Due to

administrative difficulties, no reliable data is available for 1996 and 1997. Rainfall

data was taken at a research station in Huay Kha Khaeng, close to the research plots.


35

These incidents, though usually not as heavy as in 1988, increase the total amount of

rainfall during a given year, but might not have an impact on plant growth in general.

The timing of rainfall and its overall distribution during the rainy season determines

the regeneration, establishment and development of the plant communities in the

area. A late start to the rainy season as in 1995, 96 and 97, combined with

unfavourable distribution of rainfall, even though the total amount of precipitation

was close to or even above average, could actually have a negative impact on plant

growth as opposed to more equal distribution during the whole rainy season with less

than the normal total.

.

Data assessment of structure and species composition in MDF and DDF

37

5 Data assessment of structure and species composition

in MDF and DDF

In the previous chapter reasons for the choice of research area and a background

history of land use and forest cover was given. The following chapter assesses

structure and species composition of the two forest types under consideration using

statistical analysis. The methods and statistics utilised for the assessment will be

explained, followed by the results of the analysis. The assessment and the results will

be summarised and discussed at the end of the chapter.

Floristic assessment of the MDF and DDF stands is essential for the next chapters

analysis of growth and yield.

5.1 Methods

5.1.1 Interpretation of aerial photographs

Interpretation of aerial photos can give an overview of the state of large areas of

forest and can help identify different forest types and levels of disturbance. The

overall aim of the aerial photo analysis was:

• To identify the different strata of relatively uniform stands in the dry deciduous

and mixed deciduous forests.

• After this first screening pre-defined DDF and MDF stands could be subdivided

into homogeneous stands, depending on age and state of degradation etc.

• Ground truthing served to define the areas used as starting points for a series of

temporary sample plots for the floristic inventory.


38

Aerial Photographs used:

Source: Royal Thai Army Survey Department, Bangkok, Thailand

Date of photo acquisition: December 94 and January 95

Film: Black and White

Photo overlap: min. 60% in flight line

min. 30% side lap

Size of aerial photos: 25.4 cm x 25.4 cm

Scale: 1 : 50,000

The differentiation of forest types was based on a visual interpretation of structure

and density, tree height, distribution and associated ground vegetation.

On the basis of a stereoscopic aerial photograph interpretation (SPD 300 and

AVIOPRET) of images of 1994 and 1995 (1: 50,000) and topographic maps of 1967

(1: 50,000), four different forest types have been identified and delineated within an

area of about 20 km2.

The intended analysis of the available aerial photos was hampered by their scale and

quality. As a result it was difficult to achieve a high resolution classification.

However, the analysis was able to identify the main topographic features of the area

(plains, undulating hills, steep slopes and ridges) and the different forest types

(disturbed and undisturbed DDF, MDF, bamboo forests and riparian forests).

Three areas which appeared to represent DDF and MDF, were pre-selected for

further studies. In the actual site selection for the later inventory, flat areas in the

centre of the valley under investigation were given preference. It might be argued

that these areas are not prime sites for forestry - they are more suited to agriculture -

but all over Southeast Asia, DDF and MDF cover vast areas similar to the research

area selected.


39

The selected areas appear representative of the forest types under investigation and

are sufficiently large in extent to minimise edge effects. Selecting areas on the flat

valley bottom has a number of advantages in a situation where little is known about

the forest. Most importantly, the effects of aspect and slope on the forest composition

are excluded.

5.1.2 Research site selection

Based on aerial photo analysis, reference points (kilometre-markers along the only

north-south road transecting the area) were marked and a series of transects running

East-West were selected and surveyed for ground truthing.

Every kilometre, transects were laid out and geo-referenced with the aid of the

Global Positioning System (GPS). Each line extended about 1.5 km to the East and

West of the road. Notes were taken on forest-type (based on indicator tree species)

and its extent, stand structure, site physiography and soils. Based on the above

information, three areas were selected, representing:

• the wide range of stand-types as found in dry dipterocarp forests (Baseline 1)

• a transition zone composed of both dry and mixed deciduous forest elements

(Baseline 2),

• and an area of mixed deciduous forest. (Baseline 3)

Site selection was also influenced by the fact that a series of long-term observation

plots was to remain after the study.

5.1.3 Placement of temporary plots

Along the baselines at 50 m intervals plots were laid out, alternating between the left

and the right of the central line. Baseline 1, representing dry dipterocarp stands,

contained 18 plots, Baseline 2 (Figure 8), a transition-zone between dry and mixed

deciduous forest contained 41 plots and Baseline 3, a mixed deciduous stand,


40

contained 17 plots. Sampling of the temporary plots consisted of three grouped sub-

plots (Figure 9). Sub-plots for the sampling of trees larger than 5 cm DBH were

circular, with a radius of 15 m (706 m2).

Plot size for this assessment was determined on the basis of previous works

(SUKWONG, 1974; KUTINTARA, 1975; BUNYAVECHEWIN, 1983, 1985, 1986)

and preliminary work (abundance estimates, species area curves) ensuring a

minimum of about 30 tree ≥ 5 cm DBH in each sample.

1 3 5 7 9 11 13 15 17 23 25 27 29 31 3319 21

Baseline 2

2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32

Roa

d

220

320

masl

DDF DDF/MDF DDF DDF/MDF MDF DDF

Transition Transition

0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 m

Figure 8 Outline of temporary plot design, representing Baseline 2

• In each 15 m radius plot, all trees and woody climbers larger than 5 cm DBH

were identified, DBH and crown intersection were recorded and its social position

was defined via crown assessment (after DAWKINS, 1958). Social position was

based on values from 1 to 5, mainly indicating the access to light of tree crowns.

For details on classification see LAMPRECHT (1990). The height of every fifth

tree was measured.

Samples of unknown species were taken and treated for later identification.

Diameters were measured at breast height to the nearest millimetre (1.30 m above

ground) with a diameter tape.


41

The DBH of trees that forked below

1.30 m in height was recorded for each

stem and later summarised into a total

basal area. Height was measured to the

nearest ½ metre with the help of a

Suunto height meter. To asses crown

width, four measurements (north, south,

east, west, to the nearest ½ m) were

taken on the ground from the centre of

the tree to the point of vertical crown

projection on the ground. Crown

intersection was defined as the height

of the stem at the onset of the first living branch of the continuous crown. Lower

branches were recorded separately.

• Saplings between 2 and 5 cm DBH were sampled in 10 x 10 (100 m2) sub-plots.

In these sapling plots, all trees, shrubs and woody climbers between 2 and 5 cm

DBH were identified and their height and DBH recorded.

• Seedlings and other woody plants smaller than 2 cm DBH were identified and

enumerated in 5 x 5 m (25 m2) sub-plots.

To avoid damage during sampling, seedlings were sampled first, then saplings and

finally trees. Sub-plots were located in the far (from the central transect line) right-

hand quadrant of each plot to minimise any damage from the marking of plot-

centres.

Further information gathered from each sample plot included a general site

description and information on soil and ground cover.

Figure 9: Temporary Plot

15 m

5 x 5 m[Regeneration]

10 x 10 m


42

5.2 Floristic assessment and forest type stratification

In the following assessment the main results from the inventory of structure and

composition will be presented. By using cluster (CL) and correspondence analysis

(CA) the main floristic characteristics of the Mixed Deciduous Forests – MDF – and

the Dry Dipterocarp Forests – DDF – could be assessed. A short introduction to the

statistical methods used will be given beforehand.

5.2.1 Statistical methods applied for the analysis

Classification, ordination and gradient analysis represent different though

complementary strategies to organising data. Direct gradient analysis arranges

species and community variables along recognisable environmental gradients.

In contrast, ordination (or indirect gradient analysis) as well as classification

organises community data according to the similarity or otherwise of community

characteristics (for example specific composition, species abundance, dominance)

without explicit knowledge of environmental factors, so leaving environmental

interpretation to a subsequent step (JONGMAN et al., 1987).

Ordination results in species and samples being arranged in a low-dimensional space

so that similar entities are grouped together and differing entities are separated.

Classification serves to group individual units (samples, species) and link them

hierarchically (GAUCH, 1982).

In contrast to uni- or bivariate statistical methods concerned with testing hypotheses,

multivariate statistical methods mostly serve to explore data and to find data-internal

structures from which hypotheses can subsequently be generated. Though weak when

dealing with only one or two variables (of known distribution), multivariate methods

are more powerful than classical statistical methods in dealing with large numbers of

attributes (including situations of non-Gaussian distribution). In this analysis two

statistical tools/methods have been used:


43

1. CLASSIFICATION

Classification is based on the assumption that floristically similar community-types

exist. Two main lines of classification are differentiated: The early, "subjective"

methods like the Zürich-Montpellier School of BRAUN-BLANQUET and the newer

numerical ("objective") methods. The terms subjective and objective must however

be treated with caution. All classification methods are subjective since they require

choices to be made at one point or another. Computerised classifications are

objective only insofar that they are repeatable within a given set of assumptions

(LONGMAN and JENIK, 1987).

Classification in the form of cluster analysis - CL - as applied in this study was

hierarchical-agglomerative. Individuals were added in accordance to their similarity

in an increasing hierarchy until the whole population was covered.

The expression of similarity or otherwise between pairs of quadrates is usually

expressed as their distance in mathematical space. Euclidean distance is the

geometric distance in multidimensional space and probably the most commonly

chosen type of distance. In this study squared Euclidean distance was applied. It

places progressively greater weight on objects that are further apart (KENT and

COKER, 1995). The fusion process of joining similar individuals into larger groups

is based on one of a number of iterative processes that compute between-group

linkage-distances.

An alternative is to use the analysis of variance to evaluate distances between

clusters. This so-called minimum variance clustering or WARD or error sums of

squares method attempts to minimise the Sum of Squares (SS) of any two

(hypothetical) clusters formed at each step. This method is regarded as very efficient

and was the basis of this analysis.

2. ORDINATION

Cluster analysis helps in aggregating samples of species or plots into groups.

However, besides group affiliation and linkage distance it provides little information

on the actual relationship of one cluster with another.


44

To obtain such information from the data it can be subjected to correspondence

analysis -CA -. The method was first applied by HILL (1973, 1974). Conceptually

related to weighted averaging (CURTIS and MCINTOSH, 1950, 1951), its

computation is similar to that of principal component analysis – PCA -

(GOODALL, 1954). Expressed in geometric terms, in a given multi-dimensional

data space the first step of a PCA consists of moving the centre of the co-ordinate

system to the data centroid (average of species). This is followed by rotating the co-

ordinate axis so as to capture as much variance as possible on the first axis. Much of

the remaining variance is then expressed on a second axis placed orthogonally over

the first and so on. One of the main shortcomings of PCA is that the underlying

model assumes that variable response (e.g. species abundance) to environmental

gradients is linear, though in most cases species response approximates a Gaussian

normal curve (GAUCH, 1982). Subsequently, the position of samples along derived

gradients is distorted into an involuted arch.

An alternative name for CA - reciprocal averaging - derives from the fact that the

species scores of CA are averages of the sample scores and reciprocally, the sample

scores of CA are averages of the species scores. As such the method is superior to

PCA in a number of ways. Although the results display another arch-effect, in CA

they can not be involute. It can handle more heterogeneous data and long community

gradients and it requires fewer computational resources (WILDI, 1995).

5.2.2 Assessment of the temporary plots

To assess structure and composition, data collected from all 76 temporary plots was

used. The methods of collection and the statistical analysis are outlined in chapter 4.

The analysis of the species composition in the MDF and DDF revealed (see Table 3)

a total of 186 tree and shrub species from 103 genera and 45 families in the three

generic diameter classes under investigation:

• 103 species were present in the so-called stand group (DBH ≥ 5 cm),


45

• 68 in the so-called sapling group (2-5 cm DBH) and

• 94 in the seedling group (< 2 cm DBH).

Table 3: Results of the floristic inventory

COLLECTIVE DBH-CLASS

≥ 5 2-5 < 2

Sample plot size (m2) 706 100 25

Total sample area (m2) 53721 7600 1900

Standing trees (live) 2895 701 6960 Stems/ha 539 922 36632 No. of species 103 68 94

Mean abundance/sample 38.09 10.01 91,57 S.D. abundance/sample 16.27 7.46 67.83

Abundance range/sample 8/81 1/26 12/355 Mean no. of species/sample 13 4 15

S.D. species per plot 5.14 2.26 6.08 Species range/sample 2 / 25 1 / 11 3 / 29

Species representing - 1 individual only (total,%)

14 (13.6) 17 (25.0) 6 (6.4)

Species representing - 2 individuals (total,%)

10 (9.7) 10 (14.7) 5 (5.3)


4 (3.9) 8 (10.3) 6 (6.4)


1 (1.0) 3 (4.4) 5 (5.3)

Species each contributing < 1% to the total (total,%)

79 (76.1) 46 (67.6) 69 (73.4)

In distribution terms, there were 40 species unique to the seedling and sapling group.

These did not occur in the larger diameter groups. Based on information provided by

SMITINAND (1990), seven species regenerate as potentially large trees, the rest

constitute understorey vegetation, shrubs and small climbers. Less than 0.4% remain

unidentified, either in vernacular or scientific terms. In total, 15 species could not be

properly identified and are known only by their vernacular name.


46

Of species identified:

• 179 minimum for mixed deciduous communities,

• 130 for mixed deciduous and evergreen formations

• 57 species in mixed as well as dry dipterocarp formations.

Seven species appear to be restricted to dry dipterocarp forests. As would be

expected, the number of individuals/ha increases with decreasing sampling diameter,

though actual numbers are highly variable. Similarly, with smaller sample diameter,

the number of species per sample plot increases and becomes more fluctuating. Both

abundance and species numbers reflect the heterogeneity of each sampled

population. Trees ≥ 5 cm DBH are floristically the most heterogeneous group.

Nearly 1/3 of species occur only once. A large proportion (83.6%) represents less

than 1% of the total while the five most common species contribute 33.8% (Table 4).

Table 4: Relative abundance (%) of the five most abundant species per diameter group and their presence in other groups

SPECIES DBH-Class ≥ 5 cm 2-5 cm < 2 cm

Shorea siamensis 11.6 1.7 3.4 Shorea obtusa 10.3 16 4.2 Schleichera oleosa 5.2 2.0 1.2 Stereospermum neuranthum 3.4 0.9 1 Croton oblongifolius 3.2 16 12.3 Hymenopyramidis brachiata. 3.6 11.6 2.5 Terminalia alata 2.1 4 0.5 Lannea coromandelica 3.2 3.7 0.4 Leguminosaceae spp.. 1.2 - 10 Papilionaceae spp.. - 0.3 5.4 Cratoxylum sp. 0.1 2.4 4.9 Terminalia nigrovenulosa 1.7 0.1 4.3

BOLD =% of top 5 species per DBH group

33.8 51.2 37.0


47

This is insignificant when compared to the diameter class 2-5 cm (51.2%).

Overall, individuals in this class appear under-represented (six plots were completely

void of trees), though this might be attributable to the sample area chosen being too

small. The seedling group is floristically more complex than the saplings studied, but

does not reach the levels of trees ≥ 5 cm DBH.

On the other hand, individual samples are highly heterogeneous. The seedling group

shows the highest mean number of species and standard deviation (15 ± 6.08) per

plot, as well as the highest number of species found in any sample (29). In smaller

diameter groups, understorey species, in particular Croton oblongifolius and different

climbers such as Hymenopyramidis brachiata and a species of the family

Leguminosaceae, begin to dominate at the expense of the otherwise dominant species

Shorea siamensis and Shorea obtusa and to a lesser degree Schleichera oleosa.

Species-area curves determining the sample plot size were created using data from

the 76 sample plots, following the method applied by ELLIOTT (1989) in similar

communities. Plots were selected at random from those available and newly

encountered species were added to the previously encountered species. The random

selection process was repeated 10 times and the mean figures were combined to

produce a smooth curve (Figure 10).


48

Number of plots surveyed5 10 15 20 25 30 35 40 45 50 55 60 65 70 75

Tot

al s

peci

es e

ncou

nter

ed

0102030405060708090

100110

Figure 10: Species curve over all samples (76 plots)

A non-linear estimate of the species area curve was based on the hyperbolic function:

)073.9(24.114

)(xx

xf+

=

The resulting R equalled 0.998, R2 exceeded 0.99. In other words, in an

undifferentiated survey of deciduous forest communities roughly half the samples

(equivalent to 2.68 ha) would account for 90% of the species found. However, it

should also be noted that the curve does not approach an upper maximum, i.e. ever

more species would be expected if the sample area was increased.

5.2.3 Resulting dominance-types

The cluster analysis of stand data reveals a continuum of community-types

characterised by two distinct dominance-types at both ends of the range (Figure 11).

Specific composition tapers from the xeric, DIPTEROCARPACEAE-dominated

stands to stands of mixed and more mesic composition. The following figures use a

species code.


49

Appendix 1 contains a complete list of species found and their respective 8 digit

species code. The first four letters of the genera and the first four of the species e.g.

Shorea obtura have been used for the code.

30

40

50

60

70

80

90

100

110

SH

OR

SIA

MS

HO

RO

BT

UT

ER

MC

OR

TLA

NN

CO

RO

TE

RM

CH

EB

TE

RM

ALA

TM

AM

MS

IAM

BU

CH

LATI

VIT

EX

1X

YLI

XY

LOS

TE

RN

EU

RP

TE

RM

AC

RT

ER

MN

IGR

LAG

EV

ILL

LAG

EC

ALY

VIT

EP

INN

DIO

SC

AS

TS

CH

LOLE

OD

ALB

CU

LTG

RE

WT

OM

ET

ER

MB

ELL

LEG

UM

IN1

BO

MB

AN

CE

SP

ON

PIN

NC

AS

SG

AR

RC

AS

SF

IST

SIN

DS

IAM

RA

ND

DA

SY

MIT

RH

IRS

BA

UH

MO

NT

DA

LBO

LIV

EU

GE

CU

MI

ME

ME

ED

UL

CA

NA

SU

BU

MIT

RC

AD

AA

NT

IDE

S1

ZIZ

YC

AM

BM

AR

KS

TIP

LAG

ET

OM

EH

AR

RP

ER

FH

YM

EB

RA

CC

RO

TOB

LOA

LAN

SA

LV

Figure 11: Dominance-types as derived from cluster analysis of the data DBH ≥ 5 cm (Ward method, after elimination of outlier plots and reduction of data to species with an absolute frequency > 8, linkage distance relative to maximum linkage distance)

On the xeric and dry end of the spectrum (left-hand side of the dendrogram) species

representing the Dry Dipterocarp Forests are dominant:

Shorea siamensis (SHORSIAM), S. obtusa (SHOROBTU), Terminalia corticosa

(TERMCORT), T. alata (TERMALAT), T. chebula (TERMCHEB), Buchanania

latifolia (BUCHLATI), Lannea coromandelica (LANNCORO) and Mammea

siamensis (MAMMSIAM).

The more mesic stands (right-hand side of the dendrogram) are characterised by:

Alangium salviifolium (ALANSALV), Croton oblongifolius (CROTOBLO),

Hymenopyramis brachiata (HYMEBRAC), Harrisonia perforata (HARRPERF),

Lagerstroemia tomentosa (LAGETOME), Markhamia stipulata (MARKSTIP) and

Zizyphus cambodiana (ZIZYCAMB).


50

The dendrogram shows a distinct separation of the xeric community-type from the

rest of the dendrogram, while the other, right-hand side of the dendrogram shows

signs of “chaining”. Although weakly pronounced it indicates an underlying pattern

among more mesic species.

Clustering the sample plots in a similar way helped to stratify the data into four sub-

types:

• Two in the xeric spectrum (type DDF), and

• two in the mesic, mixed spectrum (type MDF).

In Figure 12 the right-hand side represents xeric sites, the left-hand side mesic sites.

The main division falls between plots P 31 and P 32, sub-divisions run between P 50

and P 74 and between P 23 and P 41, respectively.

0

20

40

60

80

100

120

P60

P59

P58

P56

P54

P64

P53

P55

P65

P50

P74

P72

P71

P40

P39

P36

P48

P37

P34

P61

P57

P52

P51

P66

P63

P62

P49

P33

P43

P44

P35

P42

P32

P31

P30

P28

P73

P41

P38

P29

P45

P24

P70

P69

P76

P75

P26

P23

P21

P47

P19

P14

P13

P12

P16

P27

P15

P68

P20

P46

P18

P22

P17

P7

P25

P67

P6

P10

P8

P4

Figure 12: Group-structure of sample plots as derived from cluster analysis of the data

DBH ≥ 5 cm (Ward method, after elimination of outlier plots and reduction of data to species with an absolute frequency > 8, linkage distance relative to maximum linkage distance)

There are strong differences between the linkage distances at plot and species level

as well as at higher grouping levels. Species are joined later (at a much higher level)

than plots, an indication that species abundance and dominance pattern show

similarities between plots.


51

The correspondence analysis performed on the data confirms the observations

derived from the cluster analysis of species and plots.

The most xeric species are scattered on the left-hand side of the arch while the mesic

species favour the right (Figure 13). In-between are two groups, an intermediate

xeric group containing the two Shorea species (SHOROBTU, SHORSIAM) and an

intermediate mesic type, containing Pterocarpus macrocarpus (PTERMARC), Xylia

xylocarpa (XYLIXYLO) and some others. In clockwise direction they represent the

community-types DDF and MDF, as outlined previously.

ALANSALV

ANTIDES1BAUHMONT

BOMBANCE

BUCHLATI

CANASUBU

CASSFIST

CASSGARR

CROTOBLO

DALBCULT

DALBOLIV

DIOSCAST

EUGECUMI

GREWTOME

HARRPERF

HYMEBRAC

LAGECALY

LAGETOME

LAGEVILL

LANNCORO

LEGUMIN1

MAMMSIAM

MARKSTIP

MEMEEDUL

MITRCADA

MITRHIRS

PTERMACR

RANDDASY

SCHLOLEO

SHOROBTU

SHORSIAM

SINDSIAMSPONPINN

STERNEUR

TERMALAT

TERMBELL

TERMCHEB

TERMCORT

TERMNIGR

VITEPINN

VITEX1

XYLIXYLO

ZIZYCAMB

-1.5

-1.0

-0.5

0.0

0.5

1.0

-1.5 -1.0 -0.5 0.0 0.5 1.0

Figure 13: Position of individual species (horizontal axis = dimension 1, vertical axis

dimension 2); CA of basal-area data for trees ≥ 5 cm DBH


52

Similarly, the scatter of the sample plots as derived from the CA reflects the groups

as derived from the cluster analysis. From a quantitative perspective, axis (or

dimension) one explains 18.5% of the total inertia (chi-square value), axis two 9.58%

and axis three another 5.59%. The axes are orthogonal, that is to say independent

from each other. Considering the fact that the analysis generated 42 dimensions and

that sampling was un-stratified, the derived explanatory power of the axis must be

considered high.

