NUTRIENT INPUTS FROM TREES VIA THROUGHFALL, STEMFLOW AND
LITTERFACL IN AN INTERCROPPING SYSTEM
A Thesis
Presented to
The Faculty of Graduate Studies
of
The University of Guelph
by
PlNG ZHANG
In partial fulfilment of requirements
for the degree of
Master of Science
July, 1999
O Ping Zhang. 1999
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NUTRIENT INPUTS FROM TREES VIA THROUGHFALL, STEMFLOW AND LllTERFALL IN AN INTERCROPPING SYSTEM
Ping Zhang University of Guelph, 1999.
Advisor: A- M- Gordon
The purpose of this study was to determine the amount of nutnent input frorn
tree rows to adjacent crops in an agroforestry intercropping system and to evaluate
the effects of those inputs on crop growth- Concentrations of N, P, K, Ca, and Mg
were rneasured in open rainfall and in throughfall, stemflow and Iitterfall from
various tree species. Average annual nutrient inputs (kg-ha-') for total-N, NO,-N.
NH,-N, Pl K. Ca and Mg were 7.49,1.04, 1.11, 2.44. 8.53, 19.09 and 4.76,
respectively. LitterfaIl frorn the plantation canopy was the major contributor of N
(90.5% of al1 nitrogen inputs), whereas throughfall contributed the most K (62.7%
of al1 potassium inputs) and stemflow accounted for a very small proportion of the
nutrients but contributed the most P (50.3% of al1 phosphorus inputs). Wheat growth
response showed that the average wheat yield within 1 m of the tree row was 1-6
times the yield at a distance of 6m from the tree row.
ACKNOWLEDGEMENTS
I would like to thank the members of my advisory cornmittee. Dr. Paul
Voroney, Dr. Victor R. Timrner and especially my advisor. Dr. Andrew M. Gordon,
for this opportunity to pursue graduate research. Thank you for ail of the insightful
discussions, guidance, advice, encouragement and continued support. 1 would also
like to thank the Ontario Ministry of Agriculture and Rural Affairs for providing
financial support-
I would like to acknowledge the efforts of sevzral my dear friends - Dr.
Naresh Thevathasan for helping me settle down and for technical advice, especially
regarding laboratory equipment and field protocols. Ms. Elaine Mallory for
encouragement, friendship and proof-reading and Mr. Jamie Simpson for statistical
assistance.
To al1 of my friends, CO-workers and members of the Agroforestry Research
Group (especially Rick Gray, Nancy Luckai, Gordon Price, Rob McCart. Allison
Back, Kelly Bowen, Glen Wilson, Maren Oelbermann, Shelly Hunt, Heather
Middleton, Sandra Cook and lan Short), I extend my overall appreciation and
gratitude. Thank you for giving me strength and courage, for always being there,
for understanding and supporting me and for providing continual help.
I also wish to express gratitude to my parents for their continued love, for
their encouragement of me to work hard to achieve my goals, as well as for
providing unconditional help when I encountered difficulties during my study.
Finally, to al1 who helped me improve my English during the course of my
study - thanks!
All of you have helped make rny dream a reality!
TABLE OF CONTENTS
ACKNOWLEDGEMENTS
TABLE OF CONTENTS
LIST OF TABLES
LIST OF FIGURES
LIST OF APPENDICES
1. INTRODUCTION AND LITERATURE REWEW
1-1 Introduction
1-2 Literature review 1 -2.1 Agroforestry and intercropping 1.2.2 Nutrient inputs via throughfall. stemflow. litterfall and
dry deposition
2. MATERIALS AND METHODS
2.1 Site description
2.2 Field experirnental design
2.3 Sample collection and preparation 2.3.1 Throughfall 2.3.2 StemfIow 2-3.3 Rainfall 2.3.4 LitterfaIl 2.3.5 Soil nitrogen 2.3.6 Wheat biomass. grain yield and average tillers per plant
2.4 Laboratory analysis 2.4.1 Water 2.4.2 Soil 2.4.3 Plant
2.5 Statistical analysis
3. RESULTS AND DISCUSSION
3.1 LitterfaIl nutrient inputs
3.2 Throughfall nutrient inputs
3.3 Sternflow nutrient inputs
3.4 Nutrient inputs and wheat growth response under tree rows 3-4.1 Nutrient inputs 3.4.2 Wheat growth response
4- CONCLUSIONS
6. APPENDICES
Appendix 1. Seasonal patterns of throughfall for various nutrients in an intercropping system in Southern Ontario. Canada 1997-1 998.
Appendix 2. Seasonal patterns of stemflow for various nutrients in an intercropping system in Southern Ontario. Canada 1997-1 998-
Appendix 3. Modelling nutrient inputs in an intercropping situation in Southern Ontario, Canada,
LIST OF TABLES
Table 1.1. Comparison of macronutrients in stemflow in various forests.
Table 1.2. Cornparison of macronutrients in throughfall in various forests.
Table 1.3. Macronutrient concentrations of the foliage of 15 species of broad-leaved deciduous trees in the Lake Opinicon area of southeastern Ontario (from Ricklefs. 1982).
Table 1.4. Quantities of rnacronutrients in aboveground litterfall in various forests (from Kimmins. 1997).
Table 1.5. Nutrient concentrations of foliar elements in a variety of forest stands.
Table 3.1. Annual Iittërfall biomass distribution by different distances from tree rows under different tree species in the intercropping system. 38
Table 3.2, Nutrient concentrations in the litterfall from different tree species in the intercropping system. 39
Table 3.3. Estimated quantities of annual nutrients returned to ground by litterfall of different tree species in the intercropping system. 41
Table 3.4. Average concentrations of various nutrients in the throughfall from different tree species in the intercropping system. 43
Table 3.5. Estimated quantities of nutrients annually returned to the ground by net throughfall from different tree species in the intercropping system.
Table 3.6. Nutrient concentrations in the sternflow from different
tree species in the intercropping system- 48
Table 3.7. Estimated quantities of nutrients annually returned to the ground by net stemflow from different tree species in the intercropping system. 50
Table 3.8. Annuai nutrient input (kg-ha-') by litterfall, net throughfall and net stemflow in the intercropping systern, 52
Table 3.9. Comparison of nutrient concentrations in 0-20cm soi1 layer at diflerent distances from tree rows under different tree species in the intercropping system. 54
Table 3.10. Estirnated quantities of soi1 nutrient contents (kg-ha") in 0-20cm soi1 layer in different distances from tree rows under different tree species in the intercropping system. 55
Table 3.1 1. Wheat growth response (tillers-plant-') at different distances from tree rows under different tree species in the intercropping system. 57
Table 3.12. Wheat biomass (kg-ha-') at different distances from tree rows under different tree species in thtt intercropping system. 59
Table 3.1 3. Wheat yield (kg-ha-') at different distances from tree rows under different tree species in the intercropping system. 61
Table 3.14. Average total nitrogen concentrations of wheat grain (% dry weight) at different distances from tree rows under different tree species in the intercropping system. 62
Table 3.1 5. Estimated total nitrogen contents of wheat grain (kg-ha-') at different distances from tree rows under different tree species in the intercropping system .
LlST OF FIGURES
Figure 2.1: Field expefimental design used to rneasure throughfall, stemfiow, Iitterfall. soi1 and crop parameters. The design was repeated for 5 tree species. using 5 replications over two years. 30
LlST OF APPENDICES
Appendix 1. Seasonal patterns of throughfall for various nutrients in an intercropping system in Southern Ontario, Canada 1997-1 998.
Appendix 2. Seasonal patterns of stemfiow for various nutrients in an intercropping systern in Southern Ontario, Canada 1997-1 998.
Appendix 3. Modelling nutrient inputs in an intercropping situation in Southern Ontario, Canada-
1. INTRODUCTION AND LITERATURE REVIEW
1 -1 Introduction
This thesis is an investigation of nutrient inputs from trees via throughfall.
stemflow and [itterfall in a temperate intercropping system. The experirnent was
conducted under black walnut (Juglans nigra L), red oak (Quercus mbra L.). silver
maple (Acer sacchannum L.), hybrid poplar (Populus deltoidesxnigra DN 177) and
white ash (Fraxinus amencana L.) plantings with associated crops rotated in corn
(Zea mays L. cv. Pioneer 3917). soybean (Glycine max L.) and winter wheat
(Tntcum aestivum L.). The study was carried out over two field seasons (1 997 and
1998) in a replicated 10-1 2 year old tree intercropped planting at the University of
Guelph Agroforestry Research Station. It is an important component of a larger
investigation of intercropping systems in southern Ontario. Canada.
The hypothesis being examined is that additional nutrients from tree Iitterfall,
throughfall and stemflow may become available to the adjacent crop in addition to
becoming added to the soi1 nutrient pool. In other words, crops among trees rows
might enjoy enhanced nutrient inputs from trees, and may therefore be nutritionally
better than crops grown in a monocropping situation. The research provides
essential data for the management of fertilizer applied to row crops in intercropping
systems. The full use of fertilization via litterfall, throughfall and stemflow can be
achieved by reducing the use of chemical fertilizer, thus protecting the environment
as well as lowering production costs.
To maximize these benefits, an understanding of the complex biological and
ecological interactions that occtir in intercropping systems is currently of the utmost
importance. However, Iittle research on interactions between trees and crops with
respect to nutrient regimes has been conducted in intercropping systems, and
consequently, this study was designed to assess the role of throughfall. sternflow
and Iitterfall in transporthg nutrients from tree rows to adjacent crops and to quantify
these nutrient input fluxes.
1.2 Literature iieview
1 -2.1 Agroforestry and Intercropping
Agroforestry is an integrated land-use management system for production
and farmland conservation. The International Councii for Research in Agroforestry
(ICRAF) has defined agroforestry as "a sustainable management system for land
which increases overall production, combines agricultural crops. tree crops and
forest plants andfor animals simultaneously or sequentially on the sarne unit of land,
and applies management practices which are compatible with the cultural patterns
of the local population" (King. 1979). Based on this definition, there has been a long
history of agroforestry in the temperate zones of the United States and Canada,
Australia and New Zealand, Europe, including the Soviet Union and China.
Windbreaks and silvopastoral systems are the two major types of agroforestry most
commonly utilized in the temperate zone. although there has also been some
interest in systems where trees and crops are integrated (Byington, 1990). Such
integrated systems bridge production agriculture and natural resource conservation
with environmental protection and human needs.
In North America. agroforestry practices include integrated riparian
management systems, silvopastoral (tree-animal) systems. windbreaks and
shelterbelts, alley or intercropping systems, and forest farming (natural
forest/specialty crop). Benefits often attributed to the adaption of agroforestry are
increased crop production, diversified local economies, improved water quality. soi1
erosion and sediment control, filtering and biodegradation of excess nutrients and
pesticides, reduced flood damage, microclimate moderation, and diversified habitats
for wildlife and humans (Gold, 1995). Agroforestry practices can also be used to
protect the quality of the environment by reducing on site degradation processes
and by buffering adjacent areas from the negative impacts of activities in those
areas (Williams, 1993). For example, forest plantations can be used to rehabilitate
degraded fields by reducing soi1 erosion, and improving soi1 organic matter. nutrient
status, and soi1 structure. When planted as a buffer or contour strip, trees can trap
sediment (Williams, 1993). reduce runoff and nutrients in groundwater (Correll,
1983; Daniels and Gilliam, 1996), and shade waterways (Gordon and Kaushik,
1987). Through the selection of the proper species and the application of good
management strategies, increased financial gain can also be realized.
lntercropping or alley-cropping consists of planting trees at spacings that
allow the cultivation of crops among them. In temperate systems, the trees are
usually planted in widely-spaced rows leaving a stnp or "al1eyJy between the rows for
crop production (Gordon and Newman, 1997). lntercropping and related cover
cropping practices have been used to establish forest plantations and to re-
establish natural forest cover in agricultural areas (IMlliams and Gordon. 1992). The
complex interactions among the crop and tree components demands that systems
must be designed carefully so that the plantations will provide the expected benefits
(Gordon and Newman, 1997).
Black walnut is one tree species that has been commonly used in
intercropping systems in North America. Wth this tree species many landowners in
the eastern United States and Canada have adopted a spacing of 12.5m between
tree rows and 3m between trees within rows (270 trees-ha-' ) (Garrett et al.. 1991).
The selection of companion crops is also a critical decision in the design of an
intercroppinglalley-cropping system. At wider spacings, annual crops can be grown
for a number of years. followed by perennial crops such as hay (or pasture) or other
more shade tolerant crops (Gordon and Newman, 1997).
In the tropics. agroforestry. especially fortns involving intercropping, is often
cited as an excellent land-use system because of its productivity. sustainability and
adoptability (Nair. 1993), and many ecological interactions in these tropical systems
have been researched (e.g. Tian. 1992). In temperate systems. much of the early
research on intercropping systems has been concerned with establishment and
4
cultural practices (Gordon and Williams, 1991). More recently. research has been
conducted on the developing interactions found in temperate systems as the trees
age. For exarnple, Williams and Gordon (1995) studied soi1 water potential. soi1 and
air temperature, relative humidity, wind speed and light regimes in clean-weeded
tree rows within crops of corn, soybeans and winter wheat. The growVi patterns of
these crops are different and this ultimately affected environmental and
microclimate conditions within the tree rows and the actual growth of the trees.
Thevathasan and Gordon (1995). working in southern Ontario with a potted poplar-
barley systern, found no difference in the final grain yield (or in other parameters)
between monocropped and intercropped barley. This suggested that poplar was
not in cornpetition for moisture or nitrogen with the barley, and was actually
exploiting a different set of soil resource "horizons". Furthemore, total above ground
biomass produced per pot in the intercropped system was 14% higher than in the
monocropped system.
This study led to further investigations in the field. partially reported on by
Thevathasan and Gordon (1997). The authors investigated soil nitrogen
mineralization and respiration fluxes at regular time and space intervals in the crop
alley-way between adjacent rows of poplar trees in an intercropped field. There was
an increase in N avaiiabiiity due to enhanced N mineralization close to the tree row.
thought to be a result of poplar leaf biomass inputs from shedding trees in the fall.
resulting in a corresponding increase in barley grain N concentration. It was also
noted that there was an increase in the release of CO, from the soi1 profile adjacent
5
to the tree rows as cornpared with the middle of the alley. This was presumably a
result of enhanced root and rnicrobial respiration. Mclean (1990) modelled light
penetration into tree (black walnut and red oak) rows established with corn. and
su bsequent seedling carbon assimilation. He was able to demonstrate differences
in assimilation (initiation and duration) and in the height growth of seedlings,
depending upon the orientation of the rows of corn. Ntayombya and Gordon (1995).
working in southern Ontario with a potted black locust (Robinia pseudoacacia L.)
and barley (Hordeum vulgare, var. OAC Kippen) system, found that intercropping
decreased yiefds of the cornpanion crop. However. they also noted that cultural
practices such as pruning and mulching could moderate yield reductions. In
addition. they found the overall productivity of the black locust-barley system to be
53% higher than that of the sole cropped barley. They were also able to
demonstrate a transfer of nitrogen from the black locust to the barley: barley in the
intercropped treatments showed superior quality and had, on average. 23% higher
grain nitrogen content than sole-cropped barley.
Rhoades et al. (1998) indicate that on highly-weathered Uitisols of the
Georgia (USA) Piedmont, a combination of no-till agriculture and alley cropping
presents an option for rapidly increasing soi1 nitrogen availability while restoring
long-term soi1 fertility. Averaged over a Cmonth study. soi1 nitrate and ammonium
were 2.8 and 1.4 times higher in the alley-cropped than in the treeless no-till plots.
Alley cropping with Albizia (Albizia julibnssin L.) hedges offen Piedmont farmers an
option for reducing reliance upon chemical N fertilizer while improving soi1 organic
6
matter levels. Thevathasan (1 998) has also indicated that intercropping may be one
way in which to reduce N-loadings to adjacent water ways. His prelirninary rnodels
indicate a 50% reduction in N-loadings, largely attributable to the adoption of
intercrop ping practices.
Buresh and Tian (1 998). working in sub-Saharan Africa with trees to improve
soils, found that trees can influence both the supply and availability of nutrients in
the soil. Trees increase the supply of nutrients within the rooting zone of crops
through (1) input of N by biological N,fixation, (2) retrieval of nutrients from below
the rooting zone of crops and (3) reduction in nutrient losses from processes such
as leaching and erosion. Trees can increase the availability of nutrients through
increased release of nutrients from soi1 organic matter (SOM) and recycled organic
residues,
To summarize, agroforestry systems. in addition to providing crop and
income diversification strategies, are often utilized on degraded lands for their soil,
water and nutrient conservation properties (Young, 1989). This is especially true in
the tropics (e.g. Grewal et al., 1994). In contrast, in temperate North America,
agroforestry systems have developed largely as a result of financial considerations,
most likely because the adoption of agroforestry by the farming community is
econornically driven. For example, Ball (1991) working in southern Ontario,
advocated the adoption of nut production and hard wood intercropping as a
potential diversification strategy for tobacco farmers faced with dwindling incomes
from that crop. Nonetheless, there are many conservation and environmental
benefits (e-g. maintenance or enhancement of biological diversity) associated with
the development and adoption of agroforestry systems in North Arnerica, and
recently, some of these benefits have been evaluated in tandem with economic
returns (e-g. Simpson et al., 1994).
1.2.2 Nutrient inputs via throughfall. stemflow. litterfa11 and dry deposition
LitterfaIl. throughfall and stemfiow are the three main pathways through
which nutrients move from trees to surrounding components of the ecosystern. In
intercropping systems, they may also serve as a source of nutrient input to crops
grown adjacent to tree rows. In this section. the major characteristics of these fluxes
and associated pools are discussed -
Stemflow
Stemflow is defined as the concentration of precipitation by leaves and
branches into flow pathways down the stem. Precipitation that reaches the soi1 via
a plant stem (Kimmins, 1997). In north temperate systems. stemflow is a function
of stand density, canopy size. precipitation regime, bark roughness, canopy holding
capacity and other factors. (Kimmins. 1997; Perry, 1 994; Voigt, 1960).