5.2.4 Verification via correspondence analysis

As explained in the previous chapter, the analysis of temporary plots was a pre-

requisite for finding representative areas for permanent sample plots based on

species composition and stand density. It was necessary because of a lack of detailed

descriptions on how a dry dipterocarp- , resp. a mixed deciduous forest is defined.

The commonly used descriptions of the forest types of Mixed Deciduous Forests –

MDF - and Dry Dipterocarp Forests – DDF – take only species composition and

sometimes stand density into account ,and are not suitable for distinguishing between

DDF stands with higher or lower basal areas for example.

The floristic components are just one major factor in classifying a forest community

but to differentiate between, for example, a high quality and a low quality degraded

DDF stand, other factors have to be taken into account.

With a second correspondence analysis, the placement of permanent sample plots, -

used to assess growth and yield in the following chapter - in the corresponding forest

community type could be confirmed (Figure 14). This was combined with visual

interpretation of aerial photographs and on-site physical confirmation to support and

to verify the final placement.


53

Figure 14: Position of the 5 permanent plots in relation to all temporary plots

The graph above shows the placement of all sample plots, both temporary and

permanent. The numbers with a small cross represent the temporary plots ranging

from plot 1 to plot 76. The placement of 5 permanent plots, PP1-5 could be verified

and they are located with their corresponding forest type. On the left side of the arch

two Dry Dipterocarp plots, PP1 and PP2 are located, and on the right side the two

Mixed Deciduous plots, PP4 and PP5 can be seen. PP3, a plot in transition has been

placed in-between the DDF and MDF. The placement of the DDF plots in their

community type can be considered a better fit than the MDF plots due to the wider

variety of the MDF. To the right of the arch the MDF becomes more mesic and

eventually transforms into evergreen formations. Here the composition is structurally

and floristically different to the other samples, possibly due to past logging.

Considering the high proportion of dry evergreen species present in those plots and

their susceptibility to fire, it is most likely that this has also influenced the

composition. As a result no permanent plots are located in this part.

P2 P3

P4

P6 P7

P8

P9

P10

P11

P12 P13

P14

P15 P16

P17

P18

P19

P20 P21

P22

P23

P24

P25

P26

P27

P28

P29

P30

P31

P32

P33 P34 P35

P36

P37

P38 P39

P40

P41

P42

P43

P44

P45

P46 P47

P48

P49

P50

P51

P52

P53

P54

P55

P56

P57

P58 P59

P60

P61

P62 P63

P64 P65

P66

P67 P68

P69

P70

P71 P72

P73

P74

P75

P76

-1,0

-0,5

0,0

0,5

1,0

-1,5 -1,0 -0,5 0,0 0,5 1,0

PP-1

PP-3 PP-4

PP-5

PP-2

Assessment of research plots

55

6 Assessment of the research plots

In the previous chapter the general structure and composition of the Dry Dipterocarp

and the Mixed Deciduous Forests were analysed. This analysis served also in

establishing a set of permanent research plots within their corresponding forest type.

In the following chapter the methods and materials used to establish and assess the

research plots will be detailed, followed by the analysis of structure, growth and

yield.

For multi-temporal data collection, long-term experimental plots must be established.

For each forest type 2 plots were selected, one additional plot served as a transitional

plot between DDF and MDF, and finally a larger 2ha plot was established for the

subsequent growth prognosis in the next chapter.

The assessment of the 5 permanent plots was carried out over a 3 year period. For the

2ha plot 2 years of data are available. A code for each species was used in all graphs.

A summary of each code and respective scientific name and a basic yield table for all

plots is attached in Appendix 1.

For a better understanding a short introduction of the experimental plots will be

given:

• PP1 (DDF) : Poor stand with an open structure, heavily affected by fire and severe

logging in the past.

• PP2 (DDF) : Vital stand with sufficient regeneration. Stand is relatively unharmed

by fire, affected by logging, but in a recovering stage.

• PP3 (DDF/MDF) : Vigorous stand, species composition mainly belonging to the

Dry Dipterocarp Forests but influenced by MDF species as well, relatively

unharmed by fire, sufficient regeneration.

• PP4 (MDF) : Vital stand, sufficient regeneration across the stand, strongly

affected by previous logging.


56

• PP5 (MDF) : Relatively undisturbed stand with sufficient regeneration and

individuals across a wide DBH range.

• 2ha (MDF) : Least disturbed by human influence and fire, sufficient regeneration,

wide and continuous DBH range.

The following assessment will concentrate, whenever feasible, on the economically

most important species (main timber species), outlined in chapter 3.7.

6.1 Methods

6.1.1 Establishment of 5 permanent plots

The positions of the 5 permanent plots (PP1-5) were fixed against the existing

baseline (compare Figure 14) by taking the distance from point zero of the baseline

and the perpendicular distance of the plot centre from the baseline. The plot centres

were permanently marked with a 0.6 m, yellow iron peg. The three trees nearest the

peg were marked at breast height with yellow paint, facing the centre of the plot.

Sample size was determined on the basis of information from the temporary plots,

aiming for a minimum of 60 trees per diameter class (DBH class 5-15 cm, 15-25 cm,

etc.).

Three concentric, circular sub-plots were established (Figure 15):

• Trees and woody climbers were measured in a plot of 25 m radius (1,964 m2). All

trees received a unique metal number at eye level, facing the centre point. Trees

between 5 and 15 cm DBH were measured and labelled in an inner ring of 20 m

radius (1,257 m2), and correspondingly, in an outer ring between 20 and 25 m

(706 m2) all trees > 15 cm DBH were recorded. The outer ring served to avoid

edge effects in the plot and the data was later discarded. For each labelled

individual the distance from the plot centre and azimuth was recorded (0-360o) to

assess spatial distribution and for subsequent resampling.

Data collection followed the methods and tools applied in the temporary plots.


57

However, the DBH measuring point was marked with a small cut in the bark,

facing the plot centre. Tree height was measured for each specimen.

• Saplings between 2 and 5 cm DBH were measured within an inner circle of 10 m

radius.

• Regeneration and saplings

< 2 cm DBH were sampled in four

plots located 20 m from the centre,

along the cardinal axis. Plot size

was 2 m radius.

Further information gathered in each

permanent plot included a:

• general site description,

• topographical information,

• soil characteristics,

• light conditions and

• ground cover.

Crown intersection and crown radii (4 measurements, N-E-S-W, following the

compass bearings) were measured for every tree. Species were identified, their

heights recorded and particulars noted.

Stands were described with special reference to their apparent composition, their

vertical and horizontal structure, regeneration patterns and density.

6.1.2 Establishment of a 2 ha plot in the Mixed Deciduous Forest

During the analysis of the permanent plots it became apparent that more data on

mixed deciduous forest was needed to analyse the structure and dynamics. A

permanent plot of 100 x 200 m (2ha) (X-axis running along the previous Baseline 2,

Y-axis facing North) was set up in mixed deciduous forest at Baseline 2.

r1 = 10 m r2 = 20 m

r3 = 25 m

r4 = 2 m

Figure 15: Permanent plot design


58

The plot was divided into 32 sub-plots, each 25 x 25 m. All sub plots were marked

permanently in all 4 corners with 0.7 m, red iron pegs, driven about 0.6 m deep into

the ground. The inventory covered all of the previous data for trees ≥ 5 cm DBH,

including species, DBH, height, crown intersection, crown radii, crown cover, stem

form, and social position.

In addition, health, vigour, general appearance and any distinguishing marks

(wounds and damage resulting from fire, browsing, etc.) were recorded.

All trees were tagged with permanent metal labels at eye level and marked at 1.30 m

to indicate where the DBH measurement was taken.

In the 2ha plot regeneration was recorded in 4 strips, each 200 m long and 2 m wide,

running from East to West, parallel to the X-axis.

6.2 Auxiliary data collected in all permanent plots

6.2.1 Fish eye photographs

6.2.1.1 Methods

In all five permanent plots and in the 2ha plot, two series of fish eye photographs

were taken in 1995 and 1996, to record the light conditions present in the stands

under observation. Photos (Figure 16) were taken using a single lens reflex camera

fitted with fish eye lens. A tripod was set up at a height of 1.30 m with camera

attached, and pictures were taken either before sunrise, or after sunset to avoid the

glare of direct sun light. Each film (Kodak Agfa Ortho 25, Black and White) was

calibrated before development with a grey scale to ensure consistent results. All

pictures were then scanned (Polaroid Sprint Scan 35) to a resolution of 2025 dpi, and

the resulting images were stored on PC. The “tRAYci” programme, software for

analysing hemispherical images, was used for the final light calculations

(BRUNNER, 1998). In addition to the picture, tRAYci requires information on the


59

latitude and longitude of the sample area, duration of vegetation period, percentage

of diffuse radiationin canopy, plot size, and lens angle and orientation.

Figure 16: Hemispherical Photograph, taken in the Mixed Deciduous Forests, (Height of camera body is appr. 1.50 m above ground, radius appr. 20 m)

6.2.1.2 Results

The results confirm the correlation between the visual observations, derived from

using a prism for assessing the radii, and the crown cover results. PP1 and PP2

represent the open structure of the dry dipterocarp forests with the highest percentage

of light on the ground.

Figure 17 shows the available light in all permanent plots.


60

Amount of available light

0

10

20

30

40

50

60

PP-1 PP-2 PP-3 PP-4 PP-5 2ha-plot

Locat ion

Per

cen

t

Direct Sunlight %

Di f fuse %

Total %

Figure 17: Available amount of light in PP1-5 and the 2ha plot

PP3 contains the lowest readings of available light. This is because PP3 is in a phase

of pronounced regeneration, it represents a vigorous and little disturbed stand. PP4,

PP5 and the 2ha plot, appear with relatively closed canopies and little light on the

ground.

0 m 25 m 50 m 75 m 100 m 125 m 150 m 175 m 200 m

25 m

50 m

75 m

100 m

Figure 18: Light map of the 2 ha plot


61

Fish eye photographs were used later to create a detailed light map of the 2 ha plot.

In this map (Figure 18) the different shades of grey represent the amount of light

available in the plot. With the darker greys, the level of light decreases,

corresponding with the density of the canopy, and vice versa. Gaps, or areas only

partially covered by crowns, are represented by pale grey shades, for example the

area at points X = 75 m , Y = 25 m where the light map indicates a large gap in the

canopy. At Y = 12.5, 37.5, etc. transects were taken along the X- axis to map

regeneration for later analysis of the correlation between available light and

subsequent regeneration.

Unfortunately, this method produced no statistically significant correlation between

available light and the presence or otherwise of specific species in regeneration. This

can be traced back to the fact that only a few fish eye photographs were used to

calibrate the tRAYci software and they each represent the available light at just one

specific moment of time. Fish eye photographs should be taken at least monthly to

record available light more precisely. However, for general information on the

distribution of light (Figure 17) and to generate light maps as in Figure18, they are

very useful.

6.2.2 Increment assessment via borings

Data on tree increment is essential to growth prognosis. With the present logging ban

in place, prohibiting the felling of trees even for scientific experiment, boring

analysis was considered, as one option to reveal information on tree growth over

prolonged periods of time along with annual recordings of growth increment via

DBH measurement.

6.2.2.1 Methods

In April and May 1997, 165 bore cores of 11 main timber species were collected in

the DDF and MDF plots. In order to reflect development throughout the different

growth stages, the sample collection was divided into 3 DBH classes. For each


62

class, 5 samples were taken (Class 1 = 5 - 20, Class 2 = 20 - 35, Class 3 = > 35 cm

DBH).

Core samples of approximately 15 cm length and a diameter of 5 mm were collected

with a SUUNTO bore core extractor. These were sun-dried and stored in small

plastic tubes of 20 cm length and 5.5 mm diameter.

In August 1997 the bore cores were prepared using a high-precision moulding cutter.

The bore cores were then fixed on a plane and digital pictures where taken using a

high resolution video camera and a high resolution frame grabber graphic board.

Initial analysis took place at the Institute for Forest Growth and Yield Science

(Institut für Waldwachstum, Albert-Ludwigs-Universität, Freiburg) in Freiburg in

September 97. For details on the system see SPIECKER. With the ability to magnify

images up to 1000 times (see Figure 19), cell structure, crystal deposits and

intrusions could be visualised and were used for a first screening of the bore-cores.

Samples were analysed to check for distinct marks which could be correlated to

growth-ring-like structures.

Figure 19: Bore core sample of Shorea obtusa

6.2.2.2 Preliminary results

So far the analysis of the selected species revealed no dramatic results. As the

analysis and the involved processes showed, it is not possible to use bore core

samples alone for growth analysis.


63

Even with sophisticated high-tech equipment, the adaptation of existing computer

programs used in successful bore core analysis on temperate species was a tedious

and time consuming procedure. The calibration of the system needed many more

samples than expected before the results could be calculated. One main finding of the

analysis was that sample sets of bore cores from tropical trees should be used

together with tree disks to visualise similarities in structure and colour, allowing for

improved analysis later. Chemical and biological treatments can also be used to

enhance the contrast between cells.

6.2.3 Soil Survey

In November 1996, soil samples were collected in all the permanent plots. In each

plot, 50 soil samples were collected at different depths (0-5 cm, 5-20 cm, 20-40 cm

and 40-60 cm), thus each soil sample consisted of 4 sub-samples. Soil pits were dug

manually and the individual samples collected in plastic bags. The physical and

chemical properties of the samples were analysed by the Land Development

Department in Bangkok.

Analysis of the samples revealed distinct differences only in respect to the organic

matter content and therefore soil moisture content in the top layer (0-5 cm). The

organic matter in the Mixed Deciduous plots PP4, PP5 and the 2ha plot was nearly

twice as high as in the Dry Dipterocarp plots. In the layers from 5 to 60 cm the

analysis of the organic matter content revealed no distinct differences between the

two forest types.

Soil texture was analysed and the research plots could be grouped into SL (sandy

loam) and SCL (sandy clayey loam), again with no distinct differences.


64

6.3 Analysis of the permanent plots

6.3.1 Species composition and dominance

Species composition and distribution across all plots of both community types can

not be called homogeneous, particularly species with low frequency levels. Some,

such as Sindora siamensis and Terminalia spp. occur in small numbers in all 3 DDF-

plots (Figure 20), though never more than a few individuals/ha.

As explained in chapter 4, the total number of individuals/ha present in the DDF is

higher than in the MDF, although only a few species occur in high numbers/ha.

Species with high abundance are distributed relatively uniformly across the two

forest types, while the total number of occurrences varies across the plots. This can

be seen with Shorea siamensis and Shorea obtusa, both considered true and

dominant DDF species, which occur consistently at high percentages (Shorea obtusa:

PP1 39%, PP2 31% and PP3 11%; Shorea siamensis PP1 5%, PP2 20% and PP3 34%)

in each DDF plot.

The combination of those 3 plots can be seen as representative for DDF stands in

Thailand.

• PP1 is the most degraded one with the lowest potential.

• PP2 is in a stage of vigorous regeneration and the one with highest numbers of

individuals.

• PP3 is in a stage of transformation with more species of the MDF invading

(Schleichera oleosa, Vitex spp., Dalbergia spp) because of a low frequency of fire.

The higher total number of individuals in PP2 and PP3, compared to PP1 can be

linked to the higher potential of those two sites and to lower fire frequency. Most of

the individuals in PP1 have fire scars on the bark up to 3 to 4 m high, compared to

PP2 and PP3. It is therefore the most degraded and most fire susceptible plot with low

potential and subsequently less individuals/ha than the other plots.


65

PP1

[Number/ha]0 50 100 150 200 250 300 350

SHOROBTUSTERNEURANACOCCI

LANNCOROMAMMSIAMSHORSIAMRANDDASYTERMALATSINDSIAMDIOSCASTMITRHIRS

TERMCHEBSCHLOLEOTERMCORT

VITEPINNBAUHMONTCASSGARRMORICORE

DILLENI1

PP2

[Number/ha]0 50 100 150 200 250 300 350

SHOROBTUSHORSIAMLANNCOROSCHLOLEOHALDCORD

VITEX1XYLIXYLO

TERMCORTVITEPINN

RANDDASYGREWTOME

PHOEPANIDALBCULT

PTERMACRSTERNEURTERMGLAUBAUHMONTHYMEEXCE

SINDSIAMCANASUBUGMELINA2WALSVILLGMELINA1

PP3

[Number/ha]0 50 100 150 200 250 300 350

SHORSIAMSHOROBTUSCHLOLEOLANNCORO

GREWTOMEDALBCULT

VITEPINNVITEX1

VITELIMOTERMCORT

STERVILLVITEX2

CHUKVELURANDDASYDIOSCAST

HALDCORDSPONPINN

BOMBANCESINDSIAM

CANASUBUPHOEPANI

TERMGLAUDALBCAND

ANTIDES1PAVETOME

Figure 20: Species distribution in the DDF- plots PP1-3 (for the species code compare Appendix 1)

Shorea siamensis has a wider amplitude than Shorea obtusa, occurring in all of MDF

plots with the exception of the 2ha plot (Figure 21).

The occurrence of Shorea obtusa in the 2ha plot can be attributed to its very dry and

open site and is not representative for this MDF area. Schleichera oleosa, Randia

dasicarpa and Lannea coromandelica are, on the other hand, always present in both

forest types at between 1% and 22%.

In MDF the dominance of species is different to the DDF. It is of a complex

composition with no particular species dominating.


66

As explained in chapter 4, more species/ha are present and with more individuals per

species in the MDF. Tree species dominating here are Schleichera oleosa, Vitex spp.,

Terminalia spp., Lagerstroemia calyculata and Dalbergia spp. As can be seen in the

2ha plot, the larger the area sampled, the more species appear with one or two

individuals, supporting the results in chapter 4. The dominant tree species can be

assessed with smaller sample areas such as PP1-5, but this is to the detriment of

species occurring only once or twice per ha such as Afzelia xylocarpa.

Approximately 180 species were found in both community types. Only some of them

were as dominant as the Shorea spp. in the DDF: the difficulty of identifying

dominant species in the MDF supports the hypothesis that DDF and MDF are highly

related community types. Frequent fires in DDF stands might be one of the main

limiting factors, together with changes in soil characteristics, in the establishment of

a more mesic regeneration and the transformation or shift from DDF into MDF and

vice versa.

As explained before, regeneration (individuals < 5 cm DBH) in both community

types is not always represented in the upper canopy. This phenomenon indicates a

shift from xeric to mesic environment and is related to fire frequency and level of

disturbance.

6.3.2 Natural regeneration and its dynamics in the permanent plots

During the observation period, a total of 1050 seedlings and 324 shrubs were

recorded (66 tree and 12 shrub and climber species). The most dominant tree species

were Shorea obtusa and Terminalia nigrovenulosa. In 1994, they represented 10.0%

and 18.9% of the total population, respectively. In 1997, they were 15.4% and

24.4%. In contrast, the proportion of the third most common species, Shorea

siamensis,decreased from 9.2% to 6.0%. Important shrubs include an Antidesma

species (vernacular: Maeng-mao-yai), a Mallotus species (vernacular: Prao-noi), and

Ochna integerrima. In 1997 these represented 8.3, 4.9 and 3.9% of total abundance,

respectively. Overall, the first ten species constitute 72.6% of total abundance.


67

PP4

[Number/ha]0 20 40 60 80 100 120

SCHLOLEOVITEPINN

TERMNIGRMILILINE

DIOSCASTDALBOLIV

LANNCOROXYLIXYLO

DALBCULTSPONPINN

VITELIMOSHORSIAMHALDCORDRANDDASYSTERNEURTERMGLAUBAUHMONTHYMEEXCELAGECALY

STERVILLVITEX2

CASSGARRUNIDFIN

COMBPROCCROTOBLO

MILLLEUCCASEGREW

PP5

[Number/ha]0 20 40 60 80 100 120

TERMNIGRLAGEVILLVITEPINN

SCHLOLEOLANNCORODALBCULT

HALDCORDDIOSCAST

SHORSIAMRANDDASYTERMCORTPTERMACRMARKSTIPSPONPINNSTERNEURLAGECALYMITRHIRS

GARUPINNZIZYCAMBGMELINA3

2ha

[Number/ha]

0 20 40 60 80 100 120

LAGECALYTERMNIGR

VITELIMOSCHLOLEOWALSVILL

STERPERSXYLIXYLOUNIDENT1MILLBRAN

TERMCORTVITEPINNSINDSIAM

DYOSTRANANOGACUMCASSGARRHALDCORDLAGELOUDLANNCOROHYMEEXCEPTERMACRSPONPINN

TERMGLAUVITEX2

BUTEMONOLEPITETRUNIDENT9DIOSCAST

STERNEURSTERVILL

COMBPUNCALBIODOR

BOMBANCECASEGREW

CORDIA2GARUPINNANTISOOTMARKSTIPALANSALV

APORFICICASSFIST

DALBCANDLEPIRUBIMILILINE

RANDDASYALBILEBB

ANACOCCIBERRMOLL

DALBOLIVGARDENI3

MORICORESHOROBTUAFZEXYLOCLAUSEN1CLAUSEN2CORDDICH

CORDIA1CORDIA3

CRATFORMDENDROL1DENDROL2DENDROL3

GREWTOMEMEMEGEDD

MITRHIRSNAUCORIE

PARALONGUNIDENT3UNIDENT8UNIDENTX

Figure 21: Species distribution in the MDF- plots PP4 + 5 and the 2ha plot


68

With respect to the behaviour of individual species, there are no “general mast

years”. After the areas last fire in 1993, 1994 was unremarkable. In 1995 seeds were

plentiful and germination rates good. Consequently, seedling numbers increased

strongly in the following growing season. In 1996 overall population in the ten

samples more than doubled, however, this was concentrated in the Shorea obtusa

population (50.9% of total increase) and Terminalia nigrovenulosa (21.7% of total

increase). During the ‘96-97 dry season, mortality in the ranks of 1996 “recruits” was

high (a 25.5% decrease). Nearly 60% of mortality was among S. obtusa, slightly

more than 17% occurred in T. nigrovenulosa. In other words, though turnover of S.

obtusa is high, it is decreasing in its relative proportion, while T. nigrovenulosa is

increasing.

6.3.3 Distribution of individuals with respect to Social Position

In all permanent plots the Social Position of each tree (≥ 5 cm DBH) was recorded.

The assessment of social position was based on Dawkins’ (1958) crown

classification with Social Position:

5: Crown in full overhead and lateral light.

4: Crown in full overhead light, lateral shade.

3: Crown partially exposed to overhead light, lateral shade.

2: Crown without overhead light, partially shaded.

1: Crown shaded on all sides, no direct light.

Social Position 1, representing the understorey plants with virtually no access to

direct sun light is strongest in PP2, PP3 and PP4 (Figure 22) comprising more than

40% of each plot.

The 2ha plot has the lowest readings at 12%. Social Position 2, (trees with access to

some lateral light) is quite evenly distributed across the plots. Social Position 3 is

more strongly represented in the DDF plots (±33%), than in the MDF plots PP4

(22%) and PP5 (13%), however in the 2ha plot readings are high at more than 36%.


69

Due to the open, mostly twin layered stand structure of the DDF plots, few trees can

be clearly regarded as emergent or dominant(Social Position 5). This results in small

numbers represented in this group. Co-dominant trees (Social Position 4) show the

highest Social Position.

In the MDF plots with a 3 layered structure Social Position 4 lies between 20 and

31%. Social position 5 is best represented in PP5 with nearly 20% and shows weakest

in the 2 ha plot.

Considering the over all pattern it can be seen that the DDF plots have higher

percentages in the lower three Social Positions, counting for 60 to 70% of the total.

The upper layers, Positions 4 and 5 count for 20 to 30% with most in the co-

dominant layer. In the MDF plots between 30 and 50% of the individuals are

represented in classes 1 and 2. The rest are evenly distributed over Social Positions 3

and 4 and with naturally decreasing frequency in the dominant Social Position 5.

Here PP5 has the highest number of individuals in the dominant group with close to

20%, compared with PP1 at only 1%.

Distribution of Social Positions per plot

PP-1 (

DDF)

PP-2 (

DDF)

PP-3 (

DDF/M

DF)

PP-4 (

MDF)

PP-5 (

MDF)

2ha (M

DF)

Dis

trib

utio

n [%

]

0

20

40

60

80

100

Soc Pos 1 Soc Pos 2 Soc Pos 3 Soc Pos 4 Soc Pos 5

Figure 22: Distribution of all individuals across the Social Position


70

In DDF plots (PP1-3), Shorea obtusa and Shorea siamensis dominate in most of the 5

layers (Figure 23).

Social Posit ion

1 2 3 4 5

Nu

mb

er o

f In

div

idu

als

0

1 0

2 0

3 0

4 0

5 0Shorea siamensis

Shorea obtusa

Figure 23: Distribution of main DDF species across the Social Positions

The main species appear in high percentages in Social Positions 1, 3, and 4, but are

suspiciously lacking in Social Position 2. This could be related to strong bush fires at

the end of the 1980’s, probably halting regeneration at that time.

Shorea siamensis is well represented in Social Position 5, where Shorea obtusa

counts for only 1%. Other species such as Schleichera oleosa and Sterculia spp.

occur in Social Position 1, 2 and 3 in the DDF plots, but are not present in the upper

layer. Sindora siamensis and Terminalia spp. can only be found in Social Position 3

in all the DDF plots. Most other species occur across all Social Positions but only in

very small numbers.

In the MDF plots (PP4-5, 2ha plot) the distribution across the Social Positions is far

more diverse. Up to 40 species are well represented across all classes with

Lagerstroemia calyculata and Terminalia nigrovenulosa dominating the upper layers

4 and 5. They are dominant in the the upper canopy, along with Schleichera oleosa,

Walsura villosa, Xylia xylocarpa, Terminalia corticosa, Anogeissus acuminata,


71

Pterocarpus macrocarpus and Spondias pinata. The latter species is present in the

upper layer but only in small numbers and often lacks effective regeneration in the

lower Social Positions. 64% of all species occur with more than 2 individuals/ha

across two Social Position classes, 36% only one. Of the latter group 27%

(respectively 10% of the total) occur at more than 2 individuals/ha and 73%

(respectively 26% of the total) with one individual/ha.

Lannea coromandelica, Schleichera oleosa, Vitex pinnata and Stereospermum

neuranthum are species common in all layers and across all DDF and MDF plots,

indicating their wide amplitude and high adaptative ability.

6.3.4 Diameter distribution

For the graphs in Figure 24, the measured diameters were grouped in DBH classes of

5 cm range. The 3 graphs on the left display the DDF plots, the ones on the right the

MDF plots.

The total number of individuals in the lowest DBH-ranges in the DDF plots is two or

three times greater than the MDF plots. PP2 has the most with appr. 70% (see

Table 5) of its total extent represented at between 5-15 cm. The distribution within

the DDF plots follows a typical distribution pattern, with high figures in the lower

DBH classes decreasing towards the bigger DBH ranges. All of the DDF plots close

the range of diameter distribution in the DBH class 40-45.

No trees of bigger dimensions can be found in those plots, and there are no stumps or

trees left on the ground to give an indication that individuals with larger diameters

have been found in that community type. Commercial exploitation and illegal

logging in the area in the 1970’s could be a reason for the lack of large trees.

(personal communication with local foresters indicate that bigger trees were present

in the area before.)


72

PP1

5-10

10-15

15-20

20-25

25-30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

0

50

100

150

200

250

300

350

400

PP2

5-10

10-15

15-20

20-25

25-30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

0

50

100

150

200

250

300

350

400

PP3

5-10

10-15

15-20

20-25

25-30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

0

50

100

150

200

250

300

350

400

PP4

5-10

10-15

15-20

20-25

25-30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

0

20

40

60

80

160

PP5

5-10

10-15

15-20

20-25

25-30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

0

20

40

60

80

100

2ha

5-10

10-15

15-20

20-25

25-30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

0102030405060708090

100

DDF MDF

Figure 24: DBH Distribution across all DBH classes (note the different axes scales)

PP4 has the highest readings between 5-10 cm of all MDF plots with 33% of all

specimens represented here, but displays substantial gaps in more than one DBH

class, visible in the groups between 25 and 35 cm. Numbers are completely lacking

in the 40 to 50 cm range. The anticipated left-skewed appearance as seen in the DDF

plots is not apparent, they appear disproportionate and scattered.


73

Table 5: Distribution of all individuals across the DBH-classes, represented as %/plot

DDF DDF/MDF MDF

DBH-Class [cm]

PP1 PP2 PP3 PP4 PP5 2ha

5-10 44 32 39 33 23 18 10-15 20 38 26 15 12 15 15-20 13 15 10 12 15 14

20-25 7 6 9 15 17 13 25-30 8 3 5 2 8 11 30-35 5 3 3 5 10 7 35-40 2 2 6 13 2 7

40-45 1 2 2 5 45-50 2 4 50-55 2 2 2

55-60 2 4 1 60-65 2 1 65-70 2 1 70-75 2 1

75-80 1

Total [%] 100 100 100 100 100 100

The 2ha plot shows a relatively even distribution, indicating the least impact from

biotic and anthropogenic factors. In the 2ha plot the highest class (75-85 cm) is

represented, but substantial numbers in the lowest DBH-class are absent. This is

probably attributable to a fire incident 4 years prior to the time of the first data

collection.

Considering the relatively slow growth of the DDF and MDF and tracing the

incidents back over time suggests this might be a result of powerful and frequent

forest fires in the 70’s that destroyed most of the regeneration and medium size trees

in this area. The lack of significant numbers in the higher classes in PP4 and PP5,

where similar distribution patterns to the 2ha plot would be expected, can be

attributable to the same causes as in the DDF plots.


74

In DDF plots when compared to the MDF plots the differences in diameter

distribution become clear. In general the DDF plots display high numbers in the

lower DBH range, this rapidly decreases towards a DBH of 40 – 45 cm, and larger

diameters are totally lacking. In the MDF plots, if there is no negative influence as in

PP4 and PP5, the distribution is smooth, with a much wider range, up to 75-80 cm

DBH.

6.3.5 Basal area and increment

Basal area (b.a.) in the permanent plots was determined by computing annual DBH

measurements. For the PP1-5 the measurements (≥ 5 cm DBH) started in November

1995 and for the 2ha plot in 1996. Yearly measurements were taken and the results

displayed in Table 6.

Table 6: Development of the Basal Area from 1995 to 1997, (figures are rounded)

BASAL AREA DDF DDF/MDF MDF

PP1 PP2 PP3 PP4 PP5 2ha

1995 [m2/ha] 15.4 18.3 21.8 20.4 25.4 n.a.

1996 [m2/ha] Increase to 95 [%]

15.8 (+2.4)

19.2 (+5.0)

23.0 (+5.5)

21.4 (+5.1)

26.1 (+2.8)

23.1 (n.a.)

1997 [m2/ha] Increase to 96 [%]

16.0 (+1.6)

19.6 (+2.0)

23.6 (+2.5)

21.8 (+2.0)

26.5 (+ 1.5)

23.6 (+1.9)

Individuals/ha (>5cm DBH)

700 1,003 939 477 414 386

The DDF plots PP1 and PP2 have the lowest b.a. of all experimental plots. They also

show the variability in basal area typical of DDF forests. The individuals in PP2

make up appr. 3 m2 greater b.a., probably attributable to its vital regeneration with

high numbers of individuals in the lower DBH. This is also shown with the shortest

diameter range by highest number of individuals (compare Figure 24).


75

PP3, considered to be a DDF plot in transition to MDF, as explained above, displays

substantially higher b.a.

The MDF plot PP4 lies in the medium range, even lower compared to PP3. PP5 and

the 2ha plot displays the highest b.a. Looking at the increase in b.a. over time shows

modest differences in the percentages between the two forest communities. PP1

shows the least increase, attributable to the poor stand. PP2, PP3, and PP4 show an

increase of more than 5% in the year 1996 probably due to a long and satisfactory

rainy season. Again PP3 shows the highest figures, indicating a vital stand and its

state of transition.

In 1997 these plots again showed a higher increase in comparison with the other

plots, but generally not as high as the year before.

Information from the Bangkok Meteorological Dept. and the staff of the sanctuary

confirmed that 1997 was considered a very dry year with a late onset to a shorter

than normal rainy season. The low increase in total could not be correlated with

climate data as for the years 96 and 97 there is no data available.

PP5 has the highest b.a. of all with more than 25 m2/ha, but the average increase was

slightly lower in comparison with the other plots.

For the 2ha plot only one year of increment data was available which showed the

percentage of b.a. increase during that year to be similar to the other MDF plots.

Taking into account the number of individuals per plot, DDF holds more than twice

as many as the MDF with PP1 as the exception. The 2ha plot has the second highest

b.a. with the least number of individuals/ha and the largest diameter range. Tree

diameters extend up to 43 cm in the DDF plots and are much greater in the MDF.

In general the tree individuals of the DDF are limited in growth, where the MDF

sites support better growth.


76

6.3.6 Volume

The figures for the “solid volume over bark” are displayed in Table 7. Volume was

assessed after the first measurement of the tree heights. The margin for error in

assessing annual height increment can be regarded as very high, the permanent plots

were therefore measured only once. As no functions for volume assessment are

available at present, the Fagus sylvatica form-factor-function of the Chair of Forest

Growth and Yield, University of München, was utilised.

Table 7: Volume (solid volume over bark) in the permanent plots

VOLUME DDF DDF/MDF MDF

PP1 PP2 PP3 PP4 PP5 2 ha

1996 [m3/ha] 95 130 180 203 285 239

Individuals/ha (>5cm DBH) 700 1003 939 477 414 386

PP1 and PP2 have least volume, PP5 holds the most. Comparing PP1 and PP5 reveals a

figure exactly 3 times higher than PP5. PP4 is at the lower threshold of the MDF plots

and the 2ha plot fits in between with 239 m3/ha. In general the higher volume and

therefore potential of the MDF stands is clearly seen.

6.3.7 Crown characteristics and crown projection area

Figure 25 displays the crown area of all individuals in the research plots. The crown

maps represent the 4 crown radii.

The individual crowns show an irregular pattern with visible gaps across all plots. A

first visual assessment reveals distinct differences in crown size between the species

in the DDF and the MDF plots.

The DDF plots generally contain more individuals with smaller crowns. More than

50% have crown projection areas smaller than 10 m2. Roughly 40% are represented


77

between 10 and 60 m2. The maximum crown area in the DDF plots is reached at 120

m2, but few individuals develop to this extent.

Looking at the crown projections, the openness of PP1 is apparent, compared to the

other plots, this is also shown by the availability of light.

PP2 and PP3 contain more individuals in total/plot, but the distribution across the

crown projection range follows the pattern described above. The 2 storey structure of

the DDF means that individuals in the first layer have more access to light compared

to the MDF where 3 storeys are responsible for less light being available on the

ground.

The maximum crown projection areas of individuals in the MDF plots average 180

m2, with few individuals reaching as much as 400 m2 in the 2ha plot. Those

individuals count for less than 4%. Distribution across the range follows a more

regular pattern with roughly 25% of individuals having crown projection areas of up

to 10 m2 and 20% up to 20 m2.Crown dimensions of between 20 and 30 m2 represent

roughly 10%, Those between 30 and 40 m2 comprise 12%. With increasing crown

dimensions the number of individuals declines sharply but steadily. In the MDF plots

the individual crown projection areas are distributed across a wider range than in the

DDF.

The crown projection of the 2ha plot shows large gaps with virtually no crown cover.

Those gaps result from the recent fall of individual trees (> 25 m height) with large

crowns. The boles of those trees are still on the ground and fit with the shape of the

gap.

Regeneration < 5 cm DBH covers most of those areas, but is not displayed on the

crown map.


78

PP1 PP2 PP3

PP4 PP5

2ha Plot

0 10 20 m 0 10 20 m

0 10 20 m0 10 20 m 0 10 20 m

0 10 20 m

Figure 25: Crown maps of all plots representing the real crown radii


79

6.4 Selection of potential crop trees

6.4.1 Methods

In all permanent plots, including the 2ha-plot, potential crop trees – PCT’s - were

selected, dependent on species, stem quality, size and social position. Care was taken

to select individuals of high timber quality, in all growth stages if at all possible, in

order to maintain sufficient stock and regeneration in the future. Single tree selection

was given the highest priority to allow development with the least competition. In

special cases, where two or more individuals of high value and quality were found

together, they were selected as a group.

During this process not only trees with an economic potential were recorded, but also

their direct competitors and others of low quality and value were marked. The

competitors were defined as individuals with crowns directly competing with the

PCT’s for available light, or impeding their development by physically suppressing

their growth for example.

Individuals with poor stem quality or other negative traits were designated low

quality trees, to be removed or killed during any anticipated future liberation .

In Figure 26 the distribution of potential crop trees in one selected plot (2ha) is

shown.


80

0 m

20 m

40 m

60 m

80 m

100 m

0 m 20 m 40 m 60 m 80 m 100 m 120 m 140 m 160 m 180 m 200 m

Potential Crop Tree - PCT

Competitors and undesirable individuals

Remaining collective

Figure 26: All individuals of the 2ha plotted by their X and Y coordinate with appr. 130 potential crop trees across the whole stand.

The PCT’s display a generally uneven distribution across all plots, as can be seen in

the 2ha plot described here. Figure 27 shows the distribution of PCT’s in their

corresponding diameter class, across all plots.


81

PP1

DBH-Class

5-15

15-25

25-35

35-45

45-55

55-65

65-75

Ste

m N

umbe

r pe

r ha

0

50

100

150

200

450

500PP1-PCT PP1-Others

PP2

DBH-Class

5-15

15-25

25-35

35-45

45-55

55-65

65-75

Ste

m N

um

ber

per

ha

0

50

100

150

200

700


PP3

DBH-Class

5-15

15-25

25-35

35-45

45-55

55-65

65-75

Ste

m N

umbe

r pe

r ha

0

50

100

150

200

600


PP4

DBH-Class

5-15

15-25

25-35

35-45

45-55

55-65

65-75

Ste

m N

um

ber

per

ha

0

50

100

200


PP5

DBH Class

5-15

15-25

25-35

35-45

45-55

55-65

65-75

Ste

m N

umbe

r pe

r ha

0

50

100

150


2ha

DBH-Class

5-15

15-25

25-35

35-45

45-55

55-65

65-75

75-85

Ste

m N

umbe

r pe

r ha

0

50

100

150

2002ha-PCT 2ha-Others

DDF MDF

Figure 27: Distribution of Potential Crop Trees-PCT’s across the DBH range (note the different scales of the Y- axis)


82

The single trees and small groups of PCT’s are scattered, leaving open spaces with

no PCT’s. In most cases the crown projection area of potential crop trees and others

will cover these areas, but large openings exist in all plots with no PCT coverage.

Across the DDF plots between 50 and 135 individuals/ha were selected as potential

crop trees and in the MDF stands, coincidentally, there were always 64

individuals/ha that fit the qualifications set above.

In DDF plots the occurrence of PCT’s follows no regular pattern of distribution. Few

individuals qualify in the lower DBH classes, except in PP3. When comparing the

medium diameter classes between 15 and 35 cm, PP1 and PP2 hold substantially

greater numbers of PCT’s than PP3. In PP2 all individuals in the 35-45 cm range

qualify as PCT’s.

The MDF stands hold less potential crop trees but their distribution is more regular.

Few individuals qualified in the lower diameter classes, medium sized trees between

15 and 55 cm are fairly evenly distributed but occur infrequently in the larger

diameter classes and here only in the 2ha plot.

When looking at the distribution of the PCT’s across the Social Position, between 70

and 80% of the potential crop trees can be found co-dominant and dominant in the

higher positions (Social Position 4 and 5).

6.4.2 Basal area of the potential crop trees

Basal area of the PCT’s is displayed in Table 8, and compared with the b.a. of all

individuals in the respective plots.


83

Table 8: Basal area and percentage of individuals represented as potential crop trees,

DDF DDF/MDF MDF

Basal area: (% of total b.a.) PP1 PP2 PP3 PP4 PP5 2 ha

PCT’s 16 34 23 17 22 16

Proportion of: (% of the total collective)

PCT’s 8 13 10 13 16 17

Competitors 2 7 8 10 4 6

Undesirable trees 31 11 16 27 31 10

Indifferent 59 69 65 50 50 67

In both forest types the PCT’s are responsible for between 16 and 23% of the total

b.a., with the exception of PP2 with substantially higher figures. The actual number

of potential crop trees in comparison with total stem number is generally lower,

again with the extreme in PP2, where only 13% of individuals account for 34% of

the total b.a. of the plot, due to the vital regeneration stage of this plot. In the 2ha plot

the percentage is fairly balanced.

Competition is highest in PP3 and PP4 and extremely low in PP1, due to the open

nature of the latter.

The percentage of individuals/ha of low quality is highest in PP1 and PP4. For all

other plots they account for 11 to 27% of all individuals.

6.5 Discussion

6.5.1 Permanent plots and their characteristics

Long-term assessment of growth and yield can only be guaranteed with the

establishment of permanent research plots. They are a pre-requisite if one hopes to

gain reliable information. A series of permanent plots was set-up in the two forest

stand under consideration. A discussion about the assessment follows.


84

6.5.2 Selection and establishment of permanent plots

The addition of permanent plots supplementary to the correspondence analysis of the

temporary plots showed their positions relative to the co-ordinates created by

analysis. It also provided information on the representative qualities of the permanent

plots with respect to identified community types.

Permanent plots were deliberately selected to represent typical MDF and DDF stands

with little disturbance. The most mesic group identified by the initial correspondence

analysis was not covered by permanent plots because of the high proportion of dry

evergreen species present and the level of disturbance apparent.

6.5.3 Structure and species composition of selected permanent plots

Regarding species composition and their spatial distribution, major differences are

obvious:

The DDF plots are dominated by Shorea obtusa and S. siamensis.. The remaining

species occur only in small numbers. Exceptions include Lannea coromandelica,

Stereospermum neuranthum and Schleichera oleosa.

In DDF, stem densities (individuals/ha) are 3 to 5 times those in the MDF, resulting

in totals between 700 and 1,000 individuals/ha. In comparison with other studies

these figures are high, similar to the findings of KIRATIPRAYOON et al. (1995).

BLASCO (1983) and BUNYAVECHEWIN (1983/a) quote values well below these.

The MDF is characterised by a wide variety of species with more species represented

in higher numbers. The community is dominated by Lagerstroemia calyculata and

Terminalia nigrovenulosa, with Schleichera oleosa, Lannea coromandelica and

Dalbergia and Vitex species co-dominant. The total number lies between 380 and

480 individuals/ha.

In comparison, SAHUNALU et al. (1979) come up with much lower values.

OGAWA et al. (1965) meanwhile quote higher values.


85

However, whether these figures are actually comparable remains uncertain as the

methodologies used were poorly described.

6.5.4 Natural regeneration

In MDF and DDF 36 species were counted. The apparently low figure for the

transition plot PP3 (22 species) is misleading since the area observed was only half

the size of the MDF and DDF plots. Overall, dominance patterns are different in

relation to mature stands of DDF and MDF.

In the permanent plots of the DDF, the two Shorea species accounted for appr. 50%

of the regeneration. In MDF, Terminalia nigrovenulosa was the dominant species in

the regeneration.

Migratory shifts of DDF species into the transition plot PP3 and subsequently from

this transition plot into the MDF could be seen.

No pronounced shift of MDF species to the DDF or into the transition plot PP3 could

be recorded, and only to a limited degree from the transition plot towards the DDF.

Seedling establishment and survival can be linked to climate.