The absolute amount of interception loss is relatively independent of storm
size since it is determined by interception storage capacity, which is more or less
constant. By the same argument, interception loss becomes a decreasing
percentage of total precipitation as storm size increases. Interception storage for
8
tree and shrub cover has been reported to range between 0.25 and 7.6 mm of rain
and up to 2.5 cm (water equivalent) of snow (Satteriund. 1972). Interception loss of
rain attributed to trees can range from 100% for light summer showers in dry
climates to 0% for heavy or continuous winter rain in humid climates. It is much
reduced in deciduous trees in the nonleafy period.
Water intercepted by tree crowns is redistributed into two major subtypes and
reaches the fioor very non-uniformly: throughfall and stemflow. The importance of
sternflow varies greatly. Immature forests, forests of hardwoods such as cherry
(Prunus spp. L.) or alder (Alnus mbra Bong. ; Alnus sinuata (Rage) Rydd.). and
forests of coniferous species such as pine (Pinus spp.) tend to have more stemflow
because their upturned branches act as a funnel. Stemflow also varies with stand
density. For exarnp le, an 1 8-year-old Doug las-fir (Pseudotsuga menziesii (Mirb)
Franco.) spacing plantation near Vancouver. B.C. (Kimmins, unpublished data).
revealed that interception loss varied from 15 to 26% of incident precipitation as the
number of trees per hectare decreased from about 10.000 to 730, and that the
relative proportions of stemfiow to throughfall declined from 44% (Le. 44% of the
water reaching the ground beneath the trees was sternflow) in the most dense stand
to 3% in the least dense stand. This difference was attributed to differences in
crown morphology.
Tree species with pendulous branches tend to have little stemflow and
redistribute much of the incident precipitation into canopy-edge drip. Species with
erect or acute-angled branches have much more stemflow and less canopy drip.
9
The closer the spacing in many stands. the higher the proportion of acute-angled
branches and the greater the importance of stemflow (Kimmins. 1987). Stemfiow
is also affected by bark roughness. Smooth-barked species have little stem water
storage capacity. and stemflow will commence on smooth-barked species such as
beech (Fagus grandifolia Ehrh.) after only slightly more than 1 mm of rain has fallen
(Voigt, 2 960; Leonard, 1961). Rough-barked species such as spruce (e-g. Picea
spp.) and other conifers often have a rarge stem storage capacity, and appreciable
stemflow rnay not reach the ground until more than 2 cm of rain has fallen (Helvey
and Patric, 1965; Chourmouzis, 1995). The amount of water arriving via stemflow
per unit area over a small area close to the tree bases has been found to be up to
seven times that of the incident precipitation (Gersper and Holowaychuk. 1970).
Quantitative contributions of stemflow to overall nutrient cycling are srnall
and often limited to small distances (about 30cm) from the tree base (Voigt. 1960a;
Cole et al., 1967; Mahendrappa and Ogden 1973b). although the overall effects of
stemfiow can be significant in some circumstances (Mina, 1965; 1967). Where
stemflow is appreciable, it serves to concentrate a lot of the incident precipitation
close to the base of the trees. For example, in a study of the distribution of
radioactive fall-out in the soi1 beneath beech trees in Ohio, it was found that soi1 at
the base of a tree where there was abundant stemflow contained five times as
much radioactivity as soi1 where there was no stemflow.
Acidified stemflow of some tree species has lowered soi1 pH around tree
stem (Matsura et al., 1991). and the stemflow pH of urban street trees has been
10
found to be higher than that of some suburban trees. One of the possible reasons
for higher pH is neutralization by higher concentrations of K', Ca2+ and ~ g ~ ' in the
stemfiow (Takagi et al., 1997). It has also been suggested that the quality and
quantity of stemfiow and throug hfall from individual trees can also influence soi1
properties (Zinke, 1962).
Many researchen have quantified nutrient additions and changes in nutrient
concentrations in stemflow (Cole et al.. 1967; Carlisle et al.. 1967; Duvigneaud and
Denaeyer-DeSmet, 1970; Eaton et al.. 1973; Mahendrappa. 1974; Malkonen,l974;
Torrenneva, 1975; Verry and Timmons, 1 976; Tang, 1 996; Li et al.. 1 997; Whifford
et al., 1997; Takagi et al., 1997; Oyarzun et al., 1998). However, there is still a great
need for information on the chernical composition of stemfiow from different tree
species in Canada and their influence on the soi1 properties (Foster and Gessel.
1 972).
Sternflow has been shown to contribute 0.0-1 -1 kg - ha-'- yrl N, 0.0-0.1 kg
- ha-'- yr-' P, 0.2-7.2 kg ha-'- yfl K, 0.4-6.2 kg - ha*'- yrl Ca. and 0.24.8 kg - ha-'.
yr-' Mg in nutrient returns to various forest types (Table 1.1 ) (Kirnmins, 1 997).
There appear to be no reports concerning the chemistry of sternflow in
intercropping systems.
Throug hfall
Throughfall is defined as precipitation that either falls to the soi1 surface
directly through gaps in the canopy, or drips from branches and foliage (Kirnrnins.
11
1997). In north temperate systerns, throughfall is a function of stand density, canopy
size, precipitation, holding capacity and many other factors (Kimmins, 1997; Perry,
1994)-
The nutrient content of throughfall rnay either decrease or increase on its
way through the canopy. Decreases reflect direct absorption by foliage or foliar
epiphytes (including lichens, fungi. and bacteria). However, increases are more
commonly reported than decreases and result from: a. nutrients that have collected
on foliage through dryfall, and b. nutrients leaching from foliage or foliar epiphytes.
The former is an input to the system, while the latter is part of the intrasystem cycle.
It is very difficult to distinguish between these two sources (Perry, 1 994).
Temperate and tropical forests growing on relatively fertile soils mostly add
nutrients to precipitation. Forests g rowing on highly infertile soils, however, often
scrounge cations and phosphorus (the most Iimiting nutrients in many tropical
systems) from rainfall as it passes through the canopy (Duvignead and DeSmet,
1 970; Jordon et al.. 1982; Brasell and Sinclair, 1983).
Any nutrient may be leached from tree canopies by rainfall as long as it is in
soluble form. However, the basic cations are usually more prevalent in throughfall
than nitrogen and phosphorus. This is particularly true for potassium. which is not
known to occur in organic forms within tissues (Duvignead and DeSmet, 1970;
Jordon et al., 1982; Brasell and Sinclair, 1983). The potassium content of
precipitation is often increased 10-fold by passage through the canopy
(Gooley, 1983).
lntracycle nutnents in throughfall may corne primarily from canopy
components other than leaves. Reiners and Olsen (1 984), for example. studied
nutrient fluxes to and from various parts of balsam fir (Abies balsamea (L.) Mill.)
canopies and found that dead twigs and lichens growing on twigs added well more
than 10 times the amounts of sulfate and potassium to precipitation water than were
added by foliage. On the other hand. lichens were a strong sink for ammonium and
nitrate in precipitation. Active nutrient release by dead twigs to precipitation water
may explain why calcium, which is quite immobile in living tissues, sometimes
occurs in rather high concentrations in throughfall.
Throughfall is a major component of nutrient input and cycling in forest
ecosysterns. Many researches have quantified nutrient additions and changes in
nutrient concentrations in throughfall as a result of passage through forest canopies
(Nye, 1961 ; Attiwill, 1966; Carlisle et al., 1965,1967; Brown et al-, 1 970; Denaeyer-
DeSmet, 1 970; Wells et al., 1972; Reiners, 1972; Abee and Lavender, 1 972; Hart
et al., 1973; Eaton et al., i 973; Malkonen, 1974; Torrenneva, 1975; Henderson,
1977; McColl et al., 1978; Sigmon et al., 1989; Arthur, 1992; Blew et al., 1993;
Matzner et al., 1994; Amezaga et al., 1996; Fenn et al., 1997; Lin et al., 1997), and
much attention is being focused on the extemal and interna1 sources of throughfall
enrichment (Parker, 1983). Throughfall deposition collection rernains a useful tool
for quantiQing the input of elements from atmospheric deposition to the forest soi1
(Hovrnand et al., 1995; Butler et al., 1995).
Throug hfall has been shown to contribute 0.9-1 1 .O kg - ha-'= yrl N, 0.3-2.7
14
kg - ha-'- y s P. 4.1-1 96.0 kg - ha-'- yr-' K. 2.0-26.0 kg - ha-'- yr-' Ca, 0.4-16.0 kg
ha-'- yr' Mg in nutrient returns to various forests types (Table 1.2) (Kirnmins. 1997).
There appear to be no reports concerning the chemistry of the throughfall in
intercropping systems.
Litterfal l
Litterfall is defined as Ieaves. branches and bark that are annually shed from
trees. Litterfall studies have largely focused on aboveground litterfall processes,
although the few data that are available suggest that in most forest ecosystemç. the
death of roots and mycorrhiza may account for two thirds or more of the narogen
returned to the soi1 in plant litter (Cole and Rapp, 1981 ; Vogt et al-, 1986).
The return of nutrients frorn the tree component of the forest to the soi1
provides an important source of nutrients for replenishing the soi1 and ensuring
availability for further plant developrnent. Litterfail from the forest canopy is often the
major contributor of N to the soi1 system (e.g. Foster. 1972) but is also important
as the source of the majorÏty of the nutrients taken up annually by plants (e-g. P. Ca.
Mg). Decomposing Iitter forms a superficial organic layer that plays an important
role in the protection of soi1 against erosion and in regulating soi1 moisture status
(Kimrnins. 1997). Litterfall generally accounts for the majority of the nitrogen,
calcium, and magnesium loss from standing vegetation. and leaching generally
accounts for the majority of the potassium loss. The major pathway of phosphorus
loss is occasionally Iitterfall and sometimes leaching (Kimmins. 1997).
15
The litterfall component of the nutrient cycle has been studied in many
conifer and hardwood forests (e.g. Madgwick and Ovington, 1959; Will, 1959; Nye.
1961 ; Ovington, 1962; Bray et al., 1964; Carlisle et al., 1966. 1967; Cole et al..
1967; Durigneaud and Denaeyer-DeSmet. 1970; Hegyi, 1972; Gosz et al., 1972;
Foster and Gessel. 1 972; Abee and Lavender, 1 972; Nihlgard. 1972; Foster. 1 972.
1 974, Morrison, 1973, 1974; Malkonen, 1974; Ashton, 1975; Attiwill, 1978; Lee,
1978; Binkley, 1982; Baker. 1983; Nair. 1984; Sharrna. 1989: Zhang. 1990;
Crockford et al., 1 997; Santamaria, 1998; Crockford et al-. 1998).
Table 1.3 and Table 1.4 present a summary of the quantities of selected
rnacronutrients transferred from trees to soi1 by aboveground litterfall. The quantity
is a function of the biomass, the type (leaves, branches. bark. etc.), and the nutrient
concentrations in the litterfall , al1 of which Vary from site to site. Litterfall losses are
generally greatest on moist, warm. fertile, and other high-productivity sites and least
on dry, cold, infertile, and other low-productivity sites.
Litterfall has been shown to contribute 11-228 kg - ha4- yr ' N; 0.2-9.0
kg ha-'. yrl P; 2.5-103 kg - ha-'- yrl K; 7-0-206 kg - ha". yrl Ca; 1.145 kg ha"-
yfl Mg in nutrient retums to various forest types (Table 1.3) (Ricklefs et al.. 1982).
(Table 1 -4) (Kimmins, 1 997)-
Wth the exception of Thevathasan and Gordon (1 997). who studied litterfall
-N inputs in a poplar-barley system, there appear to be no reports concerning the
chemistry of litterfall in intercropping systems.
Table 1.3. Macronutrient concentrations of the foliage of 15 species of broad- leaved deciduous trees in the Lake Opinicon area of southeastern Ontario (from Ricklefs, 1982).
Macronutrient concentrations (percent dry weight) Species N P K Ca Mg Fag aceae
Fagus grandifolia 2- 1 (beech) 1.9
1-8 Quercus alba L- 2.2
(white oak) 1-9 1-8
Quercus ruba 1.8 (red oak) 1 -8
1.8 Quercus marcrocarpa Michx. 2.1
(bur oak) 2-1 2.1
Aceraceae Acer negundo L- 2.5
(Manitoba maple) 2.7 2-4
Acer pensylvanicum L. 1.9 (striped map le) 1 -6
1.3 Acer rubrum L- 2-0
(red maple) 1.5 1.4
Acer saccharum Marsh. 2.2 (sugar maple) 1.5
1 -7 Oleaceae
Fraxinus amencana 2.1 (white ash) 1-9
1 -6 Fraxinus nigra Ma rs h . 2- 1
(black ash) 2- 1 1.7
Fraxinus pennsylvanica Marsh. 1 -8 (red ash) 1.8
1 -4
Table 1.3, (Continued).
Species Macronutrient concentrations (percent dry weight)
N P K Ca Mg - - - -
Saliaceae Populus balsamifera L. 2-0 0.29 0-88 0-75 0-32
(balsam poplar) 1 -9 0.29 0.73 0.84 0-25 1 -6 0.20 0-51 0-65 0-24
Populus deltoïdes Bartr. 2-4 0.23 1.19 0-70 0-17 (eastern cotton wood) 2.3 0.19 0.44 0.92 0.20
1 -9 0.14 1-36 0.86 0-20 Pop ulus grandiden tata M ic hx- 2-5 0.24 4-36 0.86 0.20
(big-toothed aspen) 2-4 0.18 0-59 0.70 0.30 2.2 0.18 0-49 0-62 0-22
Populus tremuloides Michx, 2.6 0.24 0-61 0-54 0-19 (trembling aspen) 2- 1 0-17 0-76 0-83 0-26
2- 1 0.17 0.63 0-94 0-26
Table 1 -4. Quantities of rnacronutrients in aboveground litterfail in various forests (from Kimrnins, 1 997).
N P K Ca Mg Location (kg-ha-'-yP') Reference
2-5 7.8 - Malkonen, - 1974 Scots pine, Finland
Doug las-fir, Washington
Jack pine, Ontario
Canada
Douglas-fir, Oregon
Nothofagus forest.
New Zealand
Oak forest, England
Oak forest, Belgium
Spruce, U S S R -
Hardwood forest, N.H-
Loblolly pine, N.C.
Oak forest, U.S.S.R.
Birch forest, U.S.S.R.
Beech, Sweden
Red alder, B.C. Canada
Tropical forest, Ghana
Cole et ai-, 1967
Foster and Gessei,
1972
Abee and Lavender,
1972
Ovington, 1 962
Carlisle et al., 1966
Duvigneaud and
Denaeyer-DeSmet,
1970 -
Ovington, 1962
Gosz et al-, 1972
Ovington, 1962
Ovington, 1 962
Ovington, 1 962
Nihlgard. 1972
Binkley, 1 982
Nye, 1961
Leaves are the major component of aboveground Iitterfall in most
ecosystems (Kimmins, 1997). and the nutritional status of tree leaves provides an
important diagnostic tool for establishing their condition (Innes, 1993; Wyttenbach
et al., 1995). While most studies have concentrated on identifying deficiencies.
excesses may also occur, particularly with nitrogen, sulphur and some heavy metals
(Bergman, 1993; Breckle et al., 1992). Major problems occur when comparing foliar
nutrient concentrations in trees in different areas and through tirne because of the
spatial and temporal variation of nutrient concentrations (Helmisaari, 1990: Santene
et al., 1990)- ln addition, the nutritional status of forest trees has only been
established for some species and the nutrient dynamics of other tree species
remain virtually unknown (Santamaria and Martin, 1998).
A summary of the variation in foliar nutrient concentrations in some tree
species is given in Table 1 -5. Over a two year period (1 992-1 993), foliage samples
from different tree specks were taken in 17 forest stands located in Navarre. Spain.
Samples were analysed for Ca, Cd, Cu, Fe, K, Mg, Mn, N, Na, P. Pb, S. and Zn.
The health of the sampled trees was also assessed by determining the degree of
defoliation and discolouration of the canopies (Santarnaria and Martin, 1998).
Strong relationships between f~ l i a r nutrient concentration and stand
productivity have been reported for various tree species (Van Cleve et al.. 1983;
Allen and Gillespie, 1991). These relationships are of great importance in
quantifying canopy-scale processes on a landscape level. For example, canopy
nitrogen (N) content has been shown to be correlated with aboveground net primary
31
Table 1.5. Nutrient concentrations of foliar elernents in a variety of forest stands (after Santarnaria and Martin, 1 998). - Macroelements (rngag'l) @ Microelements (vg#gs1)
Stand Species Ca K Mg N P S Cd Cu Fe Mn Na Pb Zn 1 Quercusrobur 12,3 13,6 2.1 26,9 25 2,4 0,05 10.0 163 977 491 1.5 27 2 llexaquifolium 13,O 153 2,7 29,O 2.2 1.7 0.24 6,9 81 983 127 0,8 104
3 Quercusrobur 17.3 9,3 2.5 19.1 2.5 2,3 0,05 8.6 143 622 224 1,3 16 4, Fagus sylvatica
8 5 ~ a g u s sy~vatica 6 Fagus sylvatica 7 Pinus sylvestris 8 Qther deciduous* 9 Pinus sylvestris 1 O Fagus sylvatica 11 Fagus sylvatica 12 Quercus ilex 1 3 Quercus ilex 14 Pinus sylvestris 15 Quercus faginea 16 Pinus nigra 8 5 6,O 1.8 12,3 2,l 1.2 0,04 4,6 30 31 17 0,7 26 17 Quercus ilex 20,O 6.8 1,7 17.0 2.0 1.8 0.06 6,5 137 181 77 1.0 22
* Acer Campestre, Corylus avellana and Fraxinus excelsior
productivity across a variety of coniferous and deciduous forests (Birk and Vtousek.