When considering the mortality rates of migrating individuals, differences can be

observed between DDF and MDF species. The DDF species that shift to more mesic

environments have a lower survival rate than MDF species migrating into the more

xeric environment.

Similar observations have been made by CHAMPION et al. (1965, 1968) and

TROUP (1921) in the Indian Sub-Continent and KIRATIPRAYOON et al. (1995).

Whether this is the result of site conditions or due to competition between

individuals remains unclear.

The DDF and MDF sites show high numbers (75,500 and 83,250 individuals/ha,

respectively) of seedlings, the transition zone of PP3 is less densely stocked (30,500

individuals/ha). From a silvicultural perspective, even though these figures include


86

shrub and tree seedlings, there are not enough individuals present for reliable natural

regeneration.

6.5.5 Available light

The assessment and modelling of available light revealed distinct differences

between the two forest types. As first visual assessments and the open structure

suggested, the DDF is characterised by higher light readings at ground level.

Available light correlates to the state of degradation, crown cover and stand density.

Attributable to their three-storey structure, in MDF forests less light reaches the

ground. Figures are nearly 50% lower compared to DDF.

Due to their more uniform canopy structure, compared to DDF, light distribution in

the MDF plots is more homogenous. The DDF/MDF transition plot has the lowest

light readings, attributable to vigorous regeneration and associated high stand

density.

The establishment and reaction of regeneration and saplings to modelled light values

revealed no significant correlations.

Conclusions

Though hemispherical photographs reveal information on the general light patterns

in the stands under consideration, the approach harbours certain limitations.

Photos can only be taken with an overcast sky or before sunrise and after sunset. This

leaves only 20 to 30 mins., or a few pictures per day, taken under considerable risk

of entering the indigenous food chain involuntarily and prematurely.

The one-off sampling of light gave an indication of major patterns of light in the

plots. However, the quality of results could greatly be improved by measuring and

recalibrating the method in light of the prevailing seasonal conditions and the

phenology of the species involved.


87

This method is not suitable for assessing light in specific locations (for example

canopy gaps) since the area covered by the camera ranges from 20 to 25 m radius,

depending on the focal length of the lens.

For any given research location, pictures should always be taken at the same time

and at the same settings. For data collection as a whole, the same camera should be

used to avoid errors resulting from equipment-conditioned differences in light

reading.

6.5.6 Diameter increment via analysis of bore cores

The bore cores taken revealed no results. Though certain species showed ring-like

patterns, it could not be verified whether these were truly annual rings or whether

they were complete or partial.

One of the main species of the MDF, Vitex limoniifolia, revealed measurable tree

rings. However, the sampled trees and the subsequent increment values derived

proved unrepresentative of the study site.

On the other hand, the results confirm the existence of tree rings in tropical species

and are in line with recent research (STAHLE, et al., 1997) on the existence of tree

rings of Vitex keniensis and Pterocarpus angolensis in Zimbabwe.

Conclusion

To improve increment prediction, species have to be found that develop annual rings.

Tree disk and bore core should be combined, together with an analysis of wood

density (SPIECKER, in prep.). For better visual analysis, colouring and chemical

treatment should be conducted. Radiocarbon dating and x-ray densitometry,

successfully applied by WORBES (1995), should be considered for tropical species

too.


88

6.5.7 Distribution of individuals across the social position

The assessment of the Social Position reveals a two-storey structure for the DDF,

with few individuals represented in the dominant layer. The two Shorea species are

present across all Social Positions and command co-dominant and dominant

positions.

The distribution of Social Positions in the MDF is more balanced. A three layer

structure is visible with up to 10 species represented in the upper two layers,

dominated by Lagerstroemia calyculata and Terminalia nigrovenulosa.

Conclusion

In dense stands where access to light is a limiting factor, the assessment of Social

Positions on the basis of DAWKINS’ (1958) method can be regarded as appropriate.

However, in open structured forests such as the DDF, this method has limitations

because in most cases there is no immediate neighbour to which individual trees can

be related.

For any kind of silvicultural treatment it is important to know the light preferences or

demands of the trees occurring at certain developmental stages. The problem of how

to differentiate between light demanding and shade tolerant tree species has been

assessed in different studies (ROLLET, 1980; KAMMESHEIDT, 1994; GRULKE,

1998). ROLLET (1980) showed that in undisturbed humid tropical forests the DBH

class distribution of shade tolerant tree species is left-steep or L-shaped while DBH

distribution of light demanding tree species if anything approaches a more Gaussian

distribution. This pattern has been independently shown in the CHACO of Paraguay

by GRULKE (1998).

However, most assessments of DBH-class distribution are based on an assumption

that the stands investigated were more or less undisturbed. This is unlikely in areas

where deciduous forests prevail. All too often fire and logging have altered DBH


89

distribution patterns and they strongly deviate from the expected inverted J-shaped

curve.

KAMMESHEIDT (1994) attempted to classify the light requirements of individual

species based on parameters independent of disturbance. The following parameters

were tested: successional attitudes, crown architecture and the light compensation

point, with the latter proving the best single indicator. However, measurement error

and standard deviation of this parameter is high, forcing KAMMESHEIDT to rely on

several parameters.

The influence of past logging and fire has to be considered before the species can be

classified according to its light demands.

For most MDF and DDF tree species the question about the light demand of a given

species can not be answered with certainty at this point.

Future research has to assess the light demands of DDF and MDF species across

their development stages and under different states of competition.

6.5.8 Diameter distribution of stands

The maximum DBH reached in DDF is 45 cm. Nearly 70% of all individuals are

represented in the range from 5 to 15 cm DBH, with a sharp drop when shifting to

higher DBH values.

The DBH range in MDF is wider, ranging up to 75 cm. Once more, smaller

diameters dominate the population. However, in relation to a log-normal function the

range between 20 and 40 cm DBH is underrepresented.

Measuring method – Problem of seasonal DBH variation

The annual DBH measurements provided information on increment, but due to the

seasonal shrinkage and swelling of trees, they must be viewed with caution.


90

During 1975 and 1976, SUKWONG et al. (1976) measured swelling and shrinkage

at the Sakaerat research centre in north-eastern Thailand. Swelling of the stem

occurred in May 1975 after the first rains, peaking in September. It ceased following

the onset of the dry season, and showed pronounced stem contraction in January

1976. TANAKA et al. (1995), in a similar study in Kanchanaburi in western

Thailand, recorded negative DBH growth.

Conclusion

The gaps in the diameter distribution curves in some of the MDF stands can be

attributed to previous logging activities, particularly in areas where access was easy.

Recurrent annual fires contribute to this phenomenon by destroying seedlings and

saplings.

In the 2ha MDF plot the evidence of logging was less obvious. Possibly this can be

attributed to its more remote and less accessible position.

For future monitoring, permanent diameter tapes should be attached to selected

individuals and measured on at least a monthly basis to gain reliable data. Cambium

marking could be tried, despite its limitations, as discussed by SASS et al. (1995).

There are considerable threats to permanent measuring equipment from wild

animals, for example monkeys, deer and elephants, which should not be

underestimated. Seed traps and other permanent installations are often destroyed by

the native fauna.

6.5.9 Basal area and volume of stands

Basal areas show distinct differences between DDF and MDF.

DDF stands hold basal areas of between 15 and 18 m2/ha. MDF stands reach up to 25

m2/ha. Annual basal area increment between the different sampling years ranged

from 1% to 5% (percentage of total basal area increment/year). Correlations of basal

area increment and precipitation were not statistically significant.


91

With regards to basal area in DDF communities, KUTINTARA (1975),

SAHUNALU and BUNCHAVECHEVIN (1985) and DHANMANONDA (1995)

achieved similar results (17,6 m2/ha, 14 m2/ha to 19 m2/ha, and 18 m2/ha to 19 m2/ha,

respectively.)

SAHUNALU and DHANMANONDA (1995) recorded DDF basal area increment

between 5 and 7%.

The volume assessments (solid volume over bark) showed similar differences

between the two forest types, with a range between 95 m3/ha and 180 m3/ha in the

DDF and 203 m3/ha and 285 m3/ha in the MDF. In the absence of species-specific

form factors estimates were made with the form factor for Fagus sylvatica.

6.5.10 Crown characteristics and crown projection of stands

The crown distribution pattern in the different forest stands is patchy, with visible

gaps.

The crown projection area of tree species of the DDF is smaller compared to the

MDF species. In the latter, crowns can cover up to 400 m2, whereas the DDF trees

can only reach a 120 m2 maximum crown area.

Conclusion

Though crown projection greatly benefits from taking eight radii (SPIECKER,

1991), individual crowns were assessed by measuring only four perpendicular radii.

Under given constraints this proved time and cost efficient.

6.5.11 Distribution of potential crop trees in stands

Potential crop tree (PCT) selection was primarily based on species and stem quality.

Individuals were selected from all size classes, social positions and growth stages.

The distribution of PCT’s in the sample plots was heterogeneous, with large gaps

prevailing.


92

In the DDF plots, between 50 and 135 individuals/ha could be selected. In MDF

plots appr. 60 individuals/ha met the requirements necessary to be assigned as

PCT’s.

The percentage of PCT’s, when compared to the total population, range from 8 to

13% in the DDF and from 13-17% in the MDF.

To define possible intervention strategies, direct competitors to PCT’s and other,

undesired individuals were also selected.

Conclusion

The low number of PCT’s in the DDF and MDF indicate the restricted potential of

these forest types for such a selection approach. WÖLL (1989); LAMPRECHT

(1990); von der HEYDE (1990) HAHN-SCHILLING (1994) and POKORNY

(1995), recommend between 100 and 300 PCT’s.

However, these figures may be misleading. It should also be kept in mind that these

sites have been subjected to serious disturbance in the past. The low density of

PCT’s is a result of previous logging activity and its effect on stand structure.

It is likely that protection of the stands against fire and illegal logging will improve

the situation.

Growth prognosis for the Mixed Deciduous Forest and silvicultural considerations

93

7 Growth prognosis for the Mixed Deciduous Forest and

silvicultural considerations

Sustainable silvicultural management needs reliable information on the potential of

stands and their future growth and yield. This is collected and monitored over long

periods of time. The information available is often insufficient, as it is in Thailand.

In the following chapter a restricted and conservative growth prognosis for the MDF

stand will be developed. Models were developed and increment functions (see

below) were used favouring the annual DBH measurements because of their higher

stability compared to the shorter term DBH assessment.

As shown before, the DBH measurements are scattered over a wide range and some

DBH classes are not well represented. With annual increments measured between 2

and 15 mm the measurement error can be considered very high. Climatic conditions

(heavy rain or long dry periods) and the swelling and shrinking of bark and wood can

profoundly influence the measurements.

The results of the growth prognosis enable visualisation of the impact of the two

different silvicultural management scenarios.

• Scenario 1: Stand will be left undisturbed to allow for natural growth. No

intervention by treatment, no selection to improve the stand over time.

• Scenario 2: Selection of potential crop trees (compare chapter 3) and removal of

competition (liberation) and trees of low quality (refining).

Because there is no data available on the influence of liberation on the individual

growth of tree species under consideration an assumption was made that increment

functions would remain stable after the removal of competitors. The resulting growth

figures can therefore be considered as the lower threshold or in other words; a

conservative estimate for the growth potential of the Mixed Deciduous Forests. The

calculations are based on a one year prognosis period to give an indication of the


94

possible growth rate. The figures are suitable for only limited extrapolation in time.

For the growth prognosis the data from the 2ha plot will be used. The reason for the

selection of the Mixed Deciduous Forests was the high number of individuals per

species available for calibration and its higher growth potential.

7.1 Deriving empirical models for future stand assessments

Fitting of stand height curves

Scatter plots Height over DBH showed a quite undifferentiated relationship between

tree height and diameter, as specific tree species were not considered. To analyse this

relationship more concisely, stand height curves were calculated and compared. Only

those tree species were considered that had a sampling size of more than 25

individuals (Table 9).

Table 9: Selected species for calculating stand height curves

MDF

Lagerstroemia calyculata

Terminalia nigrovenulosa

Vitex limoniifolia

Schleichera oleosa

Walsura villosa

Stereospermum neuranthum

Xylia xylocarpa

During the analysis obvious outliers were eliminated, counting for a total of only

seven values over all tree species to be removed during this process.

A MICHAILOV-function was chosen as the height function, because it is very

flexible with an inflection point and an asymptotic behaviour (SLOBODA et al.,

1994).


95

The function is as follows:

DBHa

eaheight1

*03.1−

+=

where

height = tree height in m

DBH = diameter at breast height (1.3 m) in cm

A0, A1 = parameters

The function is fitted with a non-linear regression. The results are given in Table 10.

Table 10: Results of the non-linear regression fitting the stand height curves for MDF species

Species N r2 MSE Parameter Estimate Upper ACV

Lower ACV


126 0.56 1.04 A0 A1

29.11 14.25

31.73 16.88

26.49 11.61

Schleichera oleosa 40 0.90 3.96 A0 A1

27.85 12.21

30.52 13.85

25.18 10.58


29 0.61 4.16 A0 A1

17.48 8.71

21.86 11.57

13.09 5.85


92 0.50 4.37 A0 A1

29.75 11.25

33.46 14.00

26.04 8.51

Vitex limoniifolia 54 0.58 9.65 A0 A1

21.67 9.77

24.42 13.12

18.93 6.43

Walsura villosa 36 0.68 0.27 A0 A1

23.33 9.48

26.99 12.14

19.67 6.81

Xylia xylocarpa 27 0.88 6.25 A0 A1

27.25 11.01

30.69 13.67

23.80 8.35


367 0.65 6.87 A0 A1

28.03 13.5

29.67 14.79

26.39 12.21

N = sampling size; r2 = measure of certainty; MSE = mean square error; ACV = asymptotic confidence interval 95%

The r2-values as a measure of certainty are high, but the mean square errors behave

quite differently. Lagerstroemia calyculata and Walsura villosa have small mean

square errors, compared to the high values of Vitex limoniifolia and Xylia xylocarpa.


96

This may indicate that for the latter species the spread of the real values along the

fitted curve is greater than in the case of the two firstly mentioned tree species.

All parameter estimations are statistically significant, as can be seen by the

asymptotic standard errors of the coefficients.

The height curves displayed in Figure 28 allow better comparison than a large

number of points in a scatter plot. Comparison shows that the wide spread of heights

over a given diameter is caused by species specific effects. Stereospermum

neuranthum has the lowest height, Terminalia nigrovenulosa is the highest.

At a given DBH of 30 cm, Stereospermum neuranthum, for example, reaches a curve

height of only 14.4 m, while Terminalia nigrovenulosa has a curve height of 21.8 m.

Over the whole range of tree diameters Terminalia nigrovenulosa maintains the

greatest height values. In contrast, Walsura villosa obviously has a rapid height

growth at low diameters, more rapid than Lagerstroemia calyculata for example, but

at diameters of about 20 cm the height curve of Walsura villosa flattens and drops

below that of Lagerstroemia calyculata which continues upwards.

Terminalia nigrovenulosa, shows distinct height development in early growth stages

and maintains this performance over a long period of DBH growth. Similar strategies

exist for Lagerstroemia calyculata and Schleichera oleosa. They could possibly be

grouped together into similar growth groups. Walsura villosa and Vitex limoniifolia

form another group, again representing the mid layer of the stand.


97

Diameter [cm]

0 10 20 30 40 50 60 70 80

Hei

ght [

m]

0

5

10

15

20

25

30

LAGECALY SCHLOLEO STERNEUR TERMNIGR VITELIMO WALSVILL XYLIXYLO

Figure 28: Comparison of the height curves of selected MDF species. The tree heights are only plotted over the real measured diameter range.

7.2 Development of diameter increment functions

In the first stage of preparing a limited (reserved) prognosis, diameter increment

functions are derived. To this purpose tree species with a sample size of more than

25 individuals are considered with their own increment function. The 7 species are

listed in Table 9. In group “Remaining collective “ all other species are summarised

as one group.

Only linear models are applied:


98

DBHaaid *10+=

with

Id = diameter increment cm/year

DBH = tree diameter in cm

a0, a1 = parameters

The regression analysis fit resulted in measures of certainty that were in general

lower than 0.1, (Table 11) so the degree of explanation is quite low.

Table 11: Regression results of the increment functions

Species N r2 MSE Param.

Estimate Upper ACV

Lower ACV


129

0.00278

9.7066 A0 A1

0.346719 0.001299

0.492772 0.005619

0.200666 -0.003020

Schleichera oleosa

40 0.00985

0.5787 A0 A1

0.188779 -

0.001156

0.259624 0.002706

0.117935 -0.005018


29 0.00348

0.3538 A0 A1

0.171904 -

0.001486

0.306226 0.008244

0.037582 -0.011216


92 0.07065

2.9050 A0 A1

0.114944 0.005775

0.225090 0.010211

0.004799 0.001338

Vitex limoniifolia

54 0.08028

1.4753 A0 A1

0.143049 0.003301

0.250868 0.006580

0.035230 0.000022

Walsura villosa

36 0.01308

0.4667 A0 A1

0.139454 0.001382

0.236353 0.005703

0.042554 -0.002939

Xylia xylocarpa

27 0.04036

0.22414

A0 A1

0.094054 0.001773

0.186877 0.005502

0.001232 -0.001956


366

0.03871

12.1948

A0 A1

0.177974 0.003408

0.226167 0.005173

0.129782 0.001643

N = sampling size; r2 = measure of certainty; MSE = mean square error; ACV = asymptotic confidence interval 95%


99

The reason for these results may be found in the model itself because it does not

include any relevant competitive situation data for single trees, and structure is of

course responsible for growth dynamics. The model was not improved by including

more variables like tree height or the tree’s social position. Another factor was that

the increment came from two assessments which included only a one year increment,

so the increments are not very stable. They have to be seen as a first indication of the

potential of this forest community, not as an absolute figure.

Despite these regression analysis results the fitted functions display highly variable

behaviour for each tree species and species group respectively (Figure 29).

Diameter [cm]

0 10 20 30 40 50 60 70 80 90 100

Dia

met

er In

crem

ent [

cm]

0,0

0,1

0,2

0,3

0,4

0,5

LAGECALY SCHLOLEO STERNEUR TERMNIGR VITELIMO WALSVILL XYLIXYLO

Figure 29: Diameter increment of selected species. The increment for the respective MDF species are plotted over the real DBH range without extrapolations.

For most species the diameter increment is between 10 and 20 mm in the lower DBH

range and increases gradually with age and higher DBH. Terminalia nigrovenulosa

displays a higher increment exceeding even Lagerstroemia calyculata in the higher

DBH range. Most species increase their increment over time and growth, except


100

Stereospermum neuranthum and Schleichera oleosa. Lagerstroemia calyculata has

the highest increment at the lower DBH range at more than 30 mm, but the increase

in diameter increment over time is relatively small.

It is important to recognise that these functions are not valid as increment functions

over a very long period of time or in different stand structures. They are statistically

valid for the given situation.

7.3 Development of height increment functions

For the species under consideration the height increment over time is unknown.

During the second assessment no tree heights were measured because the expected

measurement error could be much higher than the expected increment.

For deriving height increment data, stand height curves previously calculated were

used.

For a given tree diameter the actual height is:

DBHa

eaheight1

*03.1−

+=

where

Height = tree height from stand height curve (in m)

DBH = tree diameter (in cm)

a0, a1 = parameters of the respective stand height curve

Now the new tree height is:

idDBHa

eanewh +−

+=1

*03.1)(

where

h(new) = new tree height from stand height curve

id (annual)= tree diameter increment from the increment curve (in cm)

DBH = tree diameter in cm

a0, a1 = parameters of the respective stand height curve


101

So the tree grows along the stand height curve, which is a reasonable assumption for

stable stand structure situations. (Annual height increment is ih= h(new)-h)

7.4 Restricted prognosis of the growth potential in Mixed

Deciduous Forests

The derived diameter and height increment functions now serve as a base for growth

predictions over a given prognosis period.

Within this growth prediction for every tree in the stand the following steps are

applied:

• Step 1: calculate the diameter increment with the diameter increment function

• Step 2: calculate the new tree height with the height increment function

After the diameter and height increment of each individual is calculated the increase

in basal area and volume will be determined to assess potential growth and yield of

the Mixed Deciduous Forests.

As information on the development or growth of the different groups of individuals

is important, the growth prognosis is threefold:

• In the first assessment the stand will be treated as one entity

• In the second assessment only the potential crop trees will be considered

• In the third and last assessment the stand will be looked upon after liberation

treatment has occurred.

To keep an in-growing population of small trees it must be assumed that the smallest

diameter class is filled up every year to replace the outgrowing individuals. The data

base for the calculations is the 2ha-MDF-plot.

With this procedure a yearly total volume increment of appr. 5 m3/ha can be derived

as can be seen in Table 12.


102

Table 12: Volume increment table for the 2ha plot, all individuals

DBH DBH [cm] height [m] N Basal area [m2] Volume [m3]

Class old new old new old new Diff Old new Diff. old new Diff.