1986; Matson et al., 1994). This relationship is not surprising considering that foliar
nutrients. particularly N and P. influence the photosynthetic capacity of leaves and
thereby overall canopy photosynthesis (Linder and Rook. 1984; Field and Mooney,
1986; Foyer and Spencer. 1986). However, the strength of the relationship varies
depending on whether a mass or area-based expression (either nutrients or
photosynthesis) is utilized (Reich and Walters, 1994; Reich et al., 1995). The
photosynthetic capacity of leaves and canopies normally changes along gradients
of varying resource (light, water, and nutrients) availability (Field, 1991). and this
has been associated mainly with changes in canopy specific leaf area (SLA, Leaf
area per unit mass) (Gutschick and Wiegel. 1988; Brand. 1987; Running et al.,
1986). Many researchers have reported on the relationship between nutrient
concentration and growth response for various tree species (Grier et al., 1981 ; Van
Cleve et al., 1983; Pastor et al., 1984; Bowen et al.. 1984; Waring et al.. 1985;
Mclaughlin et al.. 1985; Nambiar et al., 1987; Mitchell, 1 990: lngested et al.. 1991;
Slapokas et al., 1991), but Iittle, if any information exists on the crop growth
response or productivity under plantations in intercropping systems.
Dry Deposition
Nutrients contained in dust and gases that are present on leaf surface are
solubilized and become part of throughfall. A heterogeneous mixture of gases and
aerosols are either raked from horizontally moving air masses by the canopy or (in
the case of large aerosols) seffle ont0 canopy surfaces under the influence of
gravity. Collectively referred to as dry deposition, these represent a significant
pathway by which nutrients and other elements are added to local ecosystems. In
forests that are periodically immersed in clouds or fog, elements are additionally
deposited on canopy surfaces along with water droplet (Perry, 1994)-
Dryfall is used to describe the transfer of atmospheric gases and dust to
surfaces. such as tree crowns which very effectively remove gases and dust from
atrnosphere. This is both good news and bad news for trees. Dryfall rnay provide
an important source of nutrients, but in the industrial northern hemisphere, an
increasing proportion of dryfall over the past few decades has been pollutants
(Perry, 1 994).
In areas with polluted air or high levels of atmospheric dust from natural
sources (e.g. sites that are downwind from deserts or agricultural lands). significant
amounts of some elements are added to ecosystems through dry deposition. In
addition to gases, nutrients are input from the atrnosphere to forests as constituents
of aerosols, particles ranging from 5 mm to 20 prn in size. At least 77 different
elernents have been detected in atmospheric dust, including al1 of the essential
plant and animal nutrients. (Bowen (1 979) presents data on the aerosol composition
of the atmosphere at various points across the globe). Aerosols are readily washed
out of the atmosphere by precipitation and may also be deposited on canopy
surfaces by condensation.
Much of the atmospheric input of sulfur and nitrogen (excluding the biological
fixation of N2) is derived from gases- nitrogen frorn nitrous oxides and ammonia. and
sulfur from sulfur dioxide. These react chernically with foliar or soi1 surfaces in a
process that is greatly facilitated if the gases are dissolved in water. Nitrogen and
sulfur are transferred from the atmosphere to foliar surfaces with particular
efficiency in forests that are frequently enshrouded in clouds or fog (Lovett et al.,
1982) and from the atrnosphere to surface soi1 layers when they are wet
(Hanawalt 1969a. 1969b). Malo and Purvis (1964) estimated that 20-60 kg - ha-'-
yr ' of nitrogen were absorbed as ammonia (NH,) in the New Jersey soils they
studied and Young (1964) similarly found that NH, was absorbed in Pacific
Northwest soils-
These values do not represent a net nitrogen increment to the ecosystem,
since NH, is also released frorn canopies and soils to the atmosphere. Whether a
given forest (or any vegetation type) absorbs more NH, than it releases or vice
versa, depends at least in part on atmospheric concentrations of the element.
Recent work by Langford and Fehsenfeld (1 992) in the rnontane forests of Colorado
shows that when atrnospheric NH, concentrations were low, forest canopies
released more NH, to the atmosphere than they took up. When atmospheric
concentrations were high. net transfer was in the opposite direction (Le. from the
atmosphere to forest). In some areas, atmospheric concentrations rnay be high
enough to produce net transfer to forests only when winds were from agricultural
areas. Since NH, is volatilized from animal wastes and fertilizers, agriculture is
believed to be a significant source of NH, and acid rain in Europe.
25
Calcium. potassium, and rnagnesium are major constituents of dry deposition
in both temperate and tropical forests (Jordan, 1982; Swank and Henderson,
1976;Ulrich et al., 1981). Between 1969 and 1972 in one German beech forest, the
proportion of total atmospheric inputs accounted for by dryfall ranged from 0% for
phosphorus to 78% for potassium and 89% for manganese (Ulrich et al., 1981).
Proportions of dry input for the other nutrients were generally on the order of 30%
to 50%. ln contrast. dry deposition accounted for 20% of the atmospheric
phosphorus inputs to a Caribbean pine forest in Belize but only 8% and 9% of the
potassium and calcium, respectively (Kellman and Carty. 1986).
Nutrients deposited on canopies may be absorbed before they are washed
to the ground (particularly elements that are in short supply). In a mixed hardwood
forest in the eastem United States, dry deposition was estimated to account for 56%
of the total atmospheric inputs of sulfate and inorganic nitrogen (Le., nitrate and
amrnonia). 59% of the potassium, and 67% of the calcium (Lindberg et al., 1986).
In that study, 7% of the deposited nitrogen was retained in the canopy, probably
absorbed directly by foliage or epiphytes growing on the foliage. Most of the acidity
(Le., H' ions) accompanying the nitric and sulfuric acids that composed a high
proportion of the dry deposition to that site were also absorbed by foliage with an
accompanying release of calcium and potassium ions from foliage. Direct
absorption of nutrients by leaves and canopy epiphytes has been shown to be quite
important on nutrient-poor sites in Amazonia (Jordan et al., 1979).
In summary. the amount of nutrients added to ecosystems from the
26
atmosphere is extremely difficult to measure accurately. particularly in areas that
are impacted by acid rain. Most available data on atmospheric inputs are based on
the nutrient content of bulk precipitation, and do not account for deposition on
canopy and soi1 surfaces. Such values probably underestimate total atmospheric
inputs by 10% to 90% depending on the nutrient in question and the local
ecosystem. The difficulty of rnaking accurate measurements is fu rther compounded
by the fact that in at least some ecosystems, significant amounts of nutrients are
directly absorbed by canopies and hence never appear in collectors on the ground.
On the other hand, many of the nutrients that are captured in collectors placed
beneath canopies do not represent inputs from the atmosphere but rather are
leached from foliage. Leaching of cations from foliage occurs in al1 forests, but is
particularly prevalent in areas with acid rain (Perry, 1994).
2. MATERIALS AND METHODS
2.1 Site Description
The study was conducted at the University of Guelph Agroforestry Research
Station in southern Ontario (43' 16' 30" N. 8 9 O 26' 35" W), at an elevation of 340rn.
Mean annual precipitation at this site is 702mrn. The mean frost free period is 136
days and the mean annual temperature is 6.65OC with average highest
temperatures of 25.5OC in July and average lowest temperatures of -12.2% in
January. The temperature extremes range from -33OC to 38OC. The soi1 type is
sandy loam (Luvisolic order, grey brown luvisols great group, Can. Syst. Soil Class..
1974) with A-horizon depths between 28 and 53cm. All cultural practices (land
preparation, seed rate, weed control and fertilizer application) were the same for
al1 growing seasons in the overall study. The land was zero-tilled. During the study
period the field was fertilized at the rate of 45 kg N ha" during the last week of April.
The site was used for continuous hay production prior to the initiation of the
overall intercropping study in 1987. Annual crop production prior to this time had
been in decline and soi1 erosion was becoming a serious problern. The first tree
planting was established in 1987 with row spacings of 12.5m and 15.0m. parallel to
the crop rows, and within row spacings of 5m and 6.25m. Trees were lower stem-
pruned on an ad hoc basis during the initial years.
Since 1990, three annuai crops have been grown under normal rotation
between the tree rows at the site: corn. soybean and winter wheat. The main tree
species at the study site hclude black walnut, hybrid poplar, silver maple. red
maple, red oak, white ash, Nonnray spnice (Picea abies (L.) Karst.) and eastern
white cedar (Thuja occidentalis L.).
2.2 Field Experimental Design
The current experiment was conducted in an intercropped field with wheat-
tree, and soybean-tree combinations at the Agroforestry Research Station. Guelph.
Treatments included five tree species - black walnut, red oak, hybrid poplar, white
ash and silver maple. Five trees were randomly selected (within existing designs)
for each tree species (total 25 trees) for throughfall and stemfiow collection. At each
tree. three sampling plots were established at distances of lm, 3.5m and 6m from
the tree row for the collection of soil, Iitterfall and crop (wheat) biomass and yield
data. The data was collected over two years (1 997. 1998). Data was analysed as
a 3 (distance from tree row) x 5 (species) factorial design. The layout of the
experiment is shown in Figure 2.1.
2.3 Sample Collection and Preparation
2.3.1 Throug hfall
Throughfall was collected from beneath the overhanging tree canopy and
removed within 24 hours of the end of each rainfall event from July to November
29
*w O min gauges
tree row
and stemflow samplers
6m )/sampiing points
- litterfail, soi1
and crop parameters
Figure 2.1. Field experimental design used to measure throughfall, stemflow. litterfall, soi1 and crop parameters. The design was repeated for 5 tree species, using 5 replications over two years.
1997 (14 rainfall events), and from May to June 1998 (6 rainfall events) using 25
throughfall collection gauges (5 species x 5 replications). 50ml water was collected
for each of 25 samples fiom each rainfall event. The pH and volume of each sarnple
were detemined on site using a Digi-Sense Model 5985-80 pH meter and
volumetric cylinder respectively. Residual water was poured around the tree base
after each measuring and sarnpling. By the end of the 1997 sampling season.
snowfall had comrnenced and 50 to 100% of the leaves had been shed from the five
identified tree species. Sarnples were placed in a cooler box with ice. transferred
to the lab and stored at -20% in the dark until analysed for nutrient content.
Throughfall collectors consisted of rnodified Plastmo K-snap eaves trough,
lOcm in width and 75cm ni length with a catchment ares of 750cm2. Polyethylene
tubing connected the troughs to 5-10 litre jugs, depending on species of the
sarnpled trees; nylon screening was also inserted into the link between the tubing
and trough in order to prevent the entiy of foreign matter. The throughfall collectors
were mounted on frarnes (about 0.5m in height) and inclined gently to the tubing
end. After each sampling, collectors and screening rolls were cleaned using water.
2.3.2. Stemflow
Stemflow was intercepted using spiral collars of spl iit vinyl tubing and grav ity
fed through intact tubing into plastic receptacles at the base of the trees after each
rainfall event A total of 25 trees received collas. The height of the lower end of the
collar varied from 0.3-0.5m above ground level, depending on the shape of the tree
base. To ensure total stemflow interception an adhesive (Silicone II) was used to
seal the coliar to the stem- 50mf water was collected for each of 25 samples from
each rainfall event. Nylon screening was also inserted into the link between the
collar and receptacle in order to prevent the entry of foreign matter. The pH and
volume of each stemfiow sample was deterrnined on site using a Digi-Sense Model
5985-80 pH rneter and volumetric cylinder respectively and then the rest of the
water was poured around the tree base. Stemflow samplings were conducted at the
same time as throughfall collection. The samples were placed in a cooler box with
ice, transferred to the lab and stored at -20°C in the dark until analysed.
2.3.3. Rainfall
Rainfall was collected after each rainfall event using four funnel-type
collectors that were constructed using 5-litre bottles with a 140crnZ catch area
plastic funnel fitted to the top of the bottle. A nylon screen roll was inserted in the
connecting stem between funnel and bottle to prevent foreign matter (leaves, insect
frass, etc.) from entering. The funnel-bottles were then attached on raised stands
(1 -5m) and placed in an open area away from any obvious influence of canopies of
trees and crops. Precipitation sarnplings (four at each collection) were conducted
at the same time as stemflow and throughfall. The sarnples were placed in a cooler
box with ice, transferred to the lab and stored at -20°C in the dark until analysed-
2.3.4. LitterfaIl
Leaf biomass distribution on the study site was assessed at 3 distances (1 m.
3.5m and 6m) from the 25 sarnpling trees by setting up 75 litterfall traps. These
were located on the northeastern side of the tree rows due to the prevailing wind
direction. The traps were 2m in length paralleling tree row and l m in width, the
boundary which closed to the tree row was 1.0m from the tree row. They were fixed
on the ground using stakes; Iitterfall collected in traps was removed by hand so that
the sarnples rernained intact prior to analysis- LitterfaIl collections began at the
beginning of leaf shedding in later September and conti~ued to the end of shedding
in early December 1997. In order to avoid decay of the shed leaves, the collections
were conducted once or twice a week depending upon the humidity and
temperature between collection periods-
The samples from each trap were air dried, mixed completely, and then
stored in open-top paper bags. Samples were then placed into the drying oven for
48 hours at 65*C, dried, and then weighed for biomass. About 209 litterfall from
each sample was taken and ground in a Wiley miIl for nutrient analysis.
2.3.5 Soil nitrogen
Total nitrogen: About 100-2009 of field moist soi1 for each of 75 samples was
collected from a depth of 0-20cm on July 16, 1997 at 3 distances, 1 m. 3.5m and
6m, from 25 sampling trees. The soi1 was air dried and woody debris were removed
by hand. Air dried soi1 samples were then ground in a grinder and sieved through
a 2mrn screen. The samples were placed in the drying oven for 48 hrs at 65OC
33
before digestion.
lnorganic nitrogen: About 100 to 2009 of field moist soi1 for each sample was
collected from a depth of 0-20cm at the same locations as for total nitrogen
sarnpling. Sampling was on a monthly basis starting in June and ending in August
1998. Soil sampling was collected hnro days after a substantial rainfall event. Soil
was mixed well and free of any woody debris. Soil samples were placed in a cooler
box with ice, transferred to the lab and kept frozen at -20°C until extraction for NO,-
N and NH,-N.
2.3.6 Wheat biomass, grain yield, and average tillers per plant
Total above ground wheat biomass, grain yield and average tillers per plant
were assessed several days before crops were harvested. Data were collected in
both 1997 and 1998-
From the same locations where Iitterfall and soi1 samples were collected,
wheat plants (including roots) were removed within a sample area of 2m by 0.2m.
A total of 75 samples were collected. After the number of plants and the tillers per
plant were counted, wheat roots were removed and then samples were placed in
paper bags and dried in a drying oven at 60-70°C for 2-4 days. Dried samples were
weighed for biomass. Grain was shelled and weighed for yield. Appraximately 209
of grain was ground for nutrient analysis.
2.4 Laboratory Analysis
2.4.1 Water
Throughfall, stemflow and rainfall samples were thawed and filtered through
Whatman No.2 filter paper before analysis. N and P concentrations were
determined using a Technicon Autoanalyzer II Systern, and K, Ca and Mg were
determined using fiame analysis on a Varian Spectra AA-300 Atomic Absorption
Spectrorneter (Va rian Associates, Sunnyvale, CA).
2-4-2 Soil
1) Total nitrogen
Soil and grain samples were digested using the Kjeldahl Method and then
total nitrogen was analysed using a Technicon Autoanalyzer II System (Technicon
Industrial System, Tarrytown, N.Y.).
2) Inorganic nitrogen (NO,-N and NH,-N)
Samples were allowed to thaw in order to re-incorporate the moisture inside
the bags before extraction with 2N KCI. 209 of soi1 was extracted with 60ml of 2N
KCI in a 100ml clear snap via1 by shaking on a mechanical shaker for one hour
(Keeney and Nelson, 1982). In order to determine the moisture content of the
samples, another sub-sample of soi1 was taken from each sample and oven-dried
at 105°C for 48 to 72 hours. The calculated moisture contents were then used to
35
convert ppm nitrate to a dry soi1 weight basis (pgll00g soil). Extracts were analysed
on a Technicon Autoanalyzer II system.
2.4.3 Plant
Total nitrogen on litterfaIl and wheat grain was done using standard Kjeldahl
methods and then analysed using a Technicon Autoanalyzer II System.
Total P, K, Ca and Mg were done using the Dry Ash digestion rnethod
(Gavlak, 1997) and then analysed using a Technicon Autoanalyzer II system for P
and flame analysis on a Varian Spectra AA-300 Atomic Absorption Spectrometer
for K, Ca and Mg,
2.5 Statistical Analysis
Statistical analysis was conducted using SPSS 7.5 for Windows (General
Linear Model-General Factorial, Normal probability plots, Data transformations, etc.)
and Microsoft Excel 7.0 for Windows 95 (data organization, graphie).
3. RESULTS AND DISCUSSION
3.1 LitterfaIl nutrient inputs
The annual Iitterfall biomass (g-m-2) distribution at different distances frorn
the tree rows under different tree species in the studied intercropping system is
shown in Table 3.1. The Iitterfall biornass from different tree species is significantly
different at pl; 0.05: silver maple = hybrid poplar > red oak = white ash > black
walnut.