1 7.5 7.6 6.4 6.6 145 143 -2 0.66 0.68 0.02 1.69 1.79 0.10

2 12.4 12.5 11.1 11.2 112 112 0 1.37 1.39 0.02 6.67 6.88 0.21

3 17.4 17.5 14.5 14.5 110 109 -1 2.64 2.65 0.01 17.90 18.10 0.20

4 22.1 22.2 17.0 17.0 100 99 -1 3.85 3.83 -0.02 31.94 31.79 -0.15

5 27.3 27.4 18.7 18.8 84 85 1 4.94 5.02 0.08 46.28 47.31 1.03

6 32.2 32.3 20.2 20.2 58 59 1 4.72 4.83 0.11 48.43 49.63 1.20

7 37.0 37.1 20.7 20.7 51 51 0 5.50 5.53 0.03 58.40 59.01 0.61

8 42.3 42.3 21.5 21.4 39 38 -1 5.49 5.35 -0.14 61.04 59.18 -1.86

9 47.2 47.3 21.6 21.8 29 32 3 5.07 5.63 0.56 57.06 63.64 6.58

10 52.6 53.0 23.4 23.4 16 16 0 3.48 3.53 0.05 42.55 43.21 0.66

11 56.9 57.3 23.4 23.4 10 10 0 2.54 2.58 0.04 31.14 31.61 0.47

12 62.6 62.7 23.6 23.5 8 7 -1 2.46 2.16 -0.30 30.41 26.51 -3.90

13 67.5 66.9 23.6 23.6 5 5 0 1.79 1.76 -0.03 22.16 21.76 -0.40

14 73.6 72.7 24.6 24.7 2 3 1 0.85 1.24 0.39 10.96 16.08 5.12

15 76.5 76.9 24.8 24.8 2 2 0 0.92 0.93 0.01 11.93 12.08 0.15

∑ 2 ha Total 771

Total 771

46.28 47.11 0.83 478.56 488.58 10.02

∑ 1 ha 23.14 23.56 0.41 239.28 244.29 5.01

For clarity the trees are grouped into DBH classes of 5 cm range, starting with class

1 ranging from 5 - 10 cm, class 2 from 10 - 15 cm, etc. All growth predictions are

based on the total population of the 2ha plot to incorporate the maximum species and

diameter range. The total volume (solid volume over bark) in the 2 ha plot totals

239.28 m3/ha. A small difference to the 239.93 m3/ha which was calculated in the

basic yield table (compare the 2ha plot yield table in Appendix 2) was caused by

using stand height curves instead of real tree heights. This negligible difference is


103

also proof of the usefulness of the stand height curves in reaching an unbiased

estimation of stand volume. Table 12 shows that for example, in the DBH-Class 7 a

mean DBH of 37 cm at the onset of the growth prognosis. As the mean value in the

class is not identical to the centre of the class (real 37 cm vs. 37.5 cm as class

middle) it is obvious that the stem numbers in the class are not distributed equally.

Figure 30 displays the movements and shifts between the diameter classes.

DBH-Classes

0 2 4 6 8 10 12 14 16 18

Num

ber

of In

divi

dual

s

-3

-2

-1

0

1

2

3

4

Shift between classes

Figure 30: Changes in stem number diameter distribution in the first (year) prognosis

period

In the first DBH-Class for example, a loss of 2 stems (per 2 ha) can be observed.

Those two individuals grew up into the next DBH-Class. This loss in the first group

would naturally be replenished with in-growing saplings but because of a lack of

reliable data this was not considered here.

7.5 Growth and yield of potential crop trees

Looking at the potential crop trees in a second prognosis, the focus is directed to the

economically most important sub-population of the stand. Table 13 summarises the

characteristics in tree dimensions and increment over the DBH-classes.


104

Table 13: Volume increment for the potential crop trees


Class old new old new old new Diff. Old new Diff. old new Diff.

1 7.6 7.8 6.9 7.1 8 8 0 0.04 0.04 0.00 0.11 0.11 0.00

2 12.1 12.3 11.4 11.5 6 6 0 0.07 0.07 0.00 0.34 0.36 0.02

3 17.4 17.6 15.2 15.3 18 18 0 0.43 0.44 0.01 3.06 3.17 0.11

4 22.5 22.6 17.8 17.8 21 20 -1 0.84 0.80 -0.04 7.28 7.00 -0.28

5 27.6 27.5 19.7 19.7 22 21 -1 1.32 1.25 -0.07 13.03 12.37 -0.66

6 31.6 31.7 21.0 21.0 16 18 2 1.26 1.43 0.17 13.52 15.30 1.78

7 37.1 37.4 21.2 21.3 13 13 0 1.41 1.43 0.02 15.38 15.65 0.27

8 43.1 43.3 21.6 21.6 6 6 0 0.87 0.89 0.02 9.78 9.93 0.15

9 46.9 47.2 22.4 22.4 9 9 0 1.55 1.58 0.03 18.11 18.42 0.31

10 52.7 53.0 23.5 23.5 5 5 0 1.09 1.11 0.02 13.37 13.58 0.21

12 63.3 63.7 24.0 24.0 2 2 0 0.63 0.64 0.01 7.90 8.01 0.11

14 72.8 73.2 24.6 24.6 1 1 0 0.42 0.42 0.00 5.36 5.43 0.07

∑ 2 ha 9.93 10.10 0.17 107.24 109.33 2.09

∑ 1 ha 4.97 5.05 0.09 53.62 54.67 1.05

In total the 2 ha plots contain 127 trees of high economic importance (potential crop

trees), resulting in about 64 individuals/ha.

They represent 16% of the individuals in total, 22% of the total stand volume and

21% of the volume increment.

Comparing the number of those trees in the DBH-classes with the stem number

diameter distribution of the total stand reveals that the bigger DBH-classes consist of

more potential crop trees than the smaller DBH-classes. The proportions are about

5% in DBH-classes 1 and 2, reaching about 20 or 30% in the medium and upper

DBH-classes.


105

7.6 Growth and yield of remaining stand (post liberation and

refining)

The stem number diameter distribution of trees directly competing with the potential

crop trees, and trees of low stem quality is depicted in Figure 31. These trees will be

removed under the assumption that harvest of both is economically viable. They are

most widely distributed in the DBH-classes 4 to 8 (i.e. DBH from 20 to 45 cm).

DBH-Classes

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Num

ber

of In

divi

dual

s

0

20

40

60

80

100

120

140

160

Individuals/DBH-classREMOVED/DBH-class

Figure 31: Stem number diameter distribution of removal stand

Table 14 summarises the results of the yearly increment of the 2ha Mixed Deciduous

stand after liberation of the PCT’s and after refining.


106

Table 14: Volume increment table for the 2ha plot, competition and bad quality trees removed


Class old new old new old new Diff. Old new Diff. old new Diff.

1 7.5 7.6 6.4 6.6 140 138 -2 0.64 0.65 0.01 1.64 1.72 0.08

2 12.4 12.5 11.1 11.2 108 108 0 1.31 1.34 0.03 6.41 6.60 0.19

3 17.4 17.5 14.4 14.5 102 102 0 2.44 2.47 0.03 16.50 16.86 0.36

4 22.0 22.1 16.9 16.9 84 83 -1 3.21 3.20 -0.01 26.53 26.43 -0.10

5 27.3 27.4 18.7 18.8 71 71 0 4.17 4.19 0.02 38.93 39.32 0.39

6 32.1 32.1 20.1 20.1 42 43 1 3.41 3.49 0.08 34.92 35.75 0.83

7 37.1 37.2 20.5 20.6 39 40 1 4.21 4.35 0.14 44.43 45.96 1.53

8 42.5 42.5 21.4 21.3 23 22 -1 3.27 3.12 -0.15 36.16 34.48 -1.68

9 47.0 47.1 21.4 21.5 20 22 2 3.47 3.84 0.37 38.52 42.89 4.37

10 52.7 53.1 23.3 23.4 7 7 0 1.53 1.55 0.02 18.67 18.96 0.29

11 57.5 57.9 23.7 23.8 2 2 0 0.52 0.53 0.01 6.46 6.56 0.10

12 62.7 62.6 24.1 24.0 5 4 -1 1.55 1.23 -0.32 19.58 15.53 -4.05

13 65.3 65.4 20.0 22.3 1 2 1 0.33 0.67 0.34 3.47 7.85 4.38

14 72.8 73.2 24.6 24.6 1 1 0 0.42 0.42 0.00 5.36 5.43 0.07

15 75.0 75.4 24.7 24.7 1 1 0 0.44 0.45 0.01 5.72 5.79 0.07

∑ 2 ha 30.92 31.50 0.58 303.30 310.13 6.83

∑ 1 ha 15.46 15.75 0.29 151.65 155.07 3.42

The total volume of competing trees totals 33 m3/ha. The removal stand volume

would total 88 m3/ha. The loss in total volume increment would add up to

approximately 1.5 m3/ha/year, if the competitors and trees of low quality could be

removed immediately, the remaining stand would reach an increment of 3.4

m3/ha/year (Table 14)


107

Conclusion

Without any intervention, volume increment is estimated at about 5 m3/ha/year.

Increment of potential crop trees is about 1 m3/ha/year. Though crop trees account

for only 16% of the population total, they contribute 21% of the total increment of

the stand, demonstrating the powerful influence of potential crop trees on the total

volume increment of the stand.

The final growth prognosis results in a volume increment of 3.4 m3/ha/year.

An estimated annual increment of 2.1% compares with previous research by

SADOFF (1995) in similar forest types. She quotes annual growth rates of 2.5%.

Increment values obtained appear sufficiently high to justify silvicultural operations.

However, considering the specific heterogeneity and the assumptions made in the

underlying model, results should not be extrapolated over extended periods of time.

Similarly, for site specific silvicultural decision-making more information on the

growth and response to treatment of individual species is required.

Discussion

109

8 Discussion

In Dry Dipterocarp Forests and Mixed Deciduous Forests experimental plots were

established to research structure, composition and dynamics. Growth and yield were

analysed and the management possibilities and silvicultural potential of the Mixed

Deciduous Forests investigated.

8.1 Comparability of the Huay Kha Khaeng study site

8.1.1 Forest-type delineation and differentiation

Due to the absence of up-to-date aerial photographs of sufficiently high resolution,

line sampling and subsequent Cluster and Correspondence Analysis were applied to

delineate and differentiate forest types.

The numeric nature of such results provided a number of important advantages over

visual assessment of aerial photographs:

• Numeric results can be compared directly to other studies.

• It enables objective selection and placement of representative long-term

observation plots.

• Selection and placement could be verified statistically.

On the basis of the assessment of species composition and structure, both forest types

could be described and distinguished. The sample size of 76 plots for this assessment

proved to be sufficient to capture the floristic and structural features of the individual

community-types involved. This could be verified by developing community-

specific species-area curves.

On the basis of a fine-stratification of community-types, it is possible to relate

specific stand parameters to individual clusters. Similarly, existing literature on the

subject confirms our own findings.


110

Our own results regarding species richness, stem densities and basal area fall within

quoted ranges, though our stem densities were often lower. This can perhaps be

attributed to methodological differences, particularly with regards to site selection.

Especially in DDF, stem densities in juvenile stands can be high.

The plots selected for long-term observation and detailed stand parameter assessment

represent the two forest-types and their respective sub-types. This could be verified

by comparing the environmental and stand parameters of permanent plots to the

parameters that prevail in the temporary plots. Similar verifications derived from

placing the permanent plots into the correspondence reference-framework created by

temporary plots.

The outcome of cluster and correspondence analysis was strongly influenced by the

choice of input parameters. Because the relationship between DBH and basal area is

quadratic, basal area values give higher weight to large individuals. In contrast,

abundance values give more weight to small individuals. The relationship between

DBH and abundance is inverse.

Subsequently, dominance is more suited to describe the mature phases of a stand-

structure while abundance values are better suited to describing juvenile stands; in

other words, the first is more suited to speculation on potential “climax” types, the

second to evaluating past/recent impacts and to anticipate future trends.

To allow for between-stand comparison it proved necessary to use relative values.

Log-transformation of relative values helped to reduce unwanted weighing, in a

situation where little was known of the ecological significance of individual species.

8.1.2 The characteristics of prevailing forest types

As explained in previous chapters, in the past research focussed mainly on structure

and composition of the forests under consideration.

With the set-up of permanent plots, the foundation for long-term assessment of

growth and yield could be established.

Discussion

111

Common to both DDF and MDF are:

That stands are heterogeneous with regards to floristic composition and structure.

This is also strongly conditioned by previous logging and fire, with diameter-class

specific stem distribution irregularly scattered. The table below summarises

silvicultural aspects differentiating the two forest types.

Table 15: Differences in structure and occurrence of DDF and MDF

Parameter DDF MDF

Site conditions

Found on marginal sites with shallow soils of low water holding capacity.

Found on sites with deep and fertile soils of good water holding capacity.

Specific composition and dominance pattern

Dominated by two species. Many species with low frequency. High stem density, low basal area, rich in small diameter individuals, few large-size individuals, maximum DBH at 45 cm.

Species-rich, undefined dominance pattern, many climbers . Low stem density, high basal area, poor in small diameter individuals, maximum at 80 cm DBH.

Horizontal structure

Small crowns, discontinuous cover. Grouped occurrence of individuals.

Large crowns, continuous cover with small gaps.

Vertical structure

Two tree-layers , ground cover dominated by grasses.

Three-layered. Mid-layer dominated by large-sized, shade tolerant species, ground layer with high proportion of shrubs/perennial herbs.

Growth potential

Low High

Regeneration condition

Abundant regeneration of the dominant species Shorea siamensis and S. obtusa.

Mostly sufficient regeneration of the main species.


112

8.1.3 Growth prognosis

One of the major shortcomings of research into deciduous forest is the virtual

absence of information on stand dynamics. Attempts at tracing annual diameter

increment via bore cores sampling yielded no results. Early and latewood

differentiation in species investigated is missing or hampered by false or incomplete

rings.

However, relationships exist between DBH and tree height and DBH and crown

width, permitting growth prediction. Based on similarities in their height

development patterns, species can be grouped into three main categories.

On the basis of the DBH and tree height relationship, a restricted growth model was

developed. Currently, the relative annual volume increment of the stand equals 2.1%

(5 m3/ha/year).

In a further step possible semi-natural silvicultural options were evaluated. The aim

was to modify stand structure, so that economically viable management can be

facilitated. On the basis of a PCT’s selection approach, liberation and refinement

strategies were simulated.

Since the growth model assumes increment to be linear during the lifetime of an

individual and pays no attention to changing relationships between competing

individuals, qualitative improvement of stands resulted in apparent growth being

reduced to 3.4 m3/ha/year.

However, it can safely be assumed that liberation and refinement and the associated

improvement in growing-space availability will lead to an increase and concentration

of increment on individuals liberated from competition. Though this will be

concentrated on those that are physiologicallycapable of responding to additional

growing space, overall growth should increase.

In summary, the prognosis suggests a potential for silvicultural management.

Discussion

113

Increment values should be seen as a low threshold following liberation. Actual

quantification will require further research.

8.2 Silvicultural implications of the study

Assessment of potential crop trees (PCT’s) gave an indication for the silvicultural

potential of the DDF and MDF. However, in comparison to assumptions made

regarding other deciduous tropical forests (LAMBRECHT, 1990) stem densities are

insufficient. In most cases this can be attributed to stand history – in the investigated

DDF stands this process can be so advanced that PCT’s management schemes are

not advisable. However, considering the large number of regenerating individuals

present, and assuming efficient protection against illegal use and fire, the MDF

stands have the potential to recuperate.

As a result of the low growth potential and the degree of disturbance commonly

encountered, many areas of DDF must be considered unsuited for advanced forms of

management. Costs would not justify benefits and such areas might better be

assigned to the protection of biodiversity and delivering environmental services.

Only areas of higher growth potential can justify advanced silvicultural operations.

Considering the layered structure of DDF, the specific uniformity of stands and the

high densities of regeneration usually encountered, such DDF stands would appear

suited for shelterwood systems as widely practiced on the Indian Sub-Continent.

Clear-cuts are unsuited since they would cause soil erosion and excessive exposure

of regeneration.

Stands that occur in transition are characterised by the higher growth rates and

presence of a proportion of species of the MDF community. They require a

silvicultural approach that either recognises the increasing structural and floristic

complexity or may be converted to structures resembling DDF or MDF.

The heterogeneous stand structure of MDF favours selective management, harvesting


114

and regeneration approaches. Provided growth is sufficient to recover the costs of

initial operations, transformation and improvement can be envisaged.

Transformation would include changing of composition and structure in the form of:

• Spacing and liberation of future crop trees

• Elimination of poor quality stock

• Selection and fostering of species of high economic value and ecological

importance

• Assistance of regeneration to fill gaps in the PCT matrix

• Development of layered forest into an upper crop layer and a lower regeneration

layer

• Possibly enrichment planting.

The below paragraphs serve to compare two management extremes: a low and a

high-intensity conversion.

MDF scheme one: High intensity interventions

In the long-term management should focus on increasing the economic value of the

future stand. In particular, the proportion of high value timber species and crop

quality must be improved.

The following operations are required as first steps:

• Establishment of a feeder road and skidding trail system

• Stock-taking and selection of PCT’s

• Liberation of PCT’s from tree competitors, cutting climbers

- Harvest of marketable individuals within the competitor group

- Other competitors require either cut-to-waste, girdling or chemical elimination

so as to ensure that they do not interfere with PCT’s .

Discussion

115

• Removal of individuals comprising the matrix between the PCT’s and their

respective competitors so as to:

- Retrieve the highest possible value from the standing crop

- Ensure the development and selection of subsequent PCT’s (“Wulf” trees that

obstruct others)

• To encourage natural regeneration

- To enable the fostering of high quality timber species

- In situations where regeneration is insufficient or species composition

unsuitable for transformation, enrichment planting of native, high-value

species should be envisaged

Subsequent steps include regular tending operations so as to:

• Ensure sufficient growing space of PCT’s

• Gradually increase the number of potential crop trees through

- Further liberation emerging PCT’s

- Encouragement of natural regeneration

MDF scheme two: Low-intensity interventions

An alternative strategy could be aimed at situations where growth potential is limited

and the present crop of low value. Requiring little input, it would serve to recover the

costs of the initial silvicultural operations and to minimise the operational costs in

successive steps. Long-term, such silvicultural transformations would be more

gradual than above described approach and will not fully utilise the silvicultural

potential of the stand. However, lower returns are partly compensated for by lower

investment costs.

As a first step, the following operations are required on sites that are accessible with

a minimum amount of access roads and skidding tracks:

• Stock-taking and selection of PCT’s


116

• Liberation of PCT’s from tree competitors, climber cutting

- Harvest of marketable individuals within the competitor group and the in-

between matrix so as to retrieve the highest possible value from the standing

crop

- Other competitors require either cut-to-waste, girdling or chemical elimination

so as to ensure that they do not interfere with PCT’s .

• Encouragement of natural regeneration. Valuable timber species should be

fostered.

Subsequent steps will include regular tending operations. However, to minimise

costs operations should be delayed as long as possible. Specific operations will serve

to:

• Ensure sufficient growing space of PCT’s

• Gradually increase the number of potential crop trees through

- Further liberation of emerging PCT’s

- Encouragement of natural regeneration

As described above, there are possibilities for using the remaining forest resources in

Thailand and in other countries with similar problems, for example Laos, upper parts

of Vietnam and Myanmar. The recommendations given here are based on a limited

study site and can only touch upon possibilities. Silviculture management is

complex, especially under tropical and sub-tropical conditions were no long term and

comprehensive growth and yield data base exists. Future research has to move away

from being solely focused on conservation and habitat protection to incorporate the

economic potential of the remaining forest resources.

Timber prices continue to increase and with every increase the incentives for illegal

loggers become stronger. Laws and regulations can not prevent the cutting down of

trees, neither large nor small scale logging can be stopped.

Discussion

117

Market forces have long been neglected and it is important that the government and

its agencies finally realise that their previous efforts have not been sufficient to

protect the forests. The timber demand is real and without legal supplies the

notorious timber mafia will always find ways to satisfy its customers.

With the proposed country wide inventory, which in actual fact is now under way,

new assessments can be made, based on real data and not on assumptions as in the

past. When combined with aerial photo analysis and remote sensing, hot spots and

sites with high potential for timber quality improvement can be identified. The

results of this assessment can support the Royal Forest Department in targeting and

improving areas with the potential to provide high quality timber.

This can only be achieved through engaging local communities in protection and

sharing revenues with the community base. Similar protection schemes, i.e. close to

Khao Yai National Park are considered very successful. Villagers, together with

local NGOs achieved regeneration of a very degraded forest in 10 years. Clear guide

lines were developed on forest protection and subsequent utilization of timber and

non-timber products. Participation of local communities and access to the resource

were key to the success of this project and similar schemes could be used for other

highly degraded forest areas. The community forest law will eventually provide the

base not only for villagers to gain legal access, but also to improve silvicultural

management in degraded forests.

8.3 Necessary preconditions for deciduous forest management in

the region

Moving away from questions as to whether and how these forests can be managed

sustainably from a ecological-technical perspective, the following chapter serves to

highlight the shortcomings of the wider sphere of the subject that prohibit successful

forestry.


118

Though the Thai Forestry Master Plan may be seen as a first reaction to prevailing

problems, current forestry in Thailand must be considered unsustainable, both from

the silviculture management perspective as well as for political and administrative

reasons.

From a silvicultural and technical perspective, one of the most urgent issues to be

addressed is a clear delineation of forest areas and management compartments. This

requires nation-wide forest inventories. Improved management plans need to be

devised, with fire management as an integral element.

Any political or administrative approach has to be seen as a post-logging-ban-

action. The ban currently in place inhibits effective management. To change this

situation, the relevant political and administrative institutions need to address the

problems behind the symptoms.

Illegal logging is primarily an issue of neglected rural development, unclear

ownership issues and ineffective management of the resource itself. Sustainable

forestry requires an integrated and interdisciplinary approachregarding delineation of

areas suited for sustainable forestry. This includes a revision of the national parks,

conservation areas and wildlife sanctuaries.

Subsidies, tax relief and other incentives should be applied as strategic tools to

encourage sustainable forest management and - where necessary and appropriate –

reforestation.

To overcome the intrinsically linked issues of land ownership, access to resources,

economic development in rural areas and sustainable forest management, alternative

approaches need to be pursued. This includes community forestry, provided the

forest administration itself is capable of supporting such a policy.

This is not the case at present, mainly because the current system of forestry

education is – to put it mildly – outdated, when it comes to the silvicultural

management of natural forests. In contrast to state-run forestry, successful forestry

Discussion

119

involving local populations requires a client-orientated forestry service with suitable

training. Similarly, sustainable semi-natural silviculture requires silvicultural-

technical training that is ecosystem-focussed, applied and based on sound economic

principles. In this sense, the closure of the only school training forest technicians

must be considered a retrograde step that requires rethinking.

8.4 Research needs

8.4.1 Ecological

To support the development and implementation of a semi-natural silvicultural

approach it is absolutely essential to develop a nation-wide system of permanent

observation plots monitoring growth and yield of different forest types. To improve

the quality of the applied growth prognosis, information on the growth functions of

individual species is necessary, as well as on the effects of fire on tree growth.

Knowledge of the phenology and physiology of indigenous species has to be

improved. There is virtually no information on shade-tolerance/light-requirements,

response to competition, to liberation and the factors controlling seed production and

mast years. The impact of fire on germination needs investigation.