For al1 species, litterfall biomass between 1.0m to 2.0m from the tree row was
greater than litterfall at a distance of 6.0m to 7.0m. For walnut. this difference was
5.66 times, for red oak, 3.1 1 times, for silver maple, 2.93 times, for Hybrid poplar.
2.07 times, for white ash, 12-68 times.
Some between species differences were also apparent. For example.
regardless of distance from tree row, litterfall (g-m-2) was always greatest under
silver maple and hybrid poplar compared to the other species. The lowest litterfall
was found under black walnut,
The mean concentrations of the major elements in the Iitter are shown in
Table 3.2. Leaves from black walnut and silver maple had the highest litterfall N
concentration. For P. K, Ca and Mg, no obvious trends were found with 4 of the 5
species (not the same ones) exhibiting similar leaf nutrient concentrations.
Table 3.1. Annual litterfall biornass (g~rn'~) distributions by different distances from tree rows under different tree species in the intercropping system.
LitterfaIl biomass (gm2 I SD) in distances from tree rows
Btack walnut 24.261 4.05 a (a) 8.5512.79 a (b) 4.2910.58 a (b)
Red oak 1 07.27121.86 b (a) 46.9511 3.17 b (b) 34,4714.47 b (b)
Silver maple 191,47132.57 c (a) 99.89118.90 c (b) 65.40114.68 c (b)
Hybrid poplar 161.4718.95 c (a) 105.77113.12 c (b) 78.0215.63 c (c)
White ash 113,58129.46 b (a) 40.5914.94 b (b) 8.9611.69 a (c)
Values followed by the sarne letter by column across species and (row) across distances are not significantly different at ps0.05.
Table 3.2. Nnutrient concentrations in the litterfaII from different tree species in the intercropping system -
Concentrations of nutrients (% dry weight * SD) Species
N P K Ca Mg Black walnut 1,401 0.121 O -405 2-466 0.61 5
10,079 a k0.007 a *O-034 ab i0-076 a 10.070 a
Red oak 0-740 0.056 0-297 1,735 0-520 i0-077 b *O-015 b 10.043 a k0.325 abc 10.126 a
Silver rnaple 1-286 0.084 0-264 1,305 0.21 0 10,131 ac 10.047 ab 10.155 a 0,731 b *O-121 b
Hybrid poplar 0.956 0.093 0-476 2-469 0.631 k0.077 d *O-009 ab 10.056 b 0-396 ac 10-052 a
White ash 0.896 0.094 0-341 2,459 O -442 10.123 bd IO-012 ab 10-045 ab *O-18lac 10,109 a
Values followed by the same letter. by colurnn. are not significantly different at ps0.05.
The estimated quantities of annual nutrients returned to the ground by Iitterfall of
different tree species are given in Table 3.3.
For al1 species, nutrient inputs within 1.0m to 2.0m from the tree row were
greater than the inputs at a distance of 6.0m to 7.0m except the nutrients of P. K.
Ca, Mg from silver maple. N: for walnut, this difference was 5.65 times, for red oak,
3.1 0 times, for silver maple, 2.92 times. for hybrid poplar. 2.04 times, for white ash.
12.73 times; P: for walnut, this difference was 5.80 times, for red oak, 3-21 times,
for hybrid poplar, 2.07 times, for white ash. 13.25 times; K: for walnut. this difference
was 5.76 times, for red oak, 3.1 5 times, for hybrid poplar, 2.07 times, for white ash.
12.39 times; Ca: for walnut, this difference was 5.65 times, for red oak, 3.16 times,
for hybrid poplar, 2.07 times, for white ash, 12.64 times; Mg: for walnut, this
difference was 5.76 times, for red oak, 3.17 times, for hybrid poplar, 2.07 tirnes. for
white ash, 12.00 times.
LittefiaIl frorn the trees in the intercropping system was a major contributor
of N but was also important as a source of nutrients taken up annually by plants,
e-g. Ca. Silver maple transferred the maximum N (1 5.2 kg-ha-') to the soil, followed
by hybrid poplar (1 1.0 kg-ha-'), white ash (4.86 kg-ha-'), red oak (4.62 kg-ha-'), black
walnut (1.74 kg-ha-'). Hybrid poplar transferred the most Ca (28.5 kg-ha-') followed
by silver maple (15.5 kg-ha-'), white ash (1 3.4 kgeha-'), red oak (1 1.1 kg-ha-'), and
black walnut (3.08 kg-ha-'). The magnesium content of Iitterfall ranged from 7.27
kg-ha-' for hybrid poplar to 2.37 kgaha-' for white ash. The potassium content of
litterfall ranged from 5.49 kg=ha-' for hybrid poplar to 0.50 kg-ha-' for black walnut.
40
Table 3.3. Estimated quantities of annual nutrients returned to the ground by litterfall of different tree species at different distances from the tree row in the intercropping systern.
Returned Black walnut Red oak Silver rnaple Hybrid poplar White ash nutrients (kg-ha- ) content mean conteniTëK content mean content mean' content mean
Values followed by the same letter by column across distances for the same nutrient element or by (row) across species are not significantly different at p i 0.05.
The phosphorus content of litterfall ranged from 1.06 kg9ha-l for hybrid poplar to
0.1 5 kg-ha" for black walnut (Table 3.3)-
The results from the intercropping situation can be compared to nutrient inputs
by Iitterfall under various forest types. The annual nutrient inputs by litterfall for N,
P. K. Ca and Mg were 34.0, 2.0, 16.0, 45.0 and 8.0 kg-ha", respectively in a
Quercus pinus (L.) forest (Henderson. 1977) and the annual nutrient inputs by
litterfall for N, NO,-N+NH,-N, K, Ca and Mg were 9.0. 1 -0. 8.0, 0.9 and 1 -4 kg-ha-'.
respectively, in an Eucalypt (Eucalyptus spp. Benth. & Hook.) plantation (Crockford,
1998). The nitrogen content of Iitterfall ranged from 41 kg-ha-' for an E. Regnans
forest (Ashton, 1975) to 9.8 kg-ha-' for an E. Obliqua/baxten (L' Herit.) forest (Lee
and Correll. 1 978). while the Ca of those forests were 48.8 kg-ha" for E. Regnans
and 17.1 kg-ha-' for E. Obliquahaxten. The inputs of phosphorus were 0.33 kgoha-'
and 1.9 kg-ha", respectively. Annual nitrogen inputs as high as 200 kg-ha-' have
also been reported by Nye (1971) for a moist tropical forest in Ghana with an
associated phosphorus input of 7.3 kg-ha". A comprehensive list of nutrient input
as litterfall by various forest types has been presented by Bevege (1 978). LitterfaIl
inputs under intercropping are lower than those in mature forest types. most likely
as a result of the lower tree density in the intercropped situation.
3.2 Throug hfall nutrient inputs
The average concentrations (mg-L-') of nutrients in the throughfall from different
tree species in the intercropping system and in rainfall are shown in Table 3.4.
42
Table 3.4. Average concentrations of various nutrients in the throughfall from different tree species in the intercropping system.
Concentrations of nutrients (mgC1 * SD) Species NOrN NH,-N P K Ca Mg Black walnut 0.6610.88 a 0.0810.17 a 0.68î1.48 a 5.3215.37 a 4.3613.08 a 1 Jïîl .O2 a
8 Red oak 1 ,09&1. 18 b 1.1713.38 b 0.7711.56 a 3.3712.75 a 3.9912.66 a 1.2310.65 b Silver maple l.8OIl.34 c 2.3418.79 c 0.4110.61 b 3.8611.83 a 4.8311.61 a 1.52kO.4Iab
hybrid poplar 1 XkO.88 bc 0.48k0.96 d 0.5111.25 b 7.9817.89 b 5.1211.70 b 1.57M.48ab
White ash 0,9510.88ab 0.2010.47a 0.4711.16b 3.4111.86a 4.5512,41a ll.42IQ.58ab
Values followed by the same letter by column across species are not significantly different at ps 0.05.
Silver rnaple exhibited the highest throughfall NO,-N and NHhN concentrations. For
KI Ca and Mg, throughfall concentrations aiways exceeded those in rainfall,
regardless of tree species. Little difference was noted between tree species.
although throughfall from hybrid poplar was higher than the other species for K and
Ca. Forthe N species and P, throughfall concentrations occasionally equalled those
found in rainfall. For example, P throughfall concentrations under black walnut and
red oak were higher than those found in rainfall, although throughfall P
concentrations under silver maple. hybrid poplar and white ash did not significantly
differ from those in rainfall-
Estirnated quantities of nutrients annually returned to the ground by net
throughfall from different tree species at the intercropping system are shown in
Table 3.5. Throughfall from the intercropped plantation canopy was a major
contributor of K and Ca. The net throughfall of hybrid poplar in the studied
intercropping field exhibited the maximum potassium inputs (1 5.44 kg-ha-'). followed
by silver maple (7.67 kg-ha.'), black walnut (2.99 kg-ha-'), white ash (1 -62 kg-ha-')
and red oak (1 -29 kg-ha-'). The calcium inputs of net throughfall ranged from 8.99
kg-ha-' for hybrid poplar followed by 8.93 for silver maple, to 1 -39 kg-ha" for red oak
and the net throug hfall of silver maple transferred the most NOrN and NH,Nl (2.73
and 3.05 kg-ha'' respectively), followed by hybrid poplar (1 -75 and 0.73 ), red oak
(0.24 and 0.34), white ash (0.32 and 0.10). black walnut (0.06 and 0.09). The
phosphorus inputs of net throughfall ranged from 0.38 kg-ha-' for hybrid poplar to
0.04 kg-ha-' for white ash and the magnesium content of net throughfall ranged
44
Table 3.5. Estimated quantities of nutrients annually returned to the ground by net throug hfall from different tree species at the intercropping system.
Nutrïents returned to ground (kg-ha-'-yr')
Species NO,-N NH,-N P K Ca Mg Black wainut 0-06 a 0-09 a 0-17 a 2-99 a 2.21 a 0.92 a
Red oak 0.24 b 0-34 b 0-14 a 1-29 a 1.39 a 0-42 a
Silver maple 2-73 c 3-05 c 0.12 a 7-67 b 8.93 b 2-77 b
Hybrid poplar 1.75 d 0-73 b 0.38 b 15.44 c 8.99 b 2-71 b
White ash 0-32 b 0-10 a 0-04 c 1-62 a 2.02 a 0.62 a -- - -
Net throughfall (kg-ha-') = throughfall (kg-ha-') - rainfall (kg-ha-'). Values followed by the same letter by column are not significantly different at ps 0.05.
from 2.77 kg-ha-' for silver maple to 0.42 kg-ha-' for red oak (Table 3.5). In short.
the silver maple and hybrid poplar, with the exception of P returns under silver
rnaple, retumed the highest nutrient contents of N, P. K, Ca and Mg from throughfall
to the surrounding intercropping system.
The results from the intercropping situation can be compared with nutrient
inputs from net throughfall under variouç forest types. The annual nutrient inputs by
throughfall for N. P. K. Ca and Mg were 2.9, 0.3, 16.7, 12.4 and 1.9 kg-ha-',
respectively in a Quercus prinus forest (Henderson, 1977). The annual nutrient
inputs in throughfall for N, NO,-N+NH,-N, K. Ca and Mg were 9.0. 1.0. 8.0, 0.9 and
1.4 kg-ha-'. respectively in an Eucalypt plantation (Crockford, 1998). and the annual
nutrient inputs in throughfall for N, P. K. Ca and Mg were 10.60, 0.63. 26.94. 6.98
and 1,98 kg-ha", respectively in a northern hardwood forest (Eaton. 1 973).
3.3 Sternflow nutrient inputs
The average concentrations (mg-L-') of nutrients in stemflow from different
tree species in the intercropping system and nutrient concentrations in rainfall are
shown in Table 3.6. For al1 nutrient elements, stemflow concentrations aiways
exceeded (ps 0.05) those in rainfall, regardless of tree species. Stemflow under
silver maple generally contained the highest concentrations of nitrate and
ammonium, with nitrate stemflow of silver maple = hybrid poplar whereas the
stemfiow under black walnut contained the highest concentrations of calcium and
magnesium. For phosphorus, stemflow concentrations under al1 five tree species
46
did not significantly differ from one another, although the concentrations were higher
than those found in rainfall. For magnesium. stemflow concentrations under four
tree species other than black walnut did not significantly differ from one another. For
P, K, Ca and Mg, respectively. stemflow concentrations from silver maple, hybrid
poplar and white ash were similar.
Estimated quantities of nutrients annually returned to the ground by net
sternflow from different tree species in the intercropping system are shown in Table
3.7. Stemflow from plantation canopies accounted for a very small proportion of
total nutrients added although P contributions were significant. The maximum
stemflow phosphorus flux was found associated with silver maple (4.10 kg-ha*'),
followed by 3.56 kg-ha-' for hybrïd poplar, 0.32 kg-ha-' for black walnut, 0.24 kg-ha-'
for white ash, and 0.13 kg-ha-' for red oak.
Except for NH,-N returns under hybrid poplar, al1 the nutrient elements,
NO,N, NH,-Nt Pl K, Ca and Mg fluxes under silver maple and hybrid poplar were
found to be higher than other tree species within the five studied tree species. The
NO,-N and NH,-N flux of net stemflow ranged from 0.05 and 1.20 kg-ha-',
respectively for silver maple to 0.01 and 0.004, respectively for black walnut. The
potassium flux of net stemflow ranged from 0.29 kg-ha-' for hybrid poplar to 0.08
kg-ha" for white ash, red oak and black walnut The calcium content of net stemflow
ranged from 0.1 2 kg-ha-' for silver maple to 0.04 kg-ha-' for white ash. The
magnesium content of net stemflow ranged from 0.05 kgoha-' for hybrid poplar to
Table 3.6. Nutrient concentrations in the stemflow from different tree species in the intercropping system.
Species NO,-N NH,-N P K Ca Mg (mg-L-' I SD)
Bfack walnut
Red oak
Silver maple
Hybrid poplar
White ash
Rainfall 0.51 0-08 0-45 0.22 O -60 0.21 10.56 d iO.12d k1.28 b 10-09 c 10-18 d 10.09 c
Values followed by the same letter by column are not significantly different at ps 0.05.
0.01 kg-ha-' for red oak and white ash. Except for hybrid poplar NH,-N, silver maple
and hybrid poplar retumed the highest NI P. K, Ca and Mg, respectively to the soi1
within the five studied tree species-
The results from the studied intercropping system can be compared with the
inputs of nutrients via net stemflow under various forest types. The annual nutrient
inputs by stemflow for N, K. Ca and Mg were 0.16. 2.22, 0.32 and 0.08 kgoha-'.
respectively in a red rnaple (Acer mbwm) plantation (Mahendrappa, 1974). The
annual nutrient inputs by stemflow for N, NO,-N + NH,-N. K. Ca and Mg were 0.6.
0.2, 1.5.0.2 and 0.3 kg-ha-', respectively in an eucalypt plantation (Crockford, 1998)
and the annual nutrient inputs by stemflow for N, P, K. Ca and Mg were 1.1 1, 0.1 0,
3.51. 0.64 and 0.19 kg-ha-'. respectively in a northern hardwood forest (Eaton.
1973).
3.4 Nutrient inputs and wheat growth response under tree rows
3.4.1 Nutrient inputs
As shown in the previous section, nutrient inputs from trees in an
intercropped situation rnay be substantial. The nutrients from throughfall and
sternflow will be imrnediately available to adjacent crop plants whereas the nutrients
in litterfaIl will only become available gradually, as the rate of release will depend
Table 3.7. Estimated quantities of nutrients annually returned to the ground by net stemfiow from different tree species in the intercropping systern-
Nutrients in stemflow returned to soi1 (kg-ha"-yf')
species NO,-N NH,-N P K Ca Mg BIack walnut 0-01 a 0-004a 0.32a 0-08 a 0.06 a 0-02 a
Red oak 0-01 a 0-01 a 0.13 a 0-08 a 0-05 a 0.01 a
Silver maple 0-05b 1.20b 4.10b 0.24b 0.12b 0.04b
Hybrid poplar 0-03 b 0.01 a 3-56 b 0.29 b 0.11 b 0-05 b
White ash 0.01 a 0.02 a 0.24 a 0.08 a 0-04 a 0.01 a
Net stemflow (kg-ha-') = Stemflow (kg-ha") - Rainfall (kg-ha-'). Values followed by the same letter by colurnn are not significantly different at ps 0.05.
on how rapidly litter leaches and decornposes For efficient and economic use of
fertilizers in intercropping systems, it is essential to understand the cycling of
nutrients in intercropping systems. The cycling of nutrients must be considered
when wheat or other crops and tirnber are removed from the intercropping system,
because it will influence prirnary productivity in the ecosystem.
A ) Annual nutrient inputs
Annual nutrient inputs (kg-ha-') by litterfall, throughfall and stemflow are
shown in Table 3.8. Litterfall, on average, represented 90.5% al1 nitrogen inputs
from the tree vegetation while throughfall and stemflow accounted for 8.9% and
0.6%. respectively. Throughfall, on average. represented 62.7% al1 potassium
inputs while litterfall and stemflow accounted for 35.6% and 1.7%. respectively.
Stemflow. on average. represented 50.3% al1 phosphorus inputs while litterfall and
throug hfall accounted for 37.0% and 1 2.7%,respectively. Litterfall from the
plantation canopy was the major contributor of N, wher-as for some species (e-g.
hybrid poplar, silver maple) throughfall contributed the most K. Stemflow accounted
a very small proportion of the nutrients received at the soi1 surface, but in certain
species (e-g. silver maple, hybrid poplar) contributed the most P. K inputs from net
throughfall comprised 83.7% of the total nutrient input for black walnut, followed by
72.8% for hybrid poplar to 39.9% for red oak. P inputs from net stemfiow comprised
78.6% of the total nutrient input for silver maple, followed by 71 -2% for hybrid
poplar to 20.5% for red oak.