For silvicultural reasons it is necessary to kill standing trees, particularly in early

silvicultural conversion phases. The species-specific response to arboricides and

appropriate and environmentally safe application methods should be tested.

8.4.2 Methodological

Field surveys require trained and experienced field staff,the lack of knowledge of

taxonomy proved particularly troublesome. There is an urgent need for more applied

research and documentation regarding taxonomy.

Information is needed on the climatically conditioned seasonal fluctuations in tree

diameters and on the best time of the year to monitor increment.


120

8.4.3 Silvicultural

In MDF, semi-natural silviculture must avoid the short-comings of traditional

selection systems. Harvesting based on a minimum DBH and a fixed rotation length

must be replaced with a selection system based on species-specific crown-space

requirements, quality and maturity of individuals and the condition of the

regeneration. Research should focus on methods of stand transformation aimed at

producing structures suited for thinning from above.

To arrive at the desired regenerational composition and density, research has to be

initiated to control and steer the development of seedlings and saplings, including

prediction of seed years, soil surface treatments to improve germination rates and

early tending methods to control species composition and to ensure rapid seedling

establishment. Similarly, information is required on the capacity of post-fire

vegetative regrowth of tree species and on ways to manage this.

Semi-natural silviculture leads to complex stand structures. To avoid unnecessary

damage to the regeneration and remaining trees, appropriate harvesting and transport

techniques need to be developed. Considering the lack of capital, infrastructure and

the sometimes difficult terrain, improved methods of livestock haulage should be

considered.

8.5 Final conclusion

The methods applied produced the desired results. Stands can be differentiated

objectively and growth can be estimated. Though the stands investigated grow on

marginal or intermediate sites, the estimated increment justifies intensive

silviculture. Possible silvicultural systems in MDF include selection approaches as

well as conversion systems aiming toward simplified, more uniform structures.

From a silvicultural-technical perspective, both systems can be managed sustainably.

However, the current political and administrative climate prohibits this. The future of

the forests and forestry in Thailand will depend on whether the society is able to

Discussion

121

adjust its perception of and its attitude towards the environment. Forests are a vital

but limited resource. They serve as a source of timber and food, as a biodiversity

gene pool, and to protect watersheds.

Sustainable management requires that short-term gains are forgone for the benefit of

future generations and to realise the forests true value by allowing their full

productive potential to be achieved. The full participation of all groups involved or

affected and the equitable distribution of benefits are pre-requisites to encouraging

sustainable management. Furthermore, the ‘loan’ the society has taken from forests

in the past in the form of gross over-cutting has to be repaid if the forests are to

recover. Forest management needs investment in the form of subsidies.

What is needed is a two-way approach, one focusing on the structure of higher-level

policy making, and the other on actual management. Forestry must be conducted

scientifically. Policy-making and subsequent planning has to clearly describe the

nation’s will, and to clarify methods and pathways for achieving this.

In August 2001, a major storm caused widespread flooding in the northern

watersheds and resulted in the deaths of many people and destruction of fields and

upland forests. Environmentalists and the general public called for measures to

conserve and protect Thailand’s forests. One has to realise that protection and

conservation do not come cheap or quickly. Managed forest can generate revenues

for the state and for local communities, thereby increasing their value to become an

important source of stable income. Only then are local communities able to protect

their forests, as they have done in the past.

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123

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Appendix

133

10 Appendix

10.1 Species list and their respective code (sorted by their CODE)

FAMILY GENERA SPECIES VERNACULAR CODE MIMOSACEAE Acacia comosa Gagnep. Nam-hun ACACCOMO MIMOSACEAE Acacia megadalena var.

indo-chinensis Nielsen

Nam-ee-rat ACACMEGA

MIMOSACEAE Acacia pennata Willd, sub-sp. insuavis Nielse.

Kruea-bung-ohn

ACACPENN

RUTACEAE Aegle marmelos Corr. Ma-doom AEGLMARM CAESALPINIACEAE Afzelia xylocarpa Craib Makhaa-mong AFZEXYLO ALANGIACEAE Alangium salviifolium

Wang., var. hexapetalum

Prooh ALANSALV

MIMOSACEAE Albizia lebbeckoides Benth.

Kang ALBILEBB

MIMOSACEAE Albizia odoratissima Benth.

Khee-mod ALBIODOR

MELIACEAE Amoora cuculata Ta-suea-lek AMOOCUCI ANACARDIACEAE Anacardium occidentale Linn. Ma-muang-hin-

ma-pran ANACOCCI

COMBRETACEAE Anogeissus acuminata Wall. var. lanceolata Clarke

Ta-kien-nuu ANOGACUM

ANNONACEAE Anomianthus dulcis Sincl. Nom-hua ANOMDULC STILAGNIACEAE Antidesma ? Maeng-mao-yai ANTIDES1 STILAGNIACEAE Antidesma sootepense

Craib Maeng-mao-soi ANTISOOT

STILAGNIACEAE Antidesma velutinosum Bl. Maeng-mao-kwaai

ANTIVELU

EUPHORBIACEAE Aporusa ficifolia Baill. Mueat-konn APORFICI EUPHORBIACEAE Aporusa villosa Baill. Mueat-khee-

kwaai APORVILL

ANNONACEAE Artabotrys siamensis Miq. Ka-dang-nga-paa

ARTASIAM

SAPINDACEAE Arytera xerocarpa Adelb. See-funn ARYTXERO BAMBUSOIDAE Bambusa arundinaria

Willd. Pai-nahm BAMBARUN

CAESALPINIACEAE Bauhinia glauca Wall. ex. Benth.

Chong-kho-kruea

BAUHGLAU

CAESALPINIACEAE Bauhinia montandra Kurz Chong-kho BAUHMONT TILIACEAE Berrya mollis Wall. ex.

Kurz Po-liang-fai BERRMOLL

BOMBACACEAE Bombax anceps Pierre Ngiu-paa BOMBANCE


134

FAMILY GENERA SPECIES VERNACULAR CODE BOMBACACEAE Bombax valetonii Hochr. Nunn-paa BOMBVALE EUPHORBIACEAE Bridelia retusa Spreng. Teng-nam BRIDRETU ANACARDIACEAE Buchanania latifolia Roxb. Ma-muang-hua-

maeng-wan BUCHLATI

PAPILIONACEAE Butea monosperma Ktze.

Tong-ta-ma-chat

BUTEMONO

STERCULIACEAE Byttneria pilosa Roxb. Kruea-khao-kham

BYTTPILO

CAESALPINIACEAE Caesalpinia sappan Linn. Fahng CAESSAPP ANNONACEAE Cananga latifolia Finet. &

Gagnep. Foehng CANALATI

BURSERACEAE Canarium subulatum Guill. Ma-lueam CANASUBU CAPPARIDACEAE Capparis sepiaria Linn. Nam-kiau-kai CAPPSEPI BARRINTONIACEAE Careya sphaerica Roxb. Kra-don CARESHAE FLACOURTIACEAE Casearia grewiaefolia

Vent. Kruai-paa CASEGREW

CAESALPINIACEAE Cassia fistula Linn. Khuun CASSFIST CAESALPINIACEAE Cassia garrettiana Craib Samae-saan CASSGARR MELIACEAE Chukrasia velutina Wight &

Arn. Mayom-hin CHUKVELU

RUTACEAE Clausena ? Ee-chaen CLAUSEN1 COMBRETACEAE Combretum procursum Craib Sa-kae-kruea COMBPROC COMBRETACEAE Combretum punctuatum Bl. Sa-kae-bueak-

waa COMBPUNC

EHRETIACEAE Cordia cochinchinensis Pierre

Mann (tamada) CORDCOCH

EHRETIACEAE Cordia dichotoma Forst.f.

Mann-muu CORDDICH

EHRETIACEAE Cordia ? Mann-buu CORDIA1 EHRETIACEAE Cordia ? Mann-plah CORDIA2 EHRETIACEAE Cordia ? Mann-pruuh CORDIA3 GUTTIFERAE Cratoxylum formosum Dyer Tiu-daeng CRATFORM GUTTIFERAE Cratoxylum ? Tiu CRATOXY1 EUPHORBIACEAE Croton oblongifolius

Roxb. Plao-yai CROTOBLO

CYCADACEAE Cycas siamensis Miq. Prong CYCASIAM PAPILIONACEAE Dalbergia candenatensis

Prain Sa-khee DALBCAND

PAPILIONACEAE Dalbergia cultrata Grah. ex. Benth.

Kra-phee-khao-kwaai

DALBCULT

PAPILIONACEAE Dalbergia ? Kra-phee-(ta)-khram

DALBERG1

PAPILIONACEAE Dalbergia oliveri Gamble Pra-duu-ching-chan

DALBOLIV

PAPILIONACEAE Dendrolobium ? Kra-dook DENDROL1 DILLENIACEAE Dillenia ? Saan DILLENI1 EBENACEAE Diospyros castanea

Fletcher Makhaa-moi DIOSCAST

Appendix

135

FAMILY GENERA SPECIES VERNACULAR CODE EBENACEAE Diospyros decandra Lour. Chan-paa DIOSDECA EBENACEAE Diospyros ehretioides Ruen-kwaang DIOSEHRE EBENACEAE Diospyros martabanica

Clarke Kai-tao DIOSMART

EBENACEAE Diospyros mollis Griff. Ma-gluea-paa DIOSMOLL EBENACEAE Diospyros ? Kiao-gaan-dong DIOSPYR1 EBENACEAE Diospyros transitoria Bakh. Thaan-damm DIOSTRAN DIPTEROCARPACEAE Dipterocarpus obtusifolius

Teijsm. ex. Miq. Hiang DIPTOBTU

ELAEOCARPACEAE Elaeocarpus ? Munn ELAEOCA1 PAPILIONACEAE Erythrina subumbrans

Merr. Thong-lang-paa ERYTSUBU

CAESALPINACEAE Erythrophleum teysmannii Craib Saak ERYTTEYS MYRTACEAE Eugenia aequea Brum.f. Chom-poo-paa EUGEAEQU MYRTACEAE Eugenia cumini Druce Waa EUGECUMI MYRTACEAE Eugenia ripicola Craib Waeh EUGERIPI ASTERACEAE Eupatorium odoratum Linn. Sap-suea EUPAODOR EUPHORBIACEAE ? ? Luean-kwaang EUPHORB1 EUPHORBIACEAE ? ? Luean-kwaai EUPHORB2 FLACOURTIACEAE Flacourtia indica Merr. Ta-khop-paa FLACINDI FLACOURTIACEAE Flacourtia rukam Zoll&Mor. Ta-khop-nam FLACRUKA RUBIACEAE Gardenia ? Nam-grang-paa GARDENI2 RUBIACEAE Gardenia ? Nam-taeng-bai-

yai GARDENI3

RUBIACEAE Gardenia erythroclada Kurz

Ma-kang-daeng GARDERYT

RUBIACEAE Gardenia tubifera Kruea-kroi-nam GARDTUBI BURSERACEAE Garuga pinnata Roxb. Ta-khram (-tha-

kwaai) GARUPINN

RUTACEAE Glycosmis pentaphylla Corr. Saah GLYCPENT VERBENACEAE Gmelina asiatica Linn. Nam-kang-

maeo GMELINA1

TILIACEAE Grewia eriocarpa Po-khaw-tak-2 GREWERIO TILIACEAE Grewia tomentosa Juss. Po-khaw-tak-1 GREWTOME RUBIACEAE Haldina cordifolia Ridsd. Khwau HALDCORD SIMAROUBACEAE Harrisonia perforata Merr. Nam-khan-tha HARRPERF STERCULIACEAE Helicteres angustifolia Linn. Po-khee-tun HELIANGU STERCULIACEAE Helicteres ? Kluai-mai-kok HELICTE1 STERCULIACEAE Helicteres ? Kluai-mai-paa HELICTE2 STERCULIACEAE Helicteres ? Po-ee-niao HELICTE3 STERCULIACEAE Helicteres ? Po-ee-pae HELICTE4 STERCULIACEAE Helicteres isora Linn. Po-ee-bit HELIISOR MALVACEAE Hibiscus ? Ka-chiap HIBISCU1 VERBENACEAE Hymenopyramis brachiata Wall. Gong-gaang HYMEBRAC RUBIACEAE Hymenodictyon excelsum Wall. U-rok HYMEEXCE IXONATHACEAE Irvingia malayana Oliv.

ex. A. Benn. Kra-bok IRVIMALA


136

FAMILY GENERA SPECIES VERNACULAR CODE LYTHRACEAE Lagerstroemia calyculata Kurz Tabaek-plueak-

baang LAGECALY

LYTHRACEAE Lagerstroemia loudonii Teijsm. & Binn

Salao-kiao-muu LAGELOUD

LYTHRACEAE Lagerstroemia speciosa Pers. In-tanin LAGESPEC LYTHRACEAE Lagerstroemia tomentosa Presl Salao-plueak-

baang LAGETOME

LYTHRACEAE Lagerstroemia villosa Wall. Salao-sao LAGEVILL ANACARDIACEAE Lannea coromandelica

Merr. Oi-chaang LANNCORO

LEGUMINOSACEAE ? ? Kruea-rung-daeng

LEGUMIN1

SAPINDACEAE Lepisanthes rubiginosa Leenh.

Ma-huat LEPIRUBI

SAPINDACEAE Lepisanthes tetraphylla Radlk.

Ma-fuang-chaang

LEPITETR

LAURACEAE Litsea glutinosa C.B.Robinson

Ee-menn (tamada)

LITSGLUT

CELASTRACEAE Lophopetalum wrightiana Arn. Dee-mee LOPHWRIG EUPHORBIACEAE Mallotus ? Prao-noi MALLOTU1 GUTTIFERAE Mammea siamensis

Kosterm. Sara-pee MAMMSIAM

BIGNONIACEAE Markhamia pierrei P. Dop. Cae-paa MARKPIER BIGNONIACEAE Markhamia stipulata Seem.

var. kerrii Srague Cae-hang-kang MARKSTIP

MELIACEAE Melia azedarach Linn. Lien-paa MELIAZED MELIACEAE Meliantha suavis Pierre Pak-waan MELISUAV MELASTOMATACEAE Memecylon edule Roxb. Mueat MEMEEDUL MELASTOMATACEAE Memecylon geddesianum

Craib Plong-gaew MEMEGEDD

ANNONACEAE Miliusa lineata Alston Ee-raet MILILINE PAPILIONACEAE Millettia brandisiana Kurz Kra-phee-chan MILLBRAN PAPILIONACEAE Millettia leucantha Kurz Kra-phee

(tamada) MILLLEUC

RUBIACEAE Mitragyna cadamba Miq. Kra-tum-bai-yai MITRCADA RUBIACEAE Mitragyna hirsuta Hav. Kra-tum-kok MITRHIRS RUBIACEAE Mitragyna javanica Koord.

& Val. Kra-tum-nam MITRJAVA

RUBIACEAE Mitragyna speciosa Korth. Kra-tum-tohn MITRSPEC RUBIACEAE Morinda coreia Ham. Yoo-paa MORICORE RUTACEAE Murraya paniculata Jack Kaew MURRPANI RUBIACEAE Nauclea orientalis Linn. Gun-lueang NAUCORIE OCHNACEAE Ochna integerrima Merr. Mueat-khee-

muu OCHNINTE

BIGNONIACEAE Oroxylum indicum Vent. Phee-kaa OROXINDI PAPILIONACEAE ? ? Tua-3-bai PAPILIO1 SAPINDACEAE Paranephelium longifoliolatum

Lec. Lam-yai-paa PARALONG

Appendix

137

FAMILY GENERA SPECIES VERNACULAR CODE RUBIACEAE Pavetta tomentosa Roxb.

ex. Smith Khem-khao PAVETOME

EUPHORBIACEAE Phyllanthus emblica Linn. Makhaam-pom PHILEMBL LAURACEAE Phoebe paniculata Nees Sa-tit PHOEPANI ANNONACEAE Polyalthia viridis Craib Yaang-don POLYVIRI STERCULIACEAE Pterospermum diversifolium Bl. Ka-nann-fai PTERDIVE PAPILIONACEAE Pterocarpus macrocarpus

Kurz Pra-duu PTERMACR

PAPILIONACEAE Pterocarpus ? Pra-duu-kruea PTEROCA1 RUBIACEAE Randia dasycarpa

Bakh.f. Nam-taeng RANDDASY

RUBIACEAE Randia eucodon Schum. Farang-paa RANDEUCO RUBIACEAE Randia longispina Dc. Nam-liang RANDLONG RUBIACEAE Randia nutan A. Dc. Phaa-dap RANDNUTA ANNONACEAE Rauwenhoffia siamensis

Scheff. Nom-maeo RAUWSIAM

RUBIACEAE ? ? Nam-raeng RUBIACE1 RUBIACEAE ? ? Makang RUBIACE2 SAPINDACEAE Schleichera oleosa Merr. Ta-khraw SCHLOLEO DIPTEROCARPACEAE Shorea obtusa Wall. Teng SHOROBTU DIPTEROCARPACEAE Shorea roxburghii

G.Pon. Paa-yom SHORROXB

DIPTEROCARPACEAE Shorea siamensis Miq. Rung SHORSIAM CAESALPINIACEAE Sindora siamensis

Teijsm. ex. Miq. Makhaa-tae SINDSIAM

ANACARDIACEAE Spondias pinnata Kurz Makok-paa SPONPINN BIGNONIACEAE Stereospermum chelonoides (L.f.) Cae-sak STERCHEL STERCULIACEAE Sterculia ? Po (tamada) STERCUL1 STERCULIACEAE Sterculia ? Po-sam-liang STERCUL2 STERCULIACEAE Sterculia foetida Linn. Po-sam-rong STERFOET STERCULIACEAE Sterculia guttata Rox. Po-phan STERGUTT BIGNONIACEAE Stereospermum neuranthum Kurz Cae-saai STERNEUR STERCULIACEAE Sterculia ornata Wall. Po-daeng STERORNA BIGNONIACEAE Stereospermum personatum

Chatterjee Cae-hin STERPERS

STERCULIACEAE Sterculia villosa Roxb. Po-tuup-huu-chaang

STERVILL

STRYCHNACEAE Strychnos nux-blanda A. W. Hill

Tomm-kaa STRYNUXB

COMBRETACEAE Terminalia alata Heyne ex Roth

Rok-faa TERMALAT

COMBRETACEAE Terminalia bellerica Roxb. Samo-phi-phek TERMBELL COMBRETACEAE Terminalia chebula Retz. Samo-thai TERMCHEB COMBRETACEAE Terminalia corticosa Pierre

ex. Laness. Tabaek-lueat TERMCORT

COMBRETACEAE Terminalia glaucifolia Craib Haen TERMGLAU


138

FAMILY GENERA SPECIES VERNACULAR CODE COMBRETACEAE Terminalia nigrovenulosa

Pierre ex. Laness.

Nam-kai TERMNIGR

MALVACEAE Thespesia lampas Dalz. & Gibs

Faai-paa THESLAMP

MELIACEAE Toona ciliata M. Roem. Mayom-hohm TOONCILI ? ? ? Ee-mann UNIDENT1 ? ? ? Ee-mann-bai-

yai UNIDENT2

? ? ? Gaam-buu UNIDENT3 ? ? ? Kra-chon UNIDENT4 ? ? ? Kruea-cha-

nuan UNIDENT5

? ? ? Kruea-ee-nuhn UNIDENT6 ? ? ? Ma-lai UNIDENT6 ? ? ? Ma-mok UNIDENT7 ? ? ? Sonn-paa-bai-

yai UNIDENT8

VERBENACEAE Vitex glabrata R. Br. Kai-nao VITEGLAB VERBENACEAE Vitex limonifolia Wall. Sawong-teen-

pet VITELIMO

VERBENACEAE Vitex pinnata Linn. Sawong-teen-nok

VITEPINN

VERBENACEAE Vitex ? Sawong VITEX1 VERBENACEAE Vitex ? Sawong-hin VITEX2 MELIACEAE Walsura villosa Wall. Kat-lin WALSVILL APOCYNACEAE Wrightia tomentosa

Roem. & Schult. Muek-man WRIGTOME

MIMOSACEAE Xylia xylocarpa Tuab. Daeng XYLIXYLO RHAMNACEAE Zizyphus cambodiana

Pierre Nam-ta-krong ZIZYCAMB

RHAMNACEAE Zizyphus oenoplia Mill. Nam-lep-yiao ZIZYOENO

Appendix

139

10.2 Growth and Yield of the permanent plots

Permanent plots PP 1-5

DBH 95 DBH 95 height height N BA Vol PLOT CODE min max min max ha ha ha

1 ANACOCCI 5.2 13.2 4.3 9.9 48 0.39 1.27 1 BAUHMONT 6.8 6.8 5.1 5.1 8 0.03 0.05 1 CASSGARR 9.6 9.6 7.9 7.9 8 0.06 0.18 1 DILLENI1 10.4 10.4 7.1 7.1 8 0.07 0.19 1 DIOSCAST 13 14.2 9.6 10.5 16 0.23 1.00 1 LANNCORO 5 13.4 3.7 8.9 40 0.24 0.77 1 MAMMSIAM 7.7 12 6.2 8.2 40 0.28 0.81 1 MITRHIRS 6 6.2 5.6 5.9 16 0.05 0.09 1 MORICORE 18.8 18.8 13.5 13.5 8 0.22 1.39 1 RANDDASY 9.4 9.6 4 7.5 32 0.22 0.54 1 SCHLOLEO 8.9 8.9 7.9 7.9 8 0.05 0.15 1 SHOROBTU 5.4 40.1 3.8 20.5 271 9.15 61.58 1 SHORSIAM 5.8 33.3 5.8 15.5 32 0.81 5.66 1 SINDSIAM 16.6 28.4 10.5 13 16 0.68 4.01 1 STERNEUR 6.9 25.4 4.3 20 88 1.22 8.03 1 TERMALAT 5.2 19.6 4.8 13 32 0.38 1.95 1 TERMCHEB 6 14.6 8.1 9.8 16 0.16 0.63 1 TERMCORT 28 28 15 15 8 0.49 3.62 1 VITEPINN 32.4 32.4 10 10 8 0.66 3.17