Table 3.8. Annual nutnent inputs ( kg-ha-') by Iitterfall, net throughfall and net sternflow, and associated percentages-
Total-N NO,-N NH,-N P K Ca Mg Black walnut Litterfall 1-74 0-15 0-50 3 -08 3-21 Net throughfall 0-06 0-09 O. 175 2-99 2.21 0-92 Net sternflow 0-01 0.004 0.32 0-08 0.06 0-02 Total 1 -74 0-07 0-1 O 0.63 3-57 5-35 4.16
LitterfaIl 23.7% 14-0% 57.6% 77.3% Net throughfall 3,6% 53% 26.0% 83,7% 41.3% 222% Net stemfiow 0,37% O-21% 50.3% 2.30% 1-10% OSO?! Red oak Litterfa t l 4.6 0.35 1-87 1 1-09 3-29 Net throughfall 0.24 0.34 0-14 1-37 1-39 0-42 Net stemflow 0-01 0-01 0-13 0 -08 0-05 0-01 Total 4.6 0.25 0-35 0-62 3-25 12.53 3-73
Litterfa Il 56.8% 57.6% 885% 88.3% Net throughfall 5.1% 7.3% 22.7% 39.9% 11-1% 11.3% Net stemflow 0.17% - 0.26% 20.50% 0.25% O-40% 0-40% Silver maple LitterfaIl 15.22 0.99 3.13 15.51 2.50 Net throughfall 2-73 3.05 0-1 2 7.67 8.93 2-77 Net stemflow 0.05 1 -20 4.10 0-24 0.12 0.04 Total 15-22 2.78 4.25 5.21 1 1.04 24.56 5-31
LitterfaIl 19.0% 28.4% 63.2% 47.1% Net throughfall 17-9% 2OcO3/o 2.4% 69.5% 36.4% 522% Net stemflow 0.31% 7.9% 78.6% 2-1% 0,4% 0,7% Hybrid poplar litterfall 10.99 1 .O6 5.49 28.51 7.27 Net throughfall 1.75 0.73 0.38 15.44 8-99 2-77 Net stemf ow 0.03 0.07 3.56 0-29 0.1 1 0.05 Total 10.99 1.78 0-74 4.99 21 -22 37.61 10-03
LitterfaII 21.2% 2Sc9% 75.8% 725% Net throughfall 15.9% 6.6% 7.5% 72.8% 23.9% 27.1%
0.29% O-07% 71.2% 1,3% 0.30% 0.47% Net stemflow White ash LitterfaIl 4-88 0.51 1 -84 13.38 2.37 Net throughfall 0.32 0.10 0.048 1-63 2-02 0.62 Net stemfiow 0.01 0.002 0.24 0.08 0-04 0.01 Total 4.88 0.33 0-1 1 0.79 3-55 1 5.44 3-01
LitterfaIl 64.5% 51.8% 86_66% 7874Dh Net throughfall 6-6% 2.2% 4.8% 459% 1 3-1% 20206?! Net sternfiow 0.15% 0.03% 30.7% 2.3% 0.28% O.Wh
2) Soil nitrogen
Cornparisons of nitrogen concentrations (% dry weight. pg-100g-'SD) in the
0-20cm soi1 layer at different distances frorn tree rows under different tree species
at the intercropping system are shown in Table 3.9. Total N concentrations (% dry
weight), at distances of 1,0m, 3-5m and 6.0m from the tree row, were not
significantly different under any tree species, whereas total N concentrations within
tree species at a distances of 1 -Orn and 3.5m from tree row were significantly
different. There was no significant difference in soi1 NO,-N or NH,-N within species
across the three distances. NO,-N concentrations in the soi1 (pg-100g") at the
distances of 1.0m from tree row were significantly different from those at a distance
of 6.0m for black walnut, red oak, silver maple and hybrid poplar but not white ash.
There was no significant difference of NH4-N concentrations within 1.0m, 3.5m and
6.0m from tree row for the most tree species although the NH,-N concentrations of
hybrid poplar at the distance of 1.0m from tree row was different from that at a
distance of 6.0m.
Seasonal sampling (June, July, August) of soi1 NO,-N and NH4-N indicated
that the highest soi1 NOzN concentrations were found in July. The highest soi1 NH,
N concentrations were found at the beginning of the sarnpling season in June.
Estimated quantities of soi1 nitrogen content (kg-ha-') in the 0-20 cm soi1
layer at different distances from tree rows under different tree species at the
intercropping system are shown in Table 3.1 0. Soil total N ranged from 41 06 kgeha-'
for silver maple at a distance of 3.5m from tree row to 3043 kg-ha" for red oak at a
53
Table 3.9. Cornparison of nitrogen concentrations in the 0-20 cm soi1 layer at different distances from tree rows under different tree species at the intercropping system.
Soil nitrogen concentrations by different distances from tree row Species 1,Om 3.5m 6,Om
TN NO3-N NH4-N TN NO3-N NH4-N TN NO34 NHA-N (W (pg'100") (%) (~g*loO'l) (%) (C(g*IOO")
Black walnut 0,14 a 1392.53 a 232,49 a 0,14 a 856,16 a 122,81 a 0,14 a 532,43 a 209,33 a ~1 f0,002(a) &604,75(a) k l 71 .85(a) 10.02(a) &718,86(a) 1137.88(a) 10.02(a) 1514,81 (b) 1323,48(a) A
Red oak 0,13 ab 1235,47 a 333,19 a 0,13 a 998,47 a 155,81 a 0.13 a 552,47 a 162.21 a 10.01 (a) 1547.49(a) *358,58(a) 10.09(a) 1662.90(a) 11 gO.ig(a) 10.01 (a) t311,77(b) 11 48,94(a)
Sîlver maple 0,16 a 1203.46 a 287,55 a 0.17 b 722,06 a 299.95 a 0,14 a 433,Ol a 224,66 a 10.02 (a) 161 8.25(a) 11 74,66(a) tO.O1 (a) 1387,33(a) 1256.66(a) 10,05(a) t215,94(b) f 172.61 (a)
Hybrid poplar 0.16 a 97661 a 331,59 a 0,17 b 523.59 a 194,83 a 0,16 a 370,89 a 145,51 a 10.02 (a) k608.94(a) +l56,83(a) tO.O1 (a) 1444.51 (a) 11 3l,54(a) +0.01 (a) 11 57.99(b) 1145,32(b)
White ash 0,17 ac 1016.69 a 238,48 a 0.168 b 61564 a 183.10 a 0.16 a 509,02 a 306,52 a 10.01 (a) î655.27(a) +lOl.65(a) 10,02(a) f503.82(a) f l36,24(a) 10,02(a) 1337,12(a) 11 78,24(a)
- - - -- -- -
Values followed by the same letter or letter pairs by column across species, or by (row) across distance for the same nutrient element are not significantly different at ps; 0,05,
Table 3.1 0. Estimated quantities of soi1 nitrogen content (kg-ha-') in the 0-20 cm soi1 layer at different distances from tree rows under different tree species in the intercropping system.
Nitrogen content by different distances from tree row Species 1.0m 3.5m 6,Om
TN NO3-N NH4-N TN NO3-N NHA-N TN NOrN NHcN (kg~ha'')
Black watnut 3432.0 a 33.4 a 5.6 a 3271.2 a 20.6 a 2.9 a 3250,O a 12.8 a 5.0 a
Red oak 3225.6 ab 29.7 a 8,O a 3163.2 a 24.0 a 3.7 a 3043,2 a 13.3 a 9,9 a (a) (a) (a) (a) (a) (a) (a) (b) (a)
Silver maple 3921.6 a 28.9 a 6.9 a 4106.4 b 17.3 a 7.2 a 3408.0 a 10.4 a 5.4 a (a) (a) (a) (a) (a) (a) (a) (b) (a)
Hybrid poplar 3876.0 a 23.4 a 8.0 a 4070.4 b 12.6 a 4.7 a 3868.8 a 8.9 a 3.5 a (a) (a) (a) (a) (a) (a) (a) (b) (b)
Values followed by the saine letter or letter pairs by column across species, or by (row) across distance for the same nutrient element are not significantly different at ps 0.05.
distance of 6.0rn. Soif NH,-N ranged frorn 9.89 kg-ha-' for red oak at a distance of
6.0m to 2.95 kg-ha-' for black walnut at a distance of 3.5m. Soi1 NO,-N within 1 -0rn
of the tree row for black walnut were 2-62 times the content at a distance of 6.0m;
for red oak, 2.24 times; for silver maple, 2.78 times; for hybrid poplar, 2.63 times.
3.4.2 Wheat growth response
1) Wheat tillers
The average annual number of wheat tillers per plant (tillers-plant-') by
different distances frorn tree rows under different tree species at the intercropping
system are shown in Table 3.1 1. The number of wheat tillers per plant by distances
of 1.0m. 3.5m and 6.0m from the tree rows. across the five species ranged frorn 5.8
tillers*plant-' for white ash at a distance of 1.0m from tree row in 1997 to 2.0
tillers-plant-' for black walnut at a distance of 6.Om in 1998. Wheat tillers per plant
within 1.0m of the tree row for black walnut were 1.57 and 1.75 times (in 1997 and
1998 respectively) those at a distance of 6.0m; for red oak, 1.33 in 1997 only; for
silver maple. 1.33 times (1998 only); for hybrid poplar, not significant and for white
ash. 1.66 and 1.42 times. The average nurnber of wheat tillers per plant at any
distance in both 1997 and 1998 were not affected by the presence of any particular
tree species-no sig nificant differences existed.
2) Wheat biomass
The average accumulated wheat biomass (kg-ha-') by different distances
56
Table 3.1 1. Wheat growth response (tillers-plant-') at different distances from tree rows under different tree species in the intercropping system-
(tillers-plant-'Hl) by distances from tree rows S pecies 1997 1998
1 -0m 3-5m 6 -0m 1 -0rn 3-5m 6-Om Black walnut 4.7 a 3-5 a 3-0 ab 3-5 a 2-8 a 2-0 a
10.2(a) 10.3(b) &0.7(bc) i0.7(a) *O-4(ab) 10.5(b)
Red oak 4-4 a 3-8 a 3-3 a 2-9 a 2-2 a 2-3 a îO_4(a) *O-3(a) &0.3(bc) *0,5(a) I0S(a) *0.7(a)
Silver maple - - - 3.2 a 2.6 a 2-4 a *0_3(a) *O .2(b) IO. 1 (b)
Hybrid poplar 4.5 a 4.2 a 3.9 ac 3.5 a 2.6 a 2.5 a *0.5(a) *O -7(a) &O 3(a) 11 4(a) Ii0-6(a) *0.4(a)
White ash 5-8 a 3.6 a 3 - 5 a 3-7 a 3.3 a 2-6 a 11.3(a) 10-5(b) *0.6(bc) *0.6(a) &0.7(ab) i0.4(b)
Values followed by the same letters or letter pairs by ( row) across distance or by column across species are not significantly different at ps 0.05.
from the tree rows under different tree species are shown in Table 3.12. The mean
of 1997 and 1998 of annual wheat biomass (kg-ha-') by distances of 1 .Omr 3.5m.
6.0m from tree rows, across the tree species ranged from 9833 kg-ha-' for white ash
at a distance of 1 .Om to 5038 kg-ha-' for black walnut at the distance of 6.0m from
tree row. Significant differences were found across distances in both 1997 and
1998. For the species comparÏson, significant differences in wheat biomass existed
only between red oak and white ash at a distance of 1 .Om in 1997. The average
annual wheat biornass under black walnut within 1 .Om of the tree row was 1.69 and
2.01 times, for 1997 and 1998 respectively the annual wheat biomass at a distance
of 6.Om; for red oak, 1.36 and 1.82 times; for silver maple. 2.23 times (1998 only);
for hybrid poplar. 1.45 times (1 998 only); and for white ash, 1.49 and 1.49 times-
The two year mean, with al1 distances combined, ranged from 7748 kg-ha-' for white
ash to 6545 kgoha-' for red oak.
3) Wheat yields
The average annual wheat yields (kg-ha-') by different distances from tree
rows under different tree species at the intercropping system are shown in Table
3.1 3. The wheat yields were significantly different between the distance of 1.0 m
and 6.0m from the tree rows. Wheat yield ranged from 5046 kg-ha'' for white ash
at a distance of 1.0m from tree row in 1997 to 1800 kgha-' for black walnut at a
distance of 3.5m in 1998. Wheat yields within 1.0m of the tree row for black walnut
were 1.71 and 2.32 (in 1997 and 1998 respectively) those at a distance of 6.Om; for
Table 3.12. Wheat biomass (kg-ha-') at different distances from tree rows under different tree species in the intercropping system-
Annual wheat biornass (kg-ha-'SD) by distances from tree rows Species 1997 1998
1-Om 3.5m 6.0m 1 ,Om 3-5m 6-0m Mean Blackwalnut 9400 a 7300 a 5550 a 9100 a 4330 a 4525 a 6701
e21(a) 1154(ab) 1161(b) 181 (a) i 4 1 (b) 163(b)
Red oak 7400ab 7450a 5450a 8980a 5055a 4935a 6545 *15l(a) i45(a) ~ l O l ( b ) i76(a) i 81 (b ) 1114(b)
Siiver maple - - - 9545 a 5795 a 4710 a 6683 11 33(a) 11 O8(b) 11 26(b)
Hybrid poplar 8450 a 8100 a 7200 a 8580 a 5360 a 5915 a 7268 *154(a) i209(a) 133(a) &%(ab *93(b) 130(b)
White ash 17700ac 7750a 7850a 7965a 5880a 5340a 7748 i215 (a) t149(b) I 2 8 (b) 11 75(a) i62 (ab) 11 O8(b)
Values followed by the same letters or letter pairs by (iow) across distance within years or by column across species are not significantly different at ps0.05.
red oak, 1.45 and 1.97 times; for silver maple, 1.90 tïmes (1 998 only); for hybrid
poplar. 1.49 times (1 998 only) and for white ash, 1.54 and 1.52 times. Wheat yiekls
at any distance in 1998 were not significantly different between tree species. In
1 997, some minor differences in wheat yield were noticed between the white ash
and other treatments but only at tom; no differences were noticed at other
distances. The two year mean, with al1 distances combined, ranged from 3394
kg-ha-' for white ash to 2858 kg-ha-' for red oak.
The winter wheat grain yields in the intercropping system and in an
monocropping system were estimated using data from this study. Assuming that the
distance between tree rows is 15m and that the yield of the centre plot (a distance
of 6.0m - 9.0m from one side of tree row) is equivalent to the yield found in a
monocropping system, the yields in the intercropping and monocropping situations
were 2450.3 kg-ha" and 2244.4 kgoha-' respectively. There was a 8.4% yield
increase in the intercropping system compared to the monocropping system-
Excluding land occupied by the tree rows, these yields are equivalent to those found
on adjacent monocropped fields-
4) Wheat grain total nitrogen
Average concentrations of wheat grain total N (% dry weight) by different
distances from tree rows under different tree species at the intercropping system
are shown in Table 3.14. There was no significant difference among the wheat grain
TN concentrations within the five studied tree species, across the three distances
Table 3.1 3. Wheat yield (kg-ha-') at different distances from tree rows under different tree species in the intercropping system.
Annual wheat yield (kgoha-'k SD) by distances from tree rows
S pecies
Black walnut 41 36 ab 2991 a 2421 a 4351 a 1800 a 1877 a 2929 1127(a) 152 (ab) 157 (b) d24 (a) i27 (b) G!9 (b)
Red oak 3309a 3237a 2287a 4053a 2200a 2062a 2858 fil (a) I 2 7 (a) 149 (b) *29 (a) 145 (b) 152 (b)
Silver maple - - - 4516 a 2722 a 2375 a 3204 179 (a) 160 (b) k61 (b)
Hybrid poplar 3086 a 3357 a 2923 a 3726 a 2128 a 2495 a 2953 172 (a) 6 7 (a) 115 (a) 141 (a) 164 (b) k12 (b)
White ash 5046b 3339a 3282a 3643a 2643a 2413a 3394 188 (a) 164 (b) il 18(b) 166 (a) 134 (b) 151 (b)
Values followed by the same letters or letter pairs by ( row) across distance within years or column across species are not significantly different at ps0.05.
Table 3.14. Average total nitrogen concentrations of wheat grain (% dry weight) at different distances from tree rows under different tree species in the intercropping system-
Wheat grain TN (% dry weig ht f SD) by distances from tree rows Species 1 -0m 3-5m 6.0m Black walnut 1-91k0-28 a (a) 1,7810.12 a (a) 1.9110-21 a (a)
Red oak 1 -68k0.15 a (a) 1-71f0.11 a (a) 1 -8810.05 a (b)
Silver maple 1 -94k0.25 a (a) 1.81k0-18 a (a) 1.941021 a (a)
Hybrid poplar 1 -68I0.08 a (a) 1-77k0.11 a (a) 1-75I0.13 a (a)
White ash 1 -76*0-20 a (a) 1 -7910-1 4 a (a) 1 -89*0- 1 0 a (a)
Values followed by the same letten by column across species. or by (row) across distance are not significantly different at ps 0.05,
of 1.0m. 3.5m and 6.0m. Signifiant difference among grain TN concentrations were
only found in the red oak treatment. where wheat grain TN at 6.0m from the tree
row was significantly higher than at either 1.0m and 3.5m.
Estimated quantities of wheat grain total N content (kg-ha-') by different
distances from tree rows under different tree species at the intercropping system
are shown in Table 3.15. Annual wheat grain total N
distances of 1 .Om, 3.5m and 6-0m from the tree rows,
content (kg-ha-'-yr') by
across the five species
ranged from 87.79 kg-ha" for silver maple at a distance of 1 -0m from tree row to
31 -80 kg-ha-' for black walnut at a distance of 3.5~1. Wheat grain total N content
within I.Om of the tree row for black walnut were 2-34 times the content at a
distance of 6.0m; for red oak, 1.75 times; for silver maple, 1.93 times; for hybrid
poplar, 1.43 times and for white ash. 1 -42 times. An average 51 -99 kg TN per
hectare was removed annually from wheat grain harvest at the studied field with the
five tree species.
The above results indicate that the trees in the studied intercropping system
provided additional nutrients to adjacent crops. Winter wheat, which is planted in
the previous fall and grows mostly in the spring before the tree leaves flush out,
benefts from tree nutrient inputs. Wheat apparently does not compete with trees for
Sun light and fully uses the fertilizer inputs from the trees.
5) Implications and recommendations
63
Table 3.1 5. Estimated total nitrogen contents of wheat grain (kg-ha") at different distances from tree rows under different tree species in the intercropping systern in 1998-
Wheat grain TN content (kg-ha-') by distances from trees
Species 1 -0m 35m 6-0m
Black walnut 83-56 a (a) 31 -80 ab (b) 35.78 a (b)
Red oak 67.86 a (a) 38-04 a (b) 38-72 a (b)
Silver maple 87-79 a (a) 49-22 ac (b) 45-41 a (b)
Hybrid poplar 62-75 a (a) 37.26 a (b) 43.80 a (b)
White ash 65.02 a (a) 47.21 a (a) 45-70 a (a) Values followed by the sarne letten or letter pairs by ( row) across distance or by column across species are not significantly different at p i 0.05.
Greater amounts of cations, especially potassium, were found in throug hfall
compared to litterfall and stemflow presurnably because the cations in foliage were
available for leaching. However. nitrogen and phosphorus were less available for
leaching due to translocation from the foliage and because they primarily present
in organically-bound forms.
While the nutrient fiuxes of Iitterfall, net throughfall and net sternflow varied
among tree species, no correlation were found between these parameters and
wheat yield and biomass and soi1 nitrogen content. This is rnost likely because of
difierences in decomposition rates of foliage and accumulation processes. The
foliage of silver maple and hybrid poplar decomposes faster than red oak, black
walnut or white ash. Leaves of red oak, for example. contain more lignin which
takes a longer time to breakdown. The compound ieaves of black walnut and white
ash are arched which allow individual leaflets to rest off the ground, making them
harder to decay. In addition, the trees at the study site are 13 years old and It is
difficult to interpret the history of nutrient accumulation that has occured over the
period of the study. More research is necessary to further explain the results.
The total nitrogen content of wheat grain ai l m from the tree rows was 20 to
49 kg-ha-' more than that of wheat grain at a distance of 6m. The additional nitrogen
came not only from the nutrient inputs of litterfall. throughfall and stemflow but also
from decomposing fine tree roots.
The results indicate that farmers could consider growing wheat next to tree
rows. Farmers may either fertilize more in the middle of the alley between the tree
65
rows to increase the yield in that area or reduce fertilization close to the tree rows
to lower costs-
4- CONCLUSIONS
The annual nutrient inputs from tree vegetation are a significant contributor
to nutrient availabilit. in a intercropping system.
The average annual nutrient inputs by litteifall for N, P, K. Ca and Mg were
7.49, 0.61, 2.57, 14.31 and 3.24 kg-ha-'-yrt. respectively (Ca > N > Mg > K > P).
The average annual nutrient input by net throughfall for NO,-N, NH,-NI P. K. Ca and
Mg were 1.02, 0.86. 0.17. 5.81. 4.71 and 1.49 kg-ha4-yfl, respectively (K >Ca >
NO3-N+NO,-N > Mg >P). The average annual nutrient inputs by net stemflow for
NO3-N, NH,-NI P. K. Ca and Mg were 0.014, 0.25, 1.62, 0.15. 0.08, and 0.03
kg-ha-'-yr', respectively (P > NO3-N+NO,-N >K > Ca > Mg). Litterfall, on average.
represented 90.5% al1 nitrogen inputs from the tree vegetation while throughfall and
stemflow accounted for 8-9% and 0.6%, respectively. Throughfall, on average,
represented 62.7% al1 potassium inputs while litterfall and stemflow accounted for
35.6% and 1.7%. respectively. Stemflow, on average. represented 50.3% al1
p hosp horus inputs while litterfall and throughfall accounted for 37.0% and
12.7%,respectively. Litterfall from the plantation canopy was the major contributor
of NI whereas throughfall contributed the most K and stemflow accounted for a very
small proportion of the nutrients but contributed the most P.
The average annual total-N input by litterfall for silver maple, hybrid poplar.
white ash, red oak and black walnut were 15-22. 1 0.99.4.88.4.62 and 1.74 kg-ha-'.
respectively. The average annual P inputs by Iitterfall. net throughfall and net
stemfiow for silver maple, hybrid poplar, white ash, black walnut and red oak were
5.21.4.99 0.79. 0.63 and 0.62 kg-ha-'. respectively. The average annual K inputs
by litterfall, net throughfall and net stemflow for hybrid poplar, silver maple. black
walnut, white ash and red oak were 21 -22. 11 -04. 3.57. 3.55 and 3.25 kg-ha-'.
respectively .
Inputs of N from tree vegetation result in increased soil inorganic N during the
growing season. The average soi1 inorganic N content within 1.0m of the tree row
was 2.1 0 times the soi1 inorganic N content at a distance of 6.0rn. The average
annual wheat grain total N content at 1 -0rn of the tree row was 1 -75 tirnes the grain
total N content at a distance of 6.0m, and the average annual wheat yield at 1.0m
of the tree row was 1.60 times the wheat yield a i a distance of 6.0m.
The study demonstrates that wheat grown adjacent to tree rows benefits from
the additional nutrients contributed by litterfall, throughfall and stemflow. Among the
five tree species in the studied intercropping system, silver maple and hybrid poplar
were the best species in terms of nutrient input.
Abee, A., and D.P. Lavender. 1972. Nutrient cycling in throughfall and Iitterfalll in a 450-year-old Douglas-fir stand. pp.133-143. In J.F. Franklin et al. (eds.) Proceedings, Research on Coniferous forest Ecosystems. USDA For. Serv. PNW For. Range Exp. Sta., Portland, Ore.
Allen, H.L. and A.R. Gillespie. 1991. Leaf area variation in midrotation loblolly pine plantations. Forest Nutrition Cooperative, College of Forest Resources, North Carolina State University, Releigh. NCSFNC Res. Note 6-
Amezaga, I., A. Gonzalezarias, M. Domingo, A. Echeandia and M. Onaindia. 1996. Atmospheric deposition and canopy interactions for conifer and deciduous forests in northern Spain. Water, Air, and Soil Pollution 97: 303-31 3-
Arthur, M.A. and T.J. Fahey. 1992. Throughfall chemistry in an Engelmann spruce-subalpine fir forest in north central Colorado. Can. J. For. Res. 231738-742-
Ashton, D.H. 1975. Studies of litter in Eucalyptus regnans forests. Aust. J. Bot- 23141 3- 433.
Attiwill, P.M. 1966. The chernical composition of rainwater in relation to cycling of nutrients in mature Eucalyptus forest. Plant and Soil 24:390-406.
Attiwill, P.M., H.B. Guthrie and R. Leunig.1978. Nutrients cycling in a Eucalyptus obliqua (C Herït.) Forest. 1. Litter production and nutrient return, Aust. J- Bot. 26:79-91,
Baker, T.G. 1983. Dry matter, nitrogen, and phosphorus content of litter-fall and branch-fall in Pinus radiata and Eucalyptus forest. N-Z- J . For. Sci. 1 31205-221 -
Ball, D.H. 1991. Agroforestry in southern Ontario: a potential diversification strategy for tobacco farmers. M.Sc. Thesis, University of Guelph, Guefph, Ontario.
Bergman, W. 1993. Nutritional disorders of plants development. Visual and analytical diagnosis. Gustav Fisher Verley Jena. Stuttgart, New York.
741 pp.
Bevege, D.I. 1978. Biomass and nutrient distribution in indigenous forest ecosystems. Technical Paper No. 6 Department of Forestry, Queensland (Australia).
Binkley, D. 1982. Nitrogen fixation and net prÏrnary production in a young Sitka alder stand. Can, J. Bot- 60:281-284.
Birk, E. and P.M. Vitousek. 1986. Nitrogen availability and nutrient use eficiency in loblolly pine stands. Ecology 67:69-79.
Blew, R.D., D.R. lredale and D. Parkinson. 1993. Throughfall nitrogen in a white spruce forest in southwest Alberta, Canada. Can. J. For. Res. 2312389-2394,
Bowen, H.J.M. 1979. Environmental Chemistry of the elements. Acadernic Press, London, pp. 333.
Bowen, G.D. and E.K.S. Nambiar (eds,). 1984. Nutrition of plantation forests- Academic Press, London. pp147-179.
Brand, D.G. 1987. Estimating the surface area of spruce and pine foliage from displaced volume and length. Can. J. For. Res. 17:1305-1308.
Brasell, H-M- and Sinclair, D.F. 1983. Elements returned to forest floor in two rainforest and three plantation plots in tropical Australia, J. Ecol. 71 :367-378.
Bray, J.R. and E. Gorham. 1964. Litter production in forests of the world. Adv. Ecol. Res. 2:101-157.
Breckle, S.W. and H. Kahle. 1992. Effects of toxic heavy metals (Cd, Pb) on growth and mineral nutrition of beech (Fagus sylvatica L.). Vegetation 101 :43-53.
Brown, J,., J.R., and AC. Barker. 1970. An analysis of throughfall and stemflow in mixed oak stands- Water Resour-Res. 6:316-323-
Buresh, R.J. and G. Tian. 1998. Soi1 improvernent by tree in sub-Saharan Africa. Agroforestry Systems 38:51-76.
Butler, T.J. and GE. Likens. 1995. A direct cornparison of throughfall plus stemflow to estimate of dry and total deposition for sulfur and nitrogen. Atmos. Environ, 293 253-1 265.
Byington, E.K. 1990. Agroforestry in the temperate zone. In K.G. MacDicken and N .T.Vergara, Agroforestry Classification & Management A Wiley- interscience publication JOHN WILEY & SONS. pp. 228-
Cartisle, A., A.H.F. Brown and E.J. White. 1965. The interception of precipitation of oak (Quercus petraea) on a high rainfall site. Q. J. For. 59 11 40-1 43.
Carlisle, A., A.H.F. Brown, and E.J, White- 1967. The nutrient content of tree stemflow and ground fiora litter and leachates in a sessile oak (Quercus petraea) woodland. J. Ecol. 55:615-627.
Carlisle, A,, A. Brown and E.J. Mite . 1967. The nutrient content of rainfall and its role in the forest nutrient cycle. Proc.14th Congr. Int. Union For. Res. Org. Munich, Part II, Sect. 21, pp. 145-158.
Carlisle, A., A.H.F. Brown and E.J. White. 1966. The organic matter and nuhient elements in precipitation beneath a sessile oak canopy. J. Ecol. 54:87-98.
Carlisle, A,, A.H.F. Brown, and E.J. White, 1966. Litterfall, leaf production and the effects of defoliation by Torfix vrndiana in a sessile oak (Quercus petraea) woodland. J. Ecol. 54:65-85.
Chourrnouzis, C. 1995. The partitioning of rain water in 27 year old, plantation grown, red, white and black spruce. M. Sc. Thesis, Univ. Guelph Canada, 121pp.
Cole, D.W., M. Rapp. 1 981 . Elemental cycling in forest ecosystems. In Dynamic properties of forest ecosystems. Edited by DE. Reichle-Cambridge University Press, Cambrige, pp.34l-410.
Cole, D.W., S.P. Gessel and S.F. Dice. 1967. Distribution and cycling of nitrogen, phosphorus, potassium and calcium in a second-growth Douglas-fir ecosystem. In Symposium on primary productivity and mineral cycling in natural ecosystems. Am. Assoc. Adv. Sci. pp.197-233.
Correll, D.L. 1983. N and P in soils and runoff of three coastal plain land use. In:Lowrance, R. et al. (eds.) Nutrient Cycling in Agricultural Eco-systems. University of Georgia Special publication No.23. Athens, Georgia.
Crockford, R.H. and D-P- Richardson. 1998. Litterfall, litter and associated chemistry in a dry sclerophyll eucalypt forest and a pine plantation in
south-eastern Australia: 2. Nutrient recycling by Iitter, throughfall and stemflow, Hydrol. Processes 12:385-400.
Crockford, R.H. and P.K. Khama. 1997. Chemistry of throughfall, stemflow and Iitterfall in fertilized and irrigated pinus radiafa. Hydrological Processes 1 1 :l493-150?-
Daniels, R B . and J.W. Gilliarn. 1996, Sediment and chernical load reduction by grass and riparian filters. Soil Science Society of America Journal 60 1246-25 1,
Duvigneaud, Pl and Denaeyer-DeSmet, S. 1 970. Biological cycling of rninerals in temperate decid uous forests, In Analysis of Temperate Forest Ecosystems, Edited by D.E. Reichle. Springer-Verlag. New York, pp. 199- 225.
Eaton, J.S., G.E. Likens and F.H. Bormann. 1973. Throughfall and stemflow chemistry in a northern hardwood forest. J. Ecol. 61:495-508.
Fenn. M.E. and A. Bytnerowicz. 1997. Surnmer throughfall and winter deposition in the San bernardin0 mountains in southern California. Atmospheric Environment 3 1 :673-683.
Field, C. 1991. Ecological scaling of carbon gain to stress and resource availability, In response of plants to multiple stresses. Edited by HA. Mooney, W.E. Winner, and E.J. Pell. Academic Press. San Diego, Calif. pp.35-65.
Field, C., and H.A. Mooney. 1986. The photosynthesis-nitrogen relationship in wild plants. In on the economy of plant form and function. Edited by T.J. Givinish. Cambridge University Press. New York. pp. 25-55.
Foster, N.W., and S.P. Gessel. 1972- The natural addition of nitrogen, potassium and calcium to a Pinus banksiana Lamb. forest floor. Can. J . For. Res. 2:448-455.
Foster, N.W. 1974. Annual macroelement transfer from Pinus banksiana Lamb. forest to soil. Cam 3. For. Res. 4:470476-
Foyer, C. And C. Spencer.1986. The relationship between phosphate status and photosynthesis in leaves. Planta. 1 67:369-375.
Garrett, H.E., J.E. Jones, W.B. Kurtz, and J.P. Slusher. 1991. Black walnut
(Juglans Nigra L.) Agroforestry - its design and potential as a land-use alternative. Forestry Chronicle 67:213-218.
Gavlak, R.G., D.A_ Horneck, and R.O. Miller. 1997. Western states laboratory proficiency testing program soi1 and plant analytical methods (Version 4.00). P.114-116. Fromr Plant. Soil and Water Reference Methods for the Western Region. WREP 125.
Gersper, P.L., and N. Holowaychuck. 1970. Effects of stemflow water on a Miami soi1 under a beech tree. 1. Morphological and physical properties. II. Chemical properties. Soil Sci. Soc. Amer. Proc. 34:779-786, 786-794.
Gold, M.A. 1995. Opportunities for agroforestry in the 1995 farm bill. Association for temperate agroforestry (AFTA).
Golley, F.B. 1983. Nutrient cycling and nutrient conservation. In tropical rain forest ecosystems. Edited by F.B. Golley. Elsevier, Amsterdam. pp.137-156.
Gordon, A.M. and N.K. Kaushik. 1987. Riparian forest plantations in agriculture: the beginnings. Highlights of Agrïcultural Research in Ontario 1016-8.
Gordon, A.M. and S.M. Newman. 1997, CAB INTERNATIONAL, Temperate Agroforestry Systems.
Gordon, A.M. and P.A. Williams. l99 l . lntercropping valuable hardwood tree species and agricultural crop in southern Ontario. Forestry Chronicle 671200-208.
Gosz, J.R., GE. Likens, and F.H. Bormann. 1972. Nutrient content of litter faIl on the Hubbard Brook experimental forest, New Hampshire. Ecol. 53:769- 784,
Grewal, S.S., M.L. Juneja, K. Singh and S. Singh. 1994. A cornparison of two agroforestry systems for soil, water and nutrient conservation on degraded land. Soil Technology 7:145-153.
Grier. C C , K.A. Vogt., M.R. Keyes and R.L. Edmonds. 1981. Biomass distribution and above-and below-ground production in young and mature Abies amabilis zone ecosystems of the Washington Cascades. Can. J. For. Res. 1 1 355-167.
Gutschick, V.P. and F.W. Wiegel. 1988. Optimizing the canopy photosynthetic
rate by patterns of investment in specific leaf mass. Am. Nat. 132:67- 86.
Hanawalt, R.B. 1969a. Environmental factors influencing the sorption of atmospheric ammonia by soils. Soil Sci. Soc. Am. Proc. 33:231-238.
Hanawalt, R.B. 1969b. Soil properties affecting the sorption of atmospheric ammonia. Soil ScL Soc- Am. Proc, 335'25-729-
Hart, G E and D R Parent. 1973. Chemistry of throughfall under Douglas fir and rocky mountain juniper. The American Midland Naturalist pp.191- 201,
Hegyi, F. 1972. Dry matter distribution in jack pine stands in northern Ontario. For. Chron, 48:l-5.
Helmissiari, H.S. 1990. Temporal variation in nutrient concentrations of Pinus sylvestris needles. Scandinavian Journal of Forest Research. 5377-1 93.