Total 700 15.38 95.08


2 BAUHMONT 12.1 12.1 5 5 8 0.09 0.18 2 CANASUBU 23.1 23.1 17 17 8 0.33 2.76 2 DALBCULT 7.3 7.3 7.4 7.4 8 0.03 0.09 2 GMELINA1 6.3 6.3 4.5 4.5 8 0.02 0.04 2 GMELINA2 8.7 8.7 10 10 8 0.05 0.18 2 GREWTOME 7.2 11.7 5.5 14 16 0.12 0.58 2 HALDCORD 7.3 23.4 6.7 17.5 40 0.60 4.23 2 HYMEEXCE 11.3 11.3 11 11 8 0.08 0.37 2 LANNCORO 5.8 16.3 6.1 15 159 1.65 8.48 2 PHOEPANI 10.5 14.1 11.5 15 16 0.19 1.17 2 PTERMACR 7.1 7.1 8.2 8.2 8 0.03 0.09 2 RANDDASY 5.6 6.2 6 6.8 16 0.04 0.09 2 SCHLOLEO 6.6 28.5 6.1 16 48 1.04 7.43 2 SHOROBTU 5.4 34.7 2.5 18 310 6.13 41.79 2 SHORSIAM 6 36.9 3.4 21 199 6.39 54.04


140


2 SINDSIAM 8.1 8.1 9.5 9.5 8 0.04 0.15 2 STERNEUR 11.5 11.5 10 10 8 0.08 0.34 2 TERMCORT 6.5 18.2 9.2 16.2 24 0.34 2.38 2 TERMGLAU 9.3 9.3 13 13 8 0.05 0.29 2 VITEPINN 7.3 9.5 10 11 16 0.09 0.36 2 VITEX1 9.2 13.1 11.5 14.5 40 0.42 2.48 2 WALSVILL 6.9 6.9 7.3 7.3 8 0.03 0.08 2 XYLIXYLO 8.5 18.2 10 17.3 32 0.45 2.93

Total 1,003 18.31 130.50


3 ANTIDES1 7.1 7.1 7 7 8 0.03 0.08 3 BOMBANCE 15.5 42.2 7 17.5 16 1.26 10.42 3 CANASUBU 9.6 9.6 9.3 9.3 8 0.06 0.21 3 CHUKVELU 8.4 16.1 9.5 15 24 0.29 1.71 3 DALBCAND 25.3 25.3 13 13 8 0.40 2.51 3 DALBCULT 7.6 16.3 9 15 40 0.50 2.84 3 DIOSCAST 22.7 28 16 16 16 0.81 6.38 3 GREWTOME 9.1 30.3 8.4 17 40 1.28 9.67 3 HALDCORD 5.8 6 3.7 5.3 16 0.04 0.06 3 LANNCORO 5.4 10.4 5.5 11 40 0.23 0.73 3 PAVETOME 5.3 5.3 6.5 6.5 8 0.02 0.04 3 PHOEPANI 23.4 23.4 14 14 8 0.34 2.31 3 RANDDASY 5.8 6.2 5 6.5 16 0.05 0.09 3 SCHLOLEO 6.3 21.8 7.5 14 72 0.98 5.31 3 SHOROBTU 7.1 38.8 6.5 21 103 4.78 44.91 3 SHORSIAM 5.1 41.3 5 27 318 6.16 56.25 3 SINDSIAM 24.6 24.6 13.5 13.5 8 0.38 2.46 3 SPONPINN 6.5 26.3 7 25 16 0.46 5.51 3 STERVILL 5.8 8 1.9 8.5 24 0.09 0.21 3 TERMCORT 5.5 9.6 9 11 24 0.13 0.52 3 TERMGLAU 6.7 6.7 8.2 8.2 8 0.03 0.08 3 VITELIMO 19.8 33.3 12 20 32 1.85 16.09 3 VITEPINN 6.5 37.6 9.2 18 32 1.21 9.88 3 VITEX1 5 11.1 7.1 11 32 0.19 0.75 3 VITEX2 5.3 17 9 15 24 0.23 1.43

Total 939 21.81 180.46

Appendix

141


4 BAUHMONT 6.1 6.1 5 5 8 0.02 0.04 4 CASEGREW 5.2 5.2 5 5 8 0.02 0.03 4 CASSGARR 7.8 7.8 5 5 8 0.04 0.07 4 COMBPROC 8.3 8.3 5 5 8 0.04 0.08 4 CROTOBLO 9.3 9.3 8 8 8 0.05 0.17 4 DALBCULT 15.1 17.8 12 16 16 0.34 2.25 4 DALBOLIV 7.3 33 6 17 24 0.98 7.79 4 DIOSCAST 23.3 30.2 16 20 24 1.32 11.60 4 HALDCORD 23 23 15 15 8 0.33 2.39 4 HYMEEXCE 38.3 38.3 24 24 8 0.92 11.40 4 LAGECALY 31.9 31.9 18 18 8 0.64 5.77 4 LAGELOUD 22.2 22.2 16 16 8 0.31 2.38 4 LANNCORO 6.8 23 6 18 16 0.36 2.97 4 MILILINE 5.1 17.2 6.5 14 32 0.37 2.17 4 MILLLEUC 8.5 8.5 5 5 8 0.05 0.08 4 RANDDASY 6.7 6.7 6.2 6.2 8 0.03 0.06 4 SCHLOLEO 5 54.5 5 20 103 2.61 22.73 4 SHORSIAM 65.5 65.5 26 26 8 2.68 36.66 4 SPONPINN 9.7 36.4 8 25 16 0.89 10.90 4 STERNEUR 11 11 9 9 8 0.08 0.28 4 STERVILL 36.1 36.1 19 19 8 0.81 7.90 4 TERMGLAU 23 23 22 22 8 0.33 3.60 4 TERMNIGR 16.1 37.6 2 24 40 2.27 23.99 4 VITELIMO 7.1 22.7 9.5 16 16 0.35 2.61 4 VITEPINN 9.8 52 6.2 22 48 4.39 45.08 4 VITEX2 6.9 6.9 9 9 8 0.03 0.10 4 XYLIXYLO 6.2 11 7.2 10 16 0.10 0.37

Total 477 20.36 203.43


5 DALBCULT 15.4 23.5 13 21 24 0.71 5.86 5 DIOSCAST 11 17 5 13 16 0.26 1.22 5 GARUPINN 28.7 28.7 18 18 8 0.51 4.63 5 GMELINA3 10.9 10.9 14 14 8 0.07 0.44 5 HALDCORD 9.6 62.4 9.6 29.5 24 4.09 59.03 5 LAGECALY 27.5 27.5 17 17 8 0.47 3.99 5 LAGEVILL 17.9 33.5 17 22 56 3.00 29.60 5 LANNCORO 5.3 17.6 5.5 15 24 0.23 1.42 5 MARKSTIP 6.3 6.6 5.1 5.5 16 0.05 0.09 5 MITRHIRS 7 7 6.5 6.5 8 0.03 0.07 5 PTERMACR 23.7 73.8 19 27 16 3.76 51.57 5 RANDDASY 5.2 7.2 4 7 16 0.05 0.10


142

5 SCHLOLEO 6.2 9.8 7.1 9 24 0.11 0.33 5 SHORSIAM 13 59.4 14 24 16 2.31 28.40 5 SPONPINN 8.8 8.8 7.2 7.2 8 0.05 0.13 5 STERNEUR 31.8 31.8 23 23 8 0.63 7.43 5 TERMCORT 8.2 43.7 11 23 16 1.24 14.46 5 TERMNIGR 6.3 33.7 5 25 80 3.04 31.32 5 VITEPINN 31.7 55.4 14 23 32 4.59 45.68

Total 406 25.20 285.79

2ha Permanent Plot

DBH 96 DBH 96 DBH 96 height height N BA Vol N min max min max ha ha ha 1 8.8 8.8 8.4 8.4 0.5 0.005 0.010 3 8.8 26.6 7.5 14.2 1.5 0.045 0.292 2 44.3 55.9 10 13.8 1 0.200 1.144 5 5 24.4 7.7 24.1 2.5 0.070 0.680 2 9 14.5 7.4 13.3 1 0.010 0.058 13 7.6 62.6 12.1 32.3 6.5 0.455 6.244 4 5.5 31 0 7.8 2 0.045 0.142 3 5.4 11 3.4 11.5 1.5 0.010 0.035 2 6.5 7.8 6.7 7.3 1 0.005 0.010 5 9.4 72.8 6.8 26.1 2.5 0.270 3.261 8 8.9 67.5 6 28.5 4 0.345 3.169 5 6.1 21.1 5.9 17.5 2.5 0.045 0.304 3 7.4 18.2 8.4 16.5 1.5 0.020 0.129 13 9.6 31.8 7.2 20.1 6.5 0.145 0.854 1 16.8 16.8 11.8 11.8 0.5 0.010 0.059 1 14.8 14.8 5.1 5.1 0.5 0.010 0.018 6 10.3 20.2 7.2 15.1 3 0.060 0.333 1 23.1 23.1 8.2 8.2 0.5 0.020 0.079 1 15.1 15.1 7.7 7.7 0.5 0.010 0.029 5 12.1 33.2 9.8 17.5 2.5 0.115 0.729 1 37 37 14.5 14.5 0.5 0.055 0.392 1 16.2 16.2 17.1 17.1 0.5 0.010 0.082 3 28 38.9 10.1 22.5 1.5 0.140 1.218 2 5.2 22.4 6.5 17.6 1 0.020 0.171 1 7.1 7.1 5.1 5.1 0.5 0.000 0.003 1 29.5 29.5 5.5 5.5 0.5 0.035 0.084 1 20.5 20.5 13.6 13.6 0.5 0.015 0.106 7 17.1 32.6 13.2 21.5 3.5 0.190 1.556 14 13.5 47.7 8.9 19.1 7 0.365 3.043 2 9.5 10.8 7.8 9.8 1 0.010 0.029 5 15.9 40.5 12.5 22.7 2.5 0.150 1.382

Appendix

143

DBH 96 DBH 96 DBH 96 height height N BA Vol N min max min max ha ha ha 1 8.2 8.2 9.6 9.6 0.5 0.005 0.010 12 5.3 62.3 3.5 28.1 6 0.535 6.341 11 9.4 48.9 3.2 26.5 5.5 0.440 4.685 129 7.5 65.3 5.1 30.2 64.5 5.790 60.499 12 5.6 44.3 5.4 28.4 6 0.290 2.692 12 7.7 62.5 6.2 22.5 6 0.310 2.997 3 7.5 17.6 6.1 8.5 1.5 0.015 0.057 8 5.2 34.7 3.5 18.9 4 0.105 0.744 4 7.4 28.9 5.9 23.6 2 0.045 0.432 1 8.2 8.2 5.3 5.3 0.5 0.005 0.005 3 5.1 10.5 5.5 9.5 1.5 0.010 0.032 21 5.6 27.9 3.8 23.1 10.5 0.220 1.442 1 16.3 16.3 13.1 13.1 0.5 0.010 0.062 2 8.4 19.1 7.9 12.1 1 0.015 0.089 1 39.8 39.8 22.5 22.5 0.5 0.060 0.724 1 48 48 21.5 21.5 0.5 0.090 1.012 10 7.4 78 9.5 32.8 5 1.120 16.803 3 5.8 9.5 5.9 8.1 1.5 0.010 0.023 41 5 69.9 2.8 26.2 20.5 0.710 7.568 2 35.2 57.6 21.2 29.7 1 0.180 2.573 15 9.2 58.8 13.5 30.5 7.5 0.880 11.635 9 13.6 69.4 9.8 31.5 4.5 0.535 7.035 7 9 26.8 7.1 15.9 3.5 0.080 0.513 32 5 28.8 4 24.3 16 0.230 1.314 7 5.3 9.6 5.1 9.4 3.5 0.015 0.037 21 8.7 54.1 7.3 29.1 10.5 1.035 12.080 9 12.2 42.3 9.9 28.1 4.5 0.195 2.171 92 8 53 6.5 29.5 46 2.210 23.549 23 5.3 29.3 5.1 16.1 11.5 0.230 1.148 1 40.9 40.9 15.8 15.8 0.5 0.065 0.527 1 26.5 26.5 13.7 13.7 0.5 0.030 0.184 8 8 14.1 5.2 10.9 4 0.035 0.124 1 45.2 45.2 22.4 22.4 0.5 0.080 0.935 54 5.2 65.3 4.5 26.7 27 2.280 21.039 19 5.8 75 7 29.1 9.5 0.755 6.990 9 7.9 50.1 9.5 24.7 4.5 0.250 2.659 36 5.5 57.9 3.8 26.1 18 0.770 7.128 27 5.1 41.7 5.1 26.8 13.5 0.615 6.429 385.5 23.14 239.93


144

10.3 Forest types and their distribution

Looking at mainland South-East-Asia from a phyto-geographic perspective, it could

be seen as the cross-roads in the migration of three distinct and in themselves diverse

floristic elements: The Indo-Burmese, the Indo-Chinese and the Malaysian

(ASHTON, 1995; SMITINAND et al. , 1980, 1992). As such, the number of species

found in a given area can be very high, particularly in evergreen forests.

Furthermore, local topography, edaphic and anthropogenic factors strongly influence

the occurrence, composition and structure of the different forest types. Subsequently,

a given community type might exhibit a rather diverse floristic composition in

different locations and forests of similar composition can show quite diverse

structural patterns. Finally, very different forest types can often be found in close

proximity, under apparently similar conditions, with - or without - a clear

delineation.

From a scientific perspective, vegetation classification is the attempt to find order

and hierarchies among the different types. However, even though widely applied in

temperate zones, the syntaxonomic methodology of the Zürich-Montpellier School

(BRAUN-BLANQUET, 1964) has seldom been applied in the tropics, due to the

structural and taxonomic complexity of the communities under investigation and the

lack of systematic knowledge of the flora of most areas.Tropical forest classifications

are usually based on linking physiognomic and structural characteristics of

vegetation to one or more environmental criteria, or vice-versa.

However, since classifications always have specific aims, there are many universally

applicable systems which leads to considerable confusion regarding nomenclature

(LAMPRECHT, 199O). Furthermore, with increasing local specificity and

orientation towards applied forestry, functional aspects become more and more

important. Though community structure and function are linked, structure does not

necessarily reflect function (GAJASENI and JORDAN, 1990).

Forest types and their distribution

145

Examples of classifications at the highest, global level include the climatic zoning by

HOLDRIDGE (1967) and WALTER (1971). Both link the occurrence of (usually

broadly) defined, generic - vegetation-types to a combination of temperature and

rainfall, with altitude serving as an auxiliary parameter to approximate the two. On

the other hand, classification based on life forms as defined by RAUNKIER (1937);

ELLENBERG and MÜLLER-DOMBOIS (1967) and BRÜNIG (1972) has produced

globally applicable physiognomic vegetation classification schemes. Similar

physiognomic classification schemes were devised by AUBREVILLE (1957) in

Africa.

On a more regional - or vegetation-type-specific - level various attempts have been

made to further divide the generic vegetation types and to define “forest formations”.

Examples in tropical Asia are given by WHITMORE (1984). As JORDAN (1989)

points out, the two examples also serve to highlight the subjective and somewhat

arbitrary choice of divisions. While the latter defined 15 forest formations,

WHITMORE identified only three.

A further step is the sub division of formations into forest-types and finally the sub-

division into community types. For example, within each formation identified,

WHITMORE (1984) lists several forest-types. At community level, the occurrence

of species and structural features can usually be attributed to specific site factors and

their variations. Examples of such studies in Thailand include the investigations of

BUNYAVECHEWIN (1985) and ELLIOTT (1989).

However, with increasingly finer classification grids, more diverse and functionally

different criteria can be applied. For example, a common feature of many “forest

types” in South-East-Asia is the large proportion of tree species which belong to the

DIPTEROCARPACEAE family, overall consisting of 14 genera and about 400

species (SMITINAND, 1992). In the moist evergreen forests of Kalimantan they

account for 40 to 60% of all species and in Mindanao they can reach abundance

levels of 70 to 90% (LAMPRECHT, 1990). WHITMORE, in the above example,


146

uses these taxonomic features to delineate some forest types, while others are defined

on the basis of other structural criteria.

LONGMAN and JENIK (1987) point out that more recently a renewed trend towards

phytosociological methods can be observed - a phenomenon that can probably be

attributed to the recent advancements in multivariate statistical methods (see also

JONGMAN et al., 1987; KENT and COKER, 1995).

Regional forest classifications of Asian vegetation are still missing. Most

investigations are confined to political boundaries; the area of former British India

and the states that emerged from it (TROUP, 1921; CHAMPION et al., (1936, 1965),

CHAMPION and SETH (1968); KERMODE, 1964), former Indo-China (VIDAL,

1956, 1959, 1960; ROLLET, 1972) and Thailand (SMITINAND, 1990).

Dry deciduous and savannah forests have been dealt with regionally, though only

descriptively (BLASCO, 1983; STOTT, 1976, 1984; ROLLET, 1953, ROLLET et

al., 1952). The same applies to KANJANAVANIT’s (1992) attempt to further sub-

divide deciduous forests with respect to fire susceptibility. A detailed,

methodologically defined and silviculturally relevant fine-stratification is still absent.

The aforementioned classifications may provide general information on composition,

structure and ecology of formations but they do not allow for site-specific

silvicultural decision-making, nor do they explain detailed processes except in basic

terms.The resulting information is not statistically comparable. Even though the

method is not fool proof, any initial sampling should be preceded by a study of

species composition on the basis of species area-curves to obtain information on

minimum sample areas (GAUCH, 1982; LAMPRECHT, 1990). Multi-stage

sampling is recommended for the different diameter classes under consideration.

Random plot selection, though optimal in theory, is generally unfeasible for

logistical reasons, while expert studies suffer the high risk of bias. Line sampling of

pre-stratified units appears the most sensible approach and has been used here as

described in detail before.


147

The following description of forest types of Thailand is based on SMITINAND

(1992). Additional information, when available, has been added where necessary to

enhance the description.

In the following chapters an overview of the existing forest types in Thailand will be

given, followed by a review of their utilisation in the past and at present. This will

also cover the dependencies and the influence of neighbouring countries and the

colonial powers of the past.

10.3.1 Mixed Deciduous Forests

With regard to Thailand, Mixed Deciduous Forests can be sub-divided into:

• Moist Upper Mixed Deciduous Forest

• Dry Upper Mixed Deciduous Forest

• Lower Mixed Deciduous Forest

While the first two types contain teak, the third does not. Other authors refer to these

forests as Tropical Moist Deciduous Forest (TROUP, 1921) or Seasonal Forest

(SUKWONG, 1974). The two drier types of this group are also called Tropical Dry

Deciduous Forests (FAO, 1981).

Generally, a large number of deciduous species occur, with none clearly dominant

which makes it difficult to present a composition-based description. Exceptions are

areas where Tectona grandis can exhibit its gregarious tendencies and dominate.

Such stands might conveniently be called teak forests.

10.3.1.1 Moist Upper Mixed Deciduous Forest

This forest type is also referred to as Tropical Moist Deciduous Forest (FAO, 1981).

In Thailand, it occurs between 300 to 600 m.a.s.l., usually on loamy, deep soils, both

of limestone and granite origin. The structure is three-storied:


148

• The upper layer consisting of Tectona grandis, Lagerstroemia tomentosa, L.

calyculata, Terminalia alata, T. calamansanai, T. bellerica, Afzelia xylocarpa,

Xylia kerrii, Bombax insigne, Pterocarpus macrocarpus, Dalbergia cultrata, D.

oliveri, Haldina cordifolia, Gmelia arborea, Anogeissus acuminata, Millettia

leucantha, Albizia lebbeck, A. procera, A. lebbekiodes, A. chinensis, Acacia

leucophloea, Adenanthera pavonina and Dillenia pentagyna.

• The second storey typically contains Combretum quadrangulare, Careya

arborea, Barringtonia racemosa, Millettia brandisiana, Albizia ludica, Dalbergia

ovata, D. nigrescens, Peltophorum dasyrachis, Lagerstroemia floribunda, L.

speciosa, L. macrocarpa, L. villosa, L. undulata, Diospyros mollis, D. montana,

Eugenia cumini, E. leptanthum, Vitex penduncularis, V. canescens, V. pinnata,

and Dillenia aurea

• The lowest storey is composed of Cratoxylon formosum, Mallotus philippinensis,

Gardenia coronaria, G. obtusifolia, Casearia grewiaefolia, Bauhinia racemosa,

B. malabarica, Croton oblongifolius and C. hutchinsonianum.

• Small numbers of palms, such as Phoenix humilis and some species of Calamus

occur frequently.

• Shrubs are represented by species of Croton spp., Malotus spp., Premna spp., and

Randia spp., Harrisonia perforata, Bauhinia acuminata.

• Lianas include Hymenopyramis brachiata, Congea tomentosa, Artabotrys

siamensis, Desmos spp., Bauhinia bracteata, B. scandens, Butea superba,

Spatholobus parviflorus and Dalbergia rimosa.

• The ground flora is composed of herbaceous species such as grasses of the genera

Capillipedium, Sporobolus, Themeda, Thysanolaena, Andropogon, Bothriochloa,

Saccharum, Orzya, Eragrostis, and Hyparrhenia. Others are Kaempferia,

Curcuma, Boesenbergia, Fimbristylis, Carex, Cyperus, Ceropegia, Aristolochia,

Habenaria, Peristylis, Pecteilis and Brachycorythis.


149

10.3.1.2 Dry Upper Mixed Deciduous Forest

Due to exposure, high evaporation, surface erosion and the leaching of organic

components from the soil, vegetation along ridges becomes more open. Though the

forests are still three-layered and most of the species of the Moist Upper Deciduous

forest are still present, they exhibit stunted and crooked forms. More deciduous

species like Shorea obtusa, S. siamensis, Dipterocarpus tuberculatus, D. obtusifolius

and D. intricatus begin to appear.

The ground flora is frequently destroyed by dry season fires. If fire frequency is high,

the forest may degrade into a bamboo sward, dominated by species like Bambusa

arundinacea and Thyrsostachys siamensis.