Helvey. J.D. and J-H-Patric. 1965. Canopy and Iitter interception of rainfall by hardwoods of eastern United States. Wat. Resour- Res. 1 :193-206-
Henderson, G.S., W.F. Harris, D.E. Todd, Jr, and T. Grizard. 1977, Quantity and chemistry of throughfall as influenced by forest-type and season. J . Eco~. 651365374,
Hovmand, M.F. and H.V. Angersen. 1995. Nine years of measurements of atmospheric nitrogen and sulfur deposition to Danish forest. Wat. Air soi1 Potlut- 85:2205-22lO.
Ingestad, T. and G.I. Agren. 1991. The influence of plant nutrition on biomass allocation. Ecol. Appl. 1 :168-174.
Innes, J.L. 1993. Foliar analyses. In Forest health: it assessrnent and status (Edited by John L. Innes). Chap. 9. Wallingford, UK.
Jordan, C.F. 1982. The nutrient balance of an Amazonian rain forest. Ecology 631647-654,
Jordan, CF.. F. Golley, J-D. Hall and J. Hall. 1979. Nutrient scavenging of rainfall by the canopy of an Amazonian rain forest. Biotropica 12:61-66.
Keeney, D.R. and D.W. Nelson. 1982. Nitrogen - inorganic forms. p. 643-696
in Page, A And D. Keeney (eds.). Methods of soif analysis, part 2:chemical and microbiolog ical properties. 2nd ed. American Society of Agronomy, Soil Science Society of America. Madison, Wisconsin.
Kellrnan, M.. and A. Carty. 1986. Magnitude of nutrient in fluxes from atmospheric sources to a central American Pinus caribeae woodland. J. Appl. Eco~. 23121 1-226.
Kirnmins, J.P. 1987. Water: The material that makes Iife possible. In: Forest ECO~O~Y. ch.11 pp. 268-270.
Kimmins, J.P. 1997. Forest ecology (Second edition). pp. 90-93. 241. 274.
King, K.F.S. 1979. Concepts of agroforestry. in T. Chandler and D. Spurgeon (eds.). Proceedings of an International conference on International Cooperation in Agroforestry. Nairobi, Kenya. July 16-21. 1979. lnternational Council for Research in Agroforestry, Nairobi, Kenya. pp.1-13-
Landford, A.O. and F-C. Fehsenfeld. 1992. Natural vegetation as a source or sink for atmospheric ammonia: a case study. Science 255:58 1-583-
Lee, K.E. and R.L. Correll. 1978. Litter fall and its relationship to nutrient recycling in a south Australian dry sclerophyll forest. Aust. J. Ecol. 3: 243-252.
Leonard, R.E. 1 961. Interception of precipitation by northern hardwoods. US DA For. Serv., NE For. Exp. Sta., Upper Darby. Station Paper No. 159. 16pp.
Li. Y.C.. A.K. Alva, D.V. Calvert and M. Zhang. 1997. Sternflow. throughfall, and canopy interaction of rainfall by citrus tree canopies. Hort. Science 3211 059-1 060.
Li, Y.C., A.K. Alva. D.V. Calvert and M. Zhang. 1997. Chernical composition of throughfall and stemflow from chus canopies. Journal of Plant Nutrition 20:1351-1360-
Lin, TC.. S.P. Hamburg, H.B. King and Y.J. Hsia. 1997. Spatial variability of throughfall in a subtropical rain forest in Taiwan. J. Environ. Qual. 26: 172-1 80.
Lindberg, S.E.. G.M. Lovett, D.D. Richter and D.W. Johnson. 1986. Atmospheric deposition and canopy interactions of major ions in a forest. Science 231 :141-145.
Linder. S. and D.A. Rook. 1984. Effects of mineral nutrition on carbon dioxide exchange and partitioning of carbon in trees. In Nutrition of plantation forests. Edited by G.B.Bowen and E.K.S. Nambiar. Academic Press. London. pp. 21 1-236.
Lovett. G.M., W.A. Reiners and KR. Olson. 1982. Cloud droplet deposition in subalpine baisam fir forests: hydrological and chernical inputs. Science 21 811 303-1 304-
Madgwick. H.A.I. and J.D. Ovingtion. 1959. The chemical composition of precipitation in adjacent forest and open plots. Forestry 32:14-22.
Mahendrappa, M.K. and E.D. Ogden. 1973. Effects of fertilization of black spruce stand on nitrogen contents of stemflow, throughfall, and Iitterfall. Cam J. For. Res. 354-60.
Mahendrappa, M.K. 1974. Chemical composition of stemfiow from some eastem Canadian tree species. Canadian Journal of Forest Research 4: 1 -7.
Malkonen, E. 1974. Annual primary production and nutrient cycle in some scots pine stands. Comm.. Inst. For. Fenn. 84-587 pp.
Malo, B.A.. and E.R. Purvis. 1964. Soil absorption of atmospheric ammonia. Soil Sci. 97:242-247-
Matson, P.A., L. Johnson, C- Billow, J-Miller and R. Pu. 1994. Seasonal patterns and remote spectral estimation of canopy chemistry across the Oregon transect. Ecol. Appl. 4:280-298.
Matsuura. Y., 1. Hotta and M. Araki. 1991. Surface soi1 pH depression of Cryptomeria japonica forests in Kanto district. Japanese Journal of Forest Environment 32:65-69 (in Japanese with English summary).
Matzner, E., and K.J. Meiwes. 1994. Long-term development of element fluxes with bulk precipitation and throughfall in two German forests. J. Environ. Qual- 23:162-166.
McColl. J.G. and D.S. Bush. 1978. Precipitation and throughfall chemistry in the San Francisco Bay area. J. Environ. Qual. 7:352-357.
Mclaughlin, R.A., P.E. Pope and €.A. Hansen. 1985. Nitrogen fertilization and ground cover nitrate leaching. J. Environ. Qual. I4:24lwî45.
Mclean, H.D.J. 1990. The effect of corn row width and orientation on the growth of interplanted hardwood seedlings. MSc. Thesis, University of Guelph. Guelph. Ontario, Canada.
Mina. V.N. 1967. Influence of stemflow on soii, Sov. Soil Sci. 103 321-1 329-
Mina, V.N. 1965. Leaching of certain substances by precipitation from woody plants and its importance in the biological cycle. Sov. Soil Sci. 6:609- 617.
Mitchell. C.P. 1990. Nutrients and growth relations in short-relation forestry. Biomass 22:9 2-1 05
Morrison, I.K. 1974. Dry-matter and element content of roots of several natural stands of pinus banksiana Lamb. In northern Ontario. Can. J. For. Res. 416 1 -64,
Morrison, I.K. 1973. Distribution of elements in aerial components of several natural jack pine stands in northern Ontario. Gan. J. For. Res. 3:170- 179.
Nair, P.K.R. 1 984. Soil productivity aspects of agroforestry. International Council for Research in Ag roforestry . Nairobi, Kenya.
Nambiar, E.K.S. and D.N. Fife. 1987. Growth and nutrient retranslocation in needles of radiata pine in relation to nitrogen supply- Ann. Bot. 60347- 156.
Nihlgard, B. 1972. Plant biomass, primary production and distribution of chemical elements in a beech and a planted spruce forest in South Sweden. Oikos 23169-81.
Ntayombya. P. and A-M-Gordon. 1995. Effects of black locust on productivity and nitrogen nutrition of intercropped barley. Agroforestry Systems 29:239-254-
Nye. P.H. 1971. Organic rnatter and nutrient cycles under moist tropical forest. Plant and Soil l3:333-346,
Ovington. J.D. 1962. Quantitative ecology and the woodland ecosystern concept. Adv. Ecol. Res- 1 :103-192.
Oyarzun, C.E., R. Godoy and A. Sepulveda. 1998. Water and nutrient fluxes
in a cool temperate rainforest at the Cordillera de la Costa in southern Chile. Hydrol. Process. 1 2: 1 067-1 077.
Paker, G.G. 1983. Throughfall and stemflow in the forest nutrient cycle. A d v . Ecol. Res, 13:57-133.
Pastor, J., J.O. Aber, C.E. McClangherty and J.M. Melillo. 1984. Aboveground production and N and P cycling along an nitrogen mineralization gradient on Blackhawk Island. Wisconsin. Ecology 65:256-258.
Perry, D.A. 1994. Throughfall and stemfiow, litterfall, dry deposition. In: Forest Ecosystems. pp.403-404, 362.393.
Reich, P.B. and M.B. Walters. 1994. Photosynthesis-nitrogen relations in Amazonian tree species. II. Variation in nitrogen vis-à-vis specific leaf area influences mass and area-based expressions. Oecologia 97:73-81.
Reich, P.B.. B.D. Kloeppel, D.S. Ellsworth and M.B. Walters. 1995. Different photosynthesis-nitrogen relations in hardwood and evergreen coniferous tree species. Oecologia 1 04:24-30.
Reiners, W.A. 1972. Nutrient content of canopy throiighfall in three Minnesota forests. OlKOS 23:14-22. Copen hagen.
Reiners, W.A. and R.K. Olson. 1984. Effects of canopy components on throughfall chemistry: an experimental analysis. OecoIogia (Berlin) 63:320-330.
Rhoades, C C , T.M. Nissen and J.S. Kettler. 1998. Soil nitrogen dynamics in alley cropping and no-till systems on ulisols of the Georgia Piedmont. USA. Agroforestry Systems 39:31-44.
Running, S.W.. D.L. Peterson, M.A. Spanner and K.B. Teuber. 1986. Remote sensing of coniferous forest leaf area. Ecology 57:273-276.
Santamaria, J.M., A. Martin- 1998. Influence of air pollution on the nutritional status of Navarra's forests, Spain. Chemosp here 36:943-948.
Santene, A., J.M. Mermal and V.R. Villenauva. 1990. Comparative tirne-course mineral conten study between healthy and diseased Picea trees from polluted area. Water, Air and Soil Pollution 52:157-174.
Satterlund. D.R. 1972. Wildland watershed management. Wiley, New York. 370pp.
Sharrna, S.C. and P.K. Pande. 1989. Patterns of litter nutrient concentrations in some plantation ecosysterns. For. Ecol. Manage. 29~151-163.
Sigmon. J.T., F.S. Gilliam and M-E-Partin. 1989. Precipitation and throug hfall chernistry for a montane hardwood forest ecosystem: potential contributions from cloud water- Can, J- For- Res- l9:1240-1247-
Simpson, LA., P.A. Wtlliams, W.C. Pfeiffer and A.M. Gordon. 1994. Biornass production on marginal and fragile agricultural lands: productivity and economics in southern Ontario, Canada- In: Schultz, R.C. and Collett. J.P. (eds.), Opportunities for Agroforestry In the Temperate Zone Worldwide: Proceedings of the Third North Agroforestry Conference, August 15-1 8. 1993, Department of Forestry, lowa State University, Ames. lowa, pp.397- 401.
Slapokas, T. and U. Granhall. 1 991. Decomposition of Iitter in fertilized short-relation forest on a low-humified peat bog. For. Ecol. Manage. 41:143-156.
Swank. W.T., and G.S. Henderson. 1976. Atrnospheric input of some cations and anions to forest ecosystems in North Carolina and Tennessee. Water Resources Res. 12:541-546,
Takagi M.. S. Sasaki, K-Gyokusen and A. Saito. 1997. Stemflow chemistry of urban Street trees. Environmental Pollution 96: 1 07-1 09-
Tang, C.Y. 1996. Interception and recharge processes beneath a Pinus elliotii forest. Hydrological Processes 10:1422-1434.
Thevathasan, N.V. and A.M.Gordon 1995. Moisture and fertility interactions in a potted poplar-barley intercropping. Agroforestry Systems 29:275-283.
Thevathasan, N.V. and A.M. Gordon 1997. Poplar leaf biomass distribution and nitrogen dynamics in a poplar-barley intercropped systern in Southern Ontario. Canada. Agroforestry Systems 003 -1 2.
Thevathasan, N.V. 1998. Some complementary interactions in tree-based intercropping systems in Southern Ontario. Ph.D. Thesis. Univ. Guelph. Canada. 21 3pp.
Tian, G. 1992. Biological effects of plant residues with contrasting chemical compositions on plant and soii under humid tropical conditions. Ph.D. Thesis. Wageningen University. The Netherlands.
Torrenueva, A.L. 1975. Variation in mineral flux to the forest floors of a pine and a hardwood stand in the Georgia piedmont. Ph.D. thesis, Univ. Georgia. Athens- 110 pp.
Ulrich. B., P. Benecke, W.F. Harris., et al. 1981. Soil processes. In Dynamic properties of forest ecosystems. Edited by D.E. Reichle. Cambridge University Press, Cambridge. England. pp.265-340.
Van Cleve, K., L. Oliver, R. Schlentner. L.A. Viereck and C.T. Dyrness. 1983. Production and nutrient cycling in taiga forest ecosystems. Can. J. For. Res. 1 31747-766.
Verry. ES. and D.R. Timmons. 1976. Precipitation nutrients in the open and under two forests in Minnesota- Can- J- For, Res- 7:112-119.
Vogt, K.A., Grier, CC. and Vogt, D.J. 1986. Production. turnover, and nutrient dynamics of above-and belowground detritus of world forests. Adv. Ecol. Res- 13303-377.
Voigt, G.K. 1960. Alteration of the composition of rainwater by trees. Am. Midl. Nat. 631321-326-
Voigt. G.K. 1960. Distribution of rainfall under forest stands. For. Sci. 6:2-9.
Vong, R.J., J.T. Sigmon and S.F. Mueller. 1991. Cloud water deposition to Appalachian forests. Environ. Sci. Technol. 25:1 014-1 021.
Waring, R.H.. A.J.S. McDonald, S. Larsson, Ti Ericsson. A. Wiren and E. Arwidsson. 1985. Differences in chernical composition of plants grown at constant relative growth rates with stable nutrient. Oecologia 66:157-160.
Wells, CD., H. L. Whigharn. 1972. Investigation of mineral nutrient cycling in upland Piedmont forest. J. Elisha Michel1 Sci. Soc- 88:66-78-
Whitford, W.G., J- Anderson and P-M- Rice- 1997. Stemflow contribution to the 'fertile island' effect in creosotebush, Larrea tridentata. Journal of Arid Environments 35:451-457.
WII, G.M. 1959. Nutrient return in litter and rainfall under some exotic-conifer stands in New Zealand. N.Z.J. Agric. Res. 2319-734-
Williams, P.A. 1993. The role of agroforestry in the stewardship of land and water. In: Webb, KT. (ed.) Proceedings of the Agroforestry Workshop, March 29-
30, 1993, Tniro, Nova Scotia, pp-80-88.
Williams. P.A. and A.M. Gordon. 1995. Microclimate and soi1 moisture effects of three intercrops on the tree rows of a newly-planted intercropped plantation. Agroforestry Systems 29:288-302.
Williams, P.A. and A.M. Gordon. 1992. The potential intercropping as an alternative land use system in temperate North Amenca- Agroforestry systems 19:253- 263.
Wyttenbach, A., P. Schleppi, L-Tobler. S. Bajo and J. Bucher. 1995. Concentrations of nutritional and trace elementç in needles of Norway spnice (Picea abies p.] Karst) As function of the needle age class. Plant and Soil 168-1 69:305-312-
Young, A. 1989. Agroforestry for soi1 conservation. CAB International, Wailingford. U K,
Young, J.L. 1964. Ammonia and ammonium relations with some Pacific Northwest soils. Soil Sci. Soc- Am- Proc- 28:339-345.
Zhang, W.R., B.T. Xu, C.D. Yang, B. Li and X.N. Tu. 1990. Studies on structure and function of forest floors of mountain forest soils- ACTA PEDOLOGICA SINICA 27:12l-l3f.
Zinke, P.J. 1962. The pattern of influence of individual forest on soi1 properties. ECOIO~Y 4311 30-1 33-
6. APPENDICES
Appendix 1. Seasonal patterns of throughfal1 for various nutrients in an
intercropping system in Southern Ontario, Canada 1997-1 998.
Appendix 2. Seasonal patterns of stemfiow for various nutrients in an
intercropping system in Southern Ontario, Canada 1997-1 998.
Appendix 3. Modelling nutrient inputs in an intercropping situation in Southern
Ontario, Canada-
Appendix 1. Seasonal patterns of throughfall for various nutrients in an
intercropping system in Southern Ontario, Canada 1997-1998- .
Figure 6.3 through 6.3 show the seasonal pattens of phosphoms, nitrate and
ammonium fluxes in throughfall under different tree species. The nutrient fluxes
from event to event varied strongly (pc0.05) for al1 three elements.
The values of 0-20 on figure 6.1,6.2 and 6.3 represent the dates which are:
1-July 15, 1997 2-July 21, 1997 3-J~ ly 28, 1997 4- AU^. 14, 1997
5Aug. 16. 1997 6-Aug. 21, 1997 7Aug. 28, 1997 8-Sept. 7, 1997
9-Sept. 1 1, 1 997 10-sept. 20. 1997 1 1 -Sept. 26, 1 997 12-0ct.24. 1997
13-oct. 29, 1997 1CNov. 4. 1997 15-May 31,1998 16-June 3,1998
17-June 12,1998 18-June 17,1998 19-June 24,1998 20-June 30,1998
- - ranfal -+ - walnut ' - oak maple ::
-poplar -*-ash l
I
Date
Figure 6.1. Temporal changes in phosphorus fluxes in throughfall passing through the vanous tree species at the intercropping system.
--.--- rainfall - - walnut
oak - e- maple --- poplar - -0 - ash
O 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Date
Figure 6.2- Temporal changes in nitrate fluxes in throughfall passing through various tree species at the intercropping system
84
1 --*-- rainfaii - wainut I
- oak -=- maple / \ -+ poplar -- - ash
O 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Date
Figure 6.3. Temporal changes in ammonium fluxes in throug hfall passing through vanous tree species at the intercropping system
Appendix 2. Seasonal patterns of stemflow for various nutrients in an
intercropping system in Southern Ontario, Canada 1997-1 998.