Figure 32: Mixed Deciduous Forests, picture taken during a helicopter flight in May 1997

10.3.1.3 Lower Mixed Deciduous Forest

Lower Mixed Deciduous Forest occurs in dry areas, usually between 50 to

300 m.a.s.l., with reasonably deep sandy or lateritic soils.It is structurally similar


150

to Upper Mixed Deciduous Forest, but Tectona grandis is conspiciously absent from

the canopy layer. In some situations Hopea odorata, H. ferrea and Shorea roxburghii

occur. Along rivers a “gallery forest“ version can be found, containing semi-

evergreen species like Eugenia cumini, Sapium insigne, Afzelia xylocarpa and

Dipterocarpus alatus.

10.3.2 Deciduous Forests

In areas with medium to low annual rainfall levels, pronounced dry seasons and

sandy, gravely-loam or lateritic soils, the forests become partly or even wholly

deciduous, with trees shedding their leaves during the dry season. Deciduous forests

may extend into areas where rainfall levels are higher but with extremely prolonged

dry seasons.

Primarily based on the availability of precipitation, SMITINAND (1992) has sub-

grouped deciduous forests in Thailand into

• Mixed Deciduous Forest,

• Dry Deciduous Dipterocarp Forest

• Savannah Forests.

In other classifications these forests are grouped under the heading of Tropical Semi-

Evergreen Forests (FAO, 1981).

10.3.2.1 Dry Deciduous Dipterocarp Forests

Undulating plains and ridges, low levels of rainfall, porous, heavily eroded and

leached sandy or lateritic soils of both granitic and sandstone origin and frequent

fires are the characteristics of areas in which Dry Deciduous Dipterocarp Forests

occurs.

Structurally, the forest is open and two-storied:


151

Figure 33: Cycus siamensis in a fire affected DDF stand

• The canopy-layer is predominantly composed of

xerophytic species of the DIPTEROCARPACEAE

family, hence the name. Common species include

Dipterocarpus obtusifolius, D. tuberculatus,

Shorea obtusa and S. siamensis. Sometimes

Quercus kerrii, D. intricatus, Pterocarpus

macrocarpus and Xylia xylocarpa are

interspersed.

• The lower storey is composed of shrubs like

Strychnos nux-vomica, S. nux-blanda, Dalbergia

kerrii, Symplocos cochinchinensis, Diospyros

ehretioides, Aporusa villosa, Phyllanthus emblica

and Canarium subulatum.

• The ground flora consists of species that have

distinct fire adaptation mechanisms, including under-ground tubers and the ability

to re-sprout from rootstock.

• Small bamboo species commonly found include Arundinaria pusilla, A. ciliata,

Linostoma persimilis, Enkleia malaccensis, Phoenix acaulis and Pygmaeopremna

herbacea. Other ground flora genera include Habenaria, Pecteilis, Hibiscus,

Decaschistia, Kaempferia and Curcuma. Dillenia hookeri is common, forming

clumps of low bushes.

• In areas of laterite soils often frequented by fire, Cycas siamensis (Fig. 33) occurs.

• Epiphytes are common and mostly consist of ferns belonging to the genera

Platycerium and Pyrrosia and orchids of the genera Aerides, Eria, Dendrobium,

Bulbophyllum, Cleisostoma and Ascocentrum. Dischidia rafflesiana, D. minor,

Hoya pachyclada and H. kerrii are also common.


152

Figure 34: Previously logged and fire affected DDF stand

Based on the floristic composition, BUNYAVECHEWIN (1985) has suggested a

three-class sub-division of the Dry Deciduous Dipterocarp Forests.

• Class 1 (Figure ) represents stands consisting mainly of Shorea siamensis, S.

siamensis var. tomentosa and S. obtusa.

• Class 2 is dominated by Dipterocarpus tuberculatus and D. obtusifolius with a

sub-type that also contains upper-storey bamboo.

The author points out that the class 2 community-type changes from the West to the

East of Thailand. In the West D. tuberculatus dominates (called “Kanyin“ in

Manipur in India and “Indain“ in Myanmar), in the East D. obtusifolius (“Forêt

Claire“ in French-speaking Indochina). A similar sub-division of Dry Dipterocarp

Forests has been suggested by KUTINTARA (1975).

• Class 3 is identical with the Pine-Dipterocarp association as suggested by

SMITINAND (see below). The actual species were not specified.


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KUTINTARA and BHUMPAKKAPUN (1989) noted a dwarf-variety of Dry

Deciduous Dipterocarp Forest. The validity and purpose of such a sub-classification

remains doubtful since the site investigated lies on a ridge, over granite intrusions, on

a shallow, crumbly, quartz-rich soil of low water-holding potential. More likely it is

Dry Deciduous Dipterocarp Forest as described by SMITINAND (1992), occurring

on a very marginal site.

10.3.2.2 Savannah Forests

By definition, savannah forests are characterised by grasslands where medium-height

trees are scattered, leaving an open structure. Soils are similar to those found in Dry

Dipterocarp Forests but precipitation is often as low as 500 mm per annum. Forest

fires are frequent.

Besides xerophytic tree species such as Careya arborea, Mitragyna parvifolia,

Acacia siamensis, A. catechu and Pterocarpus macrocarpus, thorny shrubs such as

Feroniella lucida and Carissa cochinchinensis are interspersed with Bambusa

arundinacea.

In the upper elevations shrubs of the genera Aporusa, Ochna and Glochidion are

frequent.

The grass layer is composed of Imperata, Vetiveria, Eulalia, Panicum, Sporobolus,

Themeda, Eriochloa and Sorghum.

In higher parts of the Thung Yai Wildlife Sanctuary in western Thailand, savannah

grasslands interspersed with Cycas siamensis are found. NAKHASATIEN and

STEWART-COX (1990) considered this a unique grassland formation rather than an

extremely fire-degraded form of Dry Dipterocarp Forest.

Savannah forests have been discussed in length by STOTT (1990) and

KANJANAVANIT (1992).


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10.3.3 Evergreen Forests

On the basis of climatic factors, SMITINAND sub-divides evergreen forests into

Tropical Rain Forests and Dry Evergreen Forests. ASHTON (1990) on the other

hand, groups them under the name Seasonal Lowland Evergreen Mixed Rain Forest.

Within this group several regional types are distinguished that partly coincide with

the classification as applied by SMITINAND (1992) for the Thai forests.

ASHTON estimates that this forest type in the past covered 1,200,000 km2 of

tropical Asia.TROUP (1921), CHAMPION (1936), SENGUPTA (1939) and

CHAMPION et al. , (1965, 1968), assert that such evergreen forests were originally

found along most of the west-facing lower mountain ranges in India and Mainland

Southeast Asia, in areas where the Southwest monsoon leads to heavy orographic

rains. It includes the western peninsular of India, the Darjeeling-Assam-Chittagong-

Arakan range, the western part of the Central Cordillera between parts of Yunnan to

northern peninsular Malaysia and reaches as far north as coastal Guanxi and Hainan.

The most common soils are yellow and red ultisols and oxisols. Evergreen forest

usually receives annual rainfall of between 1,500 and 6,000 mm, in exceptional

circumstances this may exceed 10,000 mm. Dry seasons are short. The months where

evapo-transpiration exceeds precipitation are usually five or less.

In contrast to CHAMPION (1936), ASHTON (1990) delineates these forests against

the mixed dipterocarp forests of the Sunda shelf, the Philippines and Southwest Sri

Lanka on the basis of their distinctive floristic composition, species richness and

phenology and dynamics.

In terms of composition and structure, these forests are usually multi-layered with

canopy tree heights exceeding 40 m. Species are very numerous and are chiefly or

entirely evergreen; gregariousness is strikingly absent. The forests are rich in

climbers, palms and woody and herbaceous epiphytes (TROUP, 1921).


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10.3.4 Tropical Rain Forests

Tropical Rain Forests, also known as Moist Evergreen Forest (WHITMORE, 1984)

and as Tropical Wet Evergreen Forests (CHAMPION et al. , 1968), are usually

confined to areas of rainfall above 2,500 mm per year and with a dry season not

exceeding three months. According to SMITINAND (1992), in Thailand two such

zones can be recognised, the Lower Tropical Rain Forest and the Upper Tropical

Rain Forest.

10.3.4.1 Lower Tropical Rain Forest

Usually, Lower Tropical Rain Forest occurs in areas up to 600 m.a.s.l. According to

SMITINAND, it is two-storied, but in other descriptions three-storey structures are

mentioned (e.g. WHITMORE, 1984).

• The upper layer is composed predominantly of large-sized, hygrophilous

DIPTEROCARPACEAE species of the genera Dipterocarpus, Hopea, Shorea,

Balanocarpus, Parashorea, Anisoptera and other species such as Dyera,

Endospermum, Horsfieldia, Melanorrhoea, Palaquium, Planchonella, Mangifera,

Swintonia, Ailanthus, Cedrela, Artocarpus, Bischofia, Sandoricum, Tetrameles,

Pterocymbium, Scarphium, Sterculia, Intsia, Mesua, Pterospermum. Schima,

Cinnamomum, Calophyllum, Litsea, Alstonia, Ficus, Adenanthera, Koompassia,

Lagerstroemia, Neophelium, Manglietia and Podocarpus (SMITINAND, 1992).

• The lower storey is composed of trees of medium height and diameter, including

the genera Vatica, Talauma, Baccaurea, Alchornica, Macaranga, Mallotus,

Drypetes, Cleistanthus, Glochidion, Croton, Cleidion, Antidesma, Aporosa,

Dichapetalum, Streblus, Eugenia, Phoebe, Alseodaphne, Aglaia, Garcinia,

Memecylon, Polyalthia, Mitrephora, Goniothalamus, Pseuduvaria, Orophea,

Gluta and Semecarpus

• Palms, such as Orania, Oncosperma, Calamus, Korthalsia, Daemonorops and

Licuala are abundant.


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• Vines are common such as Bauhinia, Dalbergia, Millettia, Tetrastigma,

Willughbeia, Aganosma, Poikiolospermum, Trachyspermum, Epigynum, Derris

and Entada.

• Bamboo covers disturbed areas, belonging to the genera Gigantochloa, Bambusa,

Dinochloa, Schizostachys and Dendrocalamus (SMITINAND, 1992).

10.3.4.2 Upper Tropical Rain Forest

In other classifications this forest-type is grouped under Tropical Montane and Hill

Evergreen Forest (FAO, 1981). Upper Tropical Rain Forests are found on slopes

between 600 to 1,000 m.a.s.l. and represent the transition between Lower Tropical

Rain Forest and the higher Hill Evergreen Forest (see below). In Thailand they are

usually two-storied:

• The upper storey composed of species of the genera Quercus, Lithocarpus and

Castanopsis, interspersed with members of the genera Magnolia, Michelia,

Eugenia, Pentacme, Dipterocarpus, Myristica, Canarium and Podocarpus.

• The lower storey include Antidesma, Aglaia, Baccaurea and Glochidion. Areca,

Pinanga, Calamus and Daemonorops palms are abundant.

• The undergrowth is usually dense and dominated by MELASTOMATACEAE,

ACANTHACEAE and ZINGIBERACEAE, with great numbers of terrestrial ferns

and orchids.

• Climbers are few and scattered, but epiphytes are abundant.

Trees are usually heavily covered with mosses, ferns and orchids.

10.3.5 Dry Evergreen Forest

Other authors refer to this forest-type as Seasonal Evergreen Forest

(NAKHASATIEN and STEWART-COX, 1990) and Tropical Semi-Evergreen

Forest (WHITMORE, 1984). In areas receiving 1,000-2,000 mm rainfall per annum


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this was once a wide-spread forest type that could be found all over the plains of

Thailand, but was particularly luxuriant in depressions and along the valleys of lower

hill ranges up to 500 m.a.s.l. (SMITINAND, 1977). NAKHASATIEN and

STEWART-COX (1990) quote altitudes of 800 to 1,000 m.a.s.l.

BUNYAVECHEWIN (1983) points out that it is difficult to define this forest by

elevation since it is more associated with streams rather than a particular altitude

zone. As such it might form gallery forest along streams and rivulets in areas that

receive relatively little precipitation, which could be considered an edaphic

formation.

In its structural complexity Dry Evergreen Forest can be similar to rain forest.

However, due to the agricultural potential of the mostly deep and fertile soils and the

highly valued timber of many species in this formation, in Thailand this type of

forest has disappeared in recent decades.

The forests are usually three-storied:

• The upper storey consisting of the species Anisoptera costata, Dipterocarpus

alatus, D. turbinatus, Hopea odorata, H. ferrea, Shorea thorelii, Alstonia

scholaris, Pterocymbium tinctorium, Tetrameles nudiflora, Afzelia xylocarpa,

Ailanthus triphysa, Ulmus lanceifolius, Antiaris toxicaria, Lagerstroemia

ovalifolia and Acrocarpus fraxinifolius.

• The second storey is composed of Cratoxylum maingayi, Chaetocarpus

castanicarpus, Castanopsis nepheloides, Euphorbia longana, Lithocarpus

harmandii, Spondia pinnata, Cinnamomum iners, Irvingia malayana, Vatica

cinerea, Sapium insigne and Diospyros spp.. The lower storey is dominated by the

genera Memecyclon, Cleistanthus, Aporusa, Alchornea, Baccaurea, Macaranga,

Mallotus, Knema, Melodorum, Mitrephora, Tarenna, Dillenia, Crateva and

Maerua.

• Palms of the genera Calamus, Areca, Livistona and Corypha can be found,

• Bamboo of the genera Gigantochloa, Bambusa and Dendrocalamus.


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• Lianas area abundant, belonging to the genera Bauhinia, Dalbergia, Derris,

Entada, Strychnos, Securidaca, Toddalia, Acacia, Hymenopyramis, Congea,

Sphenodesme, Uncaria, Ventilago, Tedrastigma, Artabotrys, Desmos, Uvaria and

Pisonia.

• Strangling figs are also frequent

• Epiphytes, mainly orchids and ferns, are sporadic.

• The undergrowth is dense and composed of members of the family

ZINGIBERACEAE (Curcuma, Boesenbergia, Alpinia, Catimbium, Cenolophon

and Amomum). Other genera are Tacca, Strobilanthes, Micromelum, Clausena,

Barleria, Desmodium, Moghania, Christia and Capparis and ferns of the genera

Helminthostachys, Lygodium and Thelypteris.

10.3.6 Hill Evergreen Forest

Also known as Temperate Evergreen Forest or Lower Montane Rain Forest

(WHITMORE, 1984), this forest-type occurs discontinuously in areas above 1,000

m.a.s.l., particularly in the northern highlands of Thailand. Soils are either red-

granitic, brown-black calcareous or yellow-brown sandy. Precipitation lies between

1,500 and 2,000 mm per annum, air humidity is high and temperatures are reduced

compared to the lowlands.

The forest is mostly two-storied and dominated by the genera Quercus, Castanopsis,

Magnolia, Rhododendron, laurels and teas. It is species-rich. Crown cover of the

upper canopy trees and undergrowth is dense. On moist slopes and in valleys this

forest can reach canopy heights similar to Dry Evergreen Forest, but on drier ridges

it is open-structured with heights of only 10 to 15 m (NAKHASATIEN and

STEWART-COX, 1990).

Sites investigated by SMITINAND (1992), in Thailand revealed the following

structure and composition:


159

• The upper storey is characterised by Schima wallichii, Cinnamomum spp..,

Fraxinus excelsa, Dacrydium elatum, Podocarpus imbricatus, Cephalotaxus

griffithii, Betula alnoides, Umus lancifolia, Cedrela toona, Nyssa javanica,

Quercus, Lithocarpus, Castanopsis and Calophyllum.

• The second layer is composed of Gordonia, Camellia, Pyrenaria, Acer, Careya,

Carpinus, Tristania, Sladenia celastrifolia, Notophoebe, Alseodaphne, Lindera,

Phoebe, Helicia, Macaranga, Mallotus, Rhododendron, Symplocos and Aquilaria.

• Shrubs are also abundant, belonging to the genera Daphne, Melastoma, Osbeckia,

Embelia, Maesa, Rapanea, Rhamnus, Cornus and Osyris.

• Palms are relatively few (Pinanga, Phoenix, Cycas and Gnetum).

• Herbaceous species form a rich ground flora and are represented by Catimbium,

Boesenbergia, Curcuma, Globba, Hedychium, Strobilanthes, Asystasia, Calanthe,

Malaxis, Habenaria, Anoectochilus, Anthogonium, Pollia, Streptolirium and

Ophiorrhiza. Bamboo are Teinostachys, Dinochloa, Gigantochloa and

Schizostachys. Ferns are widespread, including species of Asplenium, Leptochilus,

Polypodium, Thelypteris, Nephrolepis, Blechnum, Cyathea and Osmunda.

• Sphagnum is found in boggy areas of high altitude and sub-alpine vegetation-

types are present on summits and exposed ridges.

10.3.7 Particular Edaphic Forest Formations

Though on a regional scale a range of edaphic forest formations have been described

(see CHAMPION et al., 1965, 1968), for Thailand only three types require special

consideration.

10.3.7.1 Limestone Formations

In many parts of the country limestone ridges and cliffs can be found that contain a

specific forest community. Though its floristic composition is partly reminiscent of

Moist Upper Mixed Deciduous Forests (compare above), the community is


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strongly conditioned by the calcareous nature of the parent material. However,

despite obvious particularities, the community-type has not been studied in detail.

10.3.7.2 Freshwater Swamp Forests

Freshwater swamp forests can be found inland, along periodically or occasionally

inundated depressions. Rainfall levels usually exceed 2,000 mm per annum.

Depending on the soil-type present, distinct forest communities can be found.

On alluvial soils the ground is muddy and fen-like. Where peat deposits occur, the

ground develops into domed bogs, covered with three-storey forests:

• The upper layer is composed of large-sized trees such as Dyera costulata,

Palaquium gutta, Koompassia malaccensis, Calophyllum teysmannii and

Scaphium lychnophorum.

• The mid-storey is composed of Nephelium lappaceum, Hydnocarpus sumatranus,

Walsura trijuga, Hopea Tlatifolia, H. pierrei, Cratoxylon arborescens, Heritiera

littoralis, Ploarium alternifolium and Xanthophyllum glaucum.

• The lowest storey consists of Aglaia, Gluta, Casearia, Melaleuca leucadendra

and Alstonia spathulata.

• Ground flora is usually poorly developed and represented by Apostasia,

Boesenbergia, Hanguana, Hedychium, Costus, Bromheadia, Amischottolype,

Donax, Schumanianthus and Nepenthes.

• Palms and rattan are very common, including the genera Calamus, Korthalsia,

Plectocomia, Daemonorops, Licuala, Nenga and Pinanga, as well as Areca

triandra and Oncosperma tigillaria.

• Epiphytes are plentiful.

Where soils are sandy the structure of the forest is more open, stunted Fagaea

fragrans becomes dominant, with the bushy Baeckia frutescens and Licuala palms as

associates. Mono-specific, mono-plane stands of Melaleuca leucadendra may occur.


161

A secondary phase of this forest is called “Belukar“ in Malaysian and consists of

stunted trees and shrubs such as Melaleuca leucadendra, Eugenia grande,

Flagellaria volubilis, Derris elliptica and Spirolobium cambodianum (SMITINAND,

1992; RIELEY, 1990).

10.3.7.3 Mangrove Forests

Mangroves can be found on the estuaries of rivers and along muddy coastlines on

deep, saline alluvial deposits. Periodically inundated by tides, the semi-xerophytic

species inhabiting these zones have developed a means of storing fresh water in their

characteristically thick and leathery leaves.

The forests are zoned in relation to their proximity to the sea. Four vertically uniform

zones can be distinguished:

• The Avicennia-Sonneratia zone is the outer-most region facing the sea (Avicennia

officinalis, A. marina, Sonneratia griffithii, S. alba and S. caseolaris).

• The Rizophora zone follows with R. mucronata, R. apiculata.

• Next is the Bruguiera-Kandelia-Ceriops zone (Bruguiera parviflora, B.

caryophylloides, B. hainesii, Kandelia rheedii, Ceriops tagal and C.

roxburghiana).

• The inner-most zone consists of Lumnitzera-Xylocarpus-Bruguiera (Lumnitzera

littorea, L. racemosa, Bruguiera gymnorrhiza, B. eriopetala and Xylocarpus spp.).

• Along creeks Heritiera littoralis is common and in wind and wave-sheltered

estuaries the outermost zone is fringed by Rhizophora mucronata and R.

apiculata.

• Ground flora is always poorly developed, mostly consisting of Acanthus

ilicifolius, A. ebracteatus, Derris trifoliata, Acrostichum aureum, A. Speciosum,

Aegiceras corniculata and Scyohiphora hydrophyllacea (SMITINAND, 1992).


162

10.3.8 Coniferous Forest

Coniferous forests represent only a small proportion of the region’s forests, in

Thailand less than 2%. However, in comparison to other forest types they have

received considerable scientific attention. They are found in areas of 200 to 1,300

m.a.s.l. Rainfall levels lie between 1,000 and 1,500 mm per annum. Soils are usually

poor and acid, greyish-sandy, brownish-gravely or lateritic.

Structurally, they are two to three-storied and rather open. In areas where fires are

frequent, the forest can take on a savannah-like structure.

• The upper storey is composed of Pinus kesiya and P. merkusii. In areas where

lateritic soils occur this might also include Dipterocarpus obtusifolius and D.

tuberculatus, forming a Pinus-Dipterocarpus association.

• The second storey is composed of the regeneration of the canopy trees, combined

with Anneslea fragrans, Quercus, Lithocarpus, Castanopsis, Styrax aprica,

Myrica and Tristania rufescens.

• The lower storey is composed of small trees and tall shrubs such as Adinandra,

Embelia, Maesa, Phoenix humilis, Cycas pectinata, Vaccinum sprengelii, V.

bracteatum, Rhododendron moulmeinense, R. lyi, Baeckia frutescens and Styrax

rugosus (SMITINAND, 1992; WERNER, 1993)

Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ) GmbH

Begleitprogramm Tropenökologie (TÖB) Förderung der Tropenwaldforschung Tropical Ecology Support Program Postfach 5180 D-65726 Eschborn Federal Republic of Germany

Fax: +49-(0)6196-79-6190 E-Mail: [email protected] Website: http://www.gtz.de/toeb

Im Auftrag des Bundesministeriums für wirtschaftliche Zusammenarbeit und Entwicklung (BMZ)

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