Figure 6.4 through 6.6 show the seasonal pattens of nutrient fluxes of
p hosp horus, nitrate and ammonium from stemflow under different tree species. The
nutrient Ruxes from event to event varied strongly (Pc0.05) for al1 three elements.
The significant differences (pç0.05) were presented in stemflow fluxes across tree
species-
The values of 0-20 on figure 6.4, 6.5 and 6.6 represent the dates which are:
1-JUIY 15, 1997 2-JUIY 21. 1997 3-July 28, 1997 4- AU^. 14, 1997
5-Aug. 16, 1997 6-Aug. 21, 1997 7Aug. 28, 1997 8-Sept 7, 1997
9-Sept.11, 1997 10-sept 20, 1997 1 1 -Sept. 26, 1997 12-0ct. 24, 1997
13-oct. 29,1997 14-NOV. 4, 1997 15-May 31,1998 16-June 3,1998
17-June 12,1998 18-June 17,1998 19-June 24,7998 20-June 30, 1998
. walnut oak maple p o p l a r
-.,- ash
O 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 1 f 18 19 20
Oate
Figure 6.4- Temporal changes in phosphorus fluxes in stemflow under various tree species a t the intercropping system
- , . walnut oak maple poplar
-..-. ash
Date
Figure 6.5. Temporal changes in nitrate fluxes in stemflow under various tree species at the intercropping systern
-., . - walnut oak a
C 0-1 - , . maple - poplar QI -..-- ash
Date
Figure 6.6. Temporal changes in ammonium fluxes in stemflow under various tree species at the intercropping system
Appendix 3. Modelling nutent inputs in an intercropping situation in Southern Ontario, Canada-
Comparison of Soil Organic Matter compononts in an Intercropping System and a Monocropping System Using the CENTURY Model
ABSTRACT
This study compares the SOM regime (dynamics of SOM residue, SOM
carbon, SOM nitrogen) in intercropping and monocropping systems using the
CENTURY mode1 as an evaluation tool. The results show that the SOM residue in
an intercropping system is 4 times the amount in a monocropping system; SOM C
in an intercropping system is 2 times the amount in a mûnocropping system. Total
N input in an intercropping systern is also more than monocropping system, while
mineral N leaching in stream flow is lower.
Key Words: lntercropping system. monocropping system. SOM residue. SOM
carbon, SOM nitrogen
INTRODUCTION AND LITERATURE REVIEW
Soil organic matter (SOM) plays an important role in nutrient cycling and soi1
productivity in al1 ecosystems. SOM is a major agent that stabilizes aggregates and
can be adequately described by three different p o o k an active pool (microbial
biomass), a slow pool and a passive pool. The amount and stability of soi1 organic
matter depends on how much organic matter entes the soil each year and how fast
this organic matter decomposes in the soil (Parton et al., 1987: Voroney et al.,
1995). Decomposition, turnover and the biochemistry of soi1 organic matter are
affected by different cropping systems. lntercropping is considered an excellent
land-use system because of its productivity, sustainability and adoptability (Nair,
1993; Williams and Gordon, 1997). The purpose of this study was to compare soi1
organic matter between intercmpping practices and monocropping practices, using
the CENTURY rnodel.
The CENTURY mode1 developed by Parton et al. (1 987) has been used to
analyse the short-term effects of management on soi1 organic rnatter in Quebec,
Canada, and to sirnulate management practices, crop production and soi1 organic
matter dynamics at each field site (Voroney et al. 1995). The CENTURY model can
simulate the impacts of climate and farm management effects on prirnary
productivity, C, N, P. and S dynamics and soi1 water balance in agroecosysterns.
al1 of which centre around soi1 organic matter dynamics (Parton et al., 1983, 1987,
1988; Paustian et al., 1992; Carter et al., 1993; Probert et al., 1995; Vallis et al.,
1996). The CENTURY model has also been used to evaluate the impact of
alternative farrn management practices on nitrogen pollution of ground water in
southwestern Ontario. It can be used to gain insights into the effect of fertilizer
management, tillage treatment, crop choice, and multi-crop rotation effects on N
90
leaching and on crop yields (Yiridoe et al., 1997) and has been used to analyse the
interactions between organic matter addition, fertilization, and crop productivity
(Paustian et al., 1992).
MATERIALS AND METHODS
Study Site
The field site was located at Agroforestry Research Station. University of
Guelph, in southern Ontario (43' 32' 28" N, 80 92' 3 2 W). Mean annuai
precipitation at the site is 836mm yr' and the mean annual temperature is 6.65 OC.
The soi1 is a sandy clay loam with a clay content of 35% (Brunisolic Gray Brown
Luvisol).
The site had been used for continuous production of hay prior to initiating
the intercropping study in 1987. Annual crop production had been declining and soi1
erosion was becorning serious. Since 1987, trees (mostly broad leaf tree species)
have been planted into this site with row spacing of 12.5m or 15m between crops;
three crops have been grown on the site using a corn - soybean - winter wheat
rotation.
Treatment and Management Description
The treatments of this study were: (1) monocropping - continuous hay
production was simulated over 20 years from 1965 to 1985, then the rotations of
91
corn-soybean- winter wheat were simulated over 30 years from 1986 to 201 5.
(ii) intercropping - continuous bariey production were simulated over 20 years from
1965 to 1985, then the intercropped, broad leaf trees and the rotations of corn-
soybean- winter wheat. were simulated over 30 years from 1986 to 2015. To be
constant. the growing season for al1 crops and trees was detemined to be from
April to September, and 50% straw from crops was removed from study site every
year. 100% of the deciduous tree leaves fall at the end of the growing season.
Fertilization (medium) and cultivation (plow) were carried out once a year,
respectively, in each of the 50 simulation years.
The CENTURY model
The CENTURY model is a general model that has been used extensively to
describe the SOM dynamics for different ecosystems. The CENTURY mode!
enables the user to simulate several different land uses and allow for a wide variety
of management options (Motavalli et al. 1994). The model is used for predicting site
productivity and soi1 dynamics over periods in excess of those available for field
experimentation. Results have shown that the modei accurately simulated total soi1
organic carbon, nitrogen dynarnics, and net primary productivity (NPP) across a
wide range of managed and natural tropical ecosysterns (Parton et al. 1994).
The model is broken down into three soi1 organic pools (active, slow and
passive), which have different associated below and aboveground Iitter pools,
decornposition rates and a surface microbial pool which is associated with
92
decomposing surface Iitter (Metherell et al. 1 993).
In the execution process of the CENTURY 4.0 model there are 5 main
stages:
1. File1 00 - User inputs the data for their specific site
2. Eventl00 - User plans the events to occur over time
3. CENTURY execution
4. List1 00 - User identifies variables for output
5. Reading output - User exports data to graphical software (e-g., Excel)
Parameterization
The CENTURY model functions on a rnonthly time-step that requires:
-monthly average max and min air temperature
-monthly precipitation
-soi1 texture
-plant nitrogen, phosphoros, and sulfur
-1ignin content of plant material
-atrnospheric and soi1 nitrogen inputs
-initial soi1 carbon, nitrogen, phosphoros and sulfur
Wherever information was unavailable, the data from the Elora research
station, 15 km away from the study site was used to fiIl the gaps.
Site-specific parameters, crop parameters and initial conditions such as soi1
93
texture, bulk density, soi1 depth, pH, total soi1 C and N content, initial mineral values,
monthly precipitation and mean maximum and minimum monthly temperature were
obtained from the field site at EIora Research Station, University of Guelph in
southern Ontario. Tree parameters are based on fked values that are set in the
Tree. 1 00 file-
RESULTS AND DISCUSSION
The different cropping systems (intercropping and monocropping) resulted
in changes to soi1 organic matter residue, soi1 organic matter carbon and soi1
organic nitrogen using the CENTURY model.
Soil Organic Matter Residue Dynamics
SOM residue dynamic is a useful indicator for turnover of organic matter in
both intercropped and monocropped soil. The SOM residue in the surface of the
intercropping system stays at 450 kg ha-' from 1 990 to 201 5. Meanwhile, it is 250
kg ha-' in the monocropping system. The SOM residue in the soi1 of the
intercropping system keeps increasing from 1987 to 2015 and amounts to 2.5 t ha-'
in 2015. In monocropping system, it is 0.6 t ha". The SOM residue in soi1 in the
intercropping system is 4 times the amount of the monocropping system.
Soil Organic Matter Carbon Dynamics
94
Table 6.1. Carbon pools and fluxes in intercropping and monocropping systems.
Carbon parameters lntercropping Monocropping
annual C input 1-5 t ha-' 0-8 t ha-'
litter structural C in surface 280 kg ha-' 120 kg ha-'
litter structural C in soi1 2-5 t ha-' 0-5 t ha"
C in active SOM in surface 120 kg ha-' 27 kg ha-'
total C including belowground 45 t ha-' 32 t ha''
surn of C in wood components 4.7 t ha-' O t ha-'
total C in forest sysiem 70 t ha-' 35 t ha"
C from organic leaching of stream flow 0.2 kg ha-' 0.1 kg ha-'
annual CO, respiration 1 -7 kg ha" yr -' 1.0 kg ha-' yr -' annual accumulator for CO, loss 300 kg ha-' yr -' 200 kg ha-' yr -'
Table 6.2. Ntrogen pools and fluxes in intercropping and monocropping systems.
Nitrogen parameters lntercropping Monocropping
total N 4 t ha-' 3.8 t ha"
litter structural N 1.4 kg ha-' 0.5 kg ha-'
N in active SOM 8 kg ha-' 2.2 kg ha-'
N from mineral leaching of strearn flow O g ha-' 1.5 g ha-'
SOM carbon is the main component of SOM. SOM carbon dynamics
represent the biological and biochemical process of decomposition, accumulation
and turnover of SOM, There are marked differences of SOM carbon dynamic
between intercropping and monocropping systems Fable 1).
The annual C input in the intercropping system from 1990 to 2015 was
constant at 1.5 t ha-' and in the monocropping system 0.8 t ha". Litter structural C
content in the surface of the intercropping system is constant at 280 kg ha" from
1990 to 201 5, and in the monocropping system 120 kg ha''. Litter structural C in
soi1 from the intercropping system is increasing from 1990 to 201 5. amounting to 2.5
t ha-' in 201 5; in the monocropping system, it decreases, and is 0.5 t ha" in 201 5.
This is a 5-fold difference. C in the active SOM in the surface of the intercropping
system increases from 1990 to 2015 and amounts to 120 kg ha"; in the
monocropping system, it is only 27 kg ha-'. C in passive SOM in both the
intercropping and monocropping systems decreases slightly. Total soi1 C including
belowground structural and metabolic components in the intercropping system
increases slightly from 1990 to 2015 (45 t ha-'), and in the monocropping systern
decreases (32 t ha-') (Fig. 6.7. 6.8). The sum of C in wood components in the
intercropping system increases from 1990 to 2015 (4.7 t ha-'), and remains at zero
in the monocropping system (O t ha") since there is no organic rnatter input source
from trees in this system. The total C (Le. sum of soi1 organic matter, trees dead
wood, forest litter) in the intercropping system increases from 1988 to 2015 and
amounts to 70 t ha-'; in the monocropping system, it decreases slowly from 1988
96
Fie- 6-7. Total soi1 C in intercropping system
.- - -, - --
1960 1970 $980 f 990 2000 2010 2020
1 ime
Fig. 6.8. Total soi1 C in monocropping system
1990 2000
Time
to 2015 (35 t ha-'). C from organic leaching in stream fiow in the intercropping
system increases slowly from I W O to 201 5 and arnounts to 0.2 kg ha-' in 201 5;
in the monocropping system. it decreases to 0.1 kg ha-'.
Soil respiration is an indicator of intensity of biological activity. Annual CO,
respiration from decomposition in intercropping systern increases from 1990 to 201 5
and amounts to 1 -7 kg ha-' yr' ; the in
ha-' yrl. The annual accumulator for
SOM decornposition in intercropping
monocropping system. it decreases to 1.0 kg
CO, loss due to microbial respiration during
system increases slowly frorn 1 990 to 201 5,
and amounts to 300 kg ha-' yr'; in the monocropping system, it decreases to 200
kg ha-' yr'.
Soil Organic Matter Nitrogen Dynarnics
SOM N also is a main component of SOM. SOM N dynarnics represent the
biological and biochemical processes for assimilation, mineralization. nitrification
and imrnobilization of SOM- There are marked differences in SOM N between
intercropping and monocropping systems (Table 2).
The total N in the intercropping system was constant (4 t ha-') from 1990 to
201 5. and in monocropping system decreased slowly to 3.8 t ha-' (Fig. 6.9. 6.1 0).
Structural N in litter in the intercropping systern increased from 1990 to 201 5 and
amounted to 1.4 kg ha-'; in themonocropping systern. it decreased to 0.5 kg ha-'.
N in active SOM in the intercropping system increases from 1990 to 2015 and
amounts to 8 kg ha", and in the monocropping system decreases to 2.2 kg ha-'. N
98
Fig. 6.9- Total soi1 N in intercropping system
O 1960 1970 1980 1990 ZOO0 2010 ZOZO
Tim e
Fig. 6.10. Total soi1 N in monocropping system
1960 1970 1980 1990 2000 2010 2020
Tim e
in passive SOM in both intercropping and monocropping systems decreases. N
from organic leaching in stream flow in the intercropping system is constant at 20
g ha*'. N from mineral leaching stream flow Ri the intercropping system goes to zero
in 1990 and remains in constant until 2015; in the monocropping system, the
mineral N leaching of stream flow is retained at 1.5 g ha-'. The study shows that
trees in an intercropping system can be used to remedy N contamination from
agricultural systems. improving water quality and protecting environment.
CONCLUSION
From a comparison of SOM residue. SOM carbon and SOM nitrogen. the
SOM regime in intercropping system has clear superiority. The SOM residue is 4
tirnes the amount of the monocropping system. the SOM carbon is double and the
SOM nitrogen is more while at the same time the minera1 N in stream flow is lower.
ACKNOWLEDGEMENTS
I would Iike to thank Dr. R. Paul Voroney and Dr. Andrew M. Gordon for their
helpful comments.
REFERENCES
Carter. M-R-, W-J- Parton, 1-C. Rowland, J-E-Schultz, and GR. Steed. 1993. Simulation of soi1 organic carbon and nlrogen changes in cereal and pasture systems of southem Australia. Aust. J. Soil Res. 31 :481-491.
Metherell, A.K., LA. Harding, C.V. Cole and W.J. Parton. 1993. CENTURY soil organic rnatter model environment. Colorado State Univ., USDA-ARS, Fort Collins, Colorado. iv+65p-
Motavalli, P.P.. C.A. Palm. W.J. Parton, E.T. Ellot and S.D. Frey. 1994. Cornparison of laboratory and modelling simulation methods for estimating soi1 carbon pools in kopical fores? soil. Soil Biol. Biochem. 26~935-944-
Nair, P.K.R. 1 993. An Introduction to Agroforestry. Kluwer Academic. Dordrecht, The Netherlands,
Parton, W.J.. D.S. Schimel, C.V. Cole, and D.S. Ojima. 1987. Analysis of factors controlling soi1 organic matter levels in Great Plains grasslands. Soil Sci. Soc- Am. J- 51 ~1773-1179.
Parton, W.J.. D.W. Anderson, C.V. Cole and J.W.B. Stewart. 1983. Simulation of soi1 organic matter formations and mineralization in semiarid agroecosystems. In ER. Lawrence et al. (ed.) Nitrogen cycling in agricultural systems. Spec. Publ. 23. The University of Georgia, College of Ag riculture Experirnent Stations.
Parton, W.J., J.W.B. Stewart, and C-V. Cole. 1988. Dynamics of C, N, P, and S in grassland soil: A model. Biogeochemistry. 5: 109-1 31.
Parton, W.J. J.M.O. Scurlock, DSOjima, T.G. Gilmanov, R.J. Scholes, D.S. Schimel. T-Kirchner, J-C. Menaut. T. Seastedt. E. Garcia Moya, A. Kamnalrut, and J.L. Kinyarnario. 1994. Observations and modelling of biomass and soi1 organic matter dynamics for the grassland biome worldwide. Global Biogeochem. Cycl. 7:785-809-
Paustian. K., W.J. Parton, and J. Persson. 1992. Influence of organic amendments and N fertilization on soi1 organic matter in long-terni plots: Model analyses. Soil Sci. 56:476-488.
Probert, M.E.. B.A. Keating, J.P. Thompson, and W.J. Parton. 1 995. Modelling
experiment. Aust. J. Exp. Agric. 35:941-950.
Vallis 1.. W.J. Parton, B.A. Keating, and A.W. Wood. 1996. Simulation of the effects of trash and N fertilizer management on soi1 organic matter levels and yields of sugarcane. Soil Tillage Res. 38:115-132.
Voroney, R.P., Denis A. Angers. 1995. Analysis of the short-term effects of management on soi1 organic matter using the CENTURY model. In: R. Lal. John Kirnble, Elissa Levine. BA. Stewart.. Soil management and greenhouse effect, Chapter 10. 11 3-1 20. LEWIS PUBLISHERS.
Williams, P.A. and A. M. Gordon. 1997. Agroforestry in North America and its role in farrning systems. In: Gordon, A.M. and S.M.Newman (eds.) Temperate Agroforestry systems pp.9-21, 35-48.
Yiridoe. E.K.. R. Paul Voroney. and Alfons Weersink. 1997. Impact of Alternative farm management practices on nitrogen pollution of groondwater: Evaluation and Application of CENTURY model. J. Environ. Qual. 263255-1263-