Biodiversity and Conservation 12: 975–990, 2003. 2003 Kluwer Academic Publishers. Printed in the Netherlands.

The influence of stand age on wildlife habitat use inexotic Teak tree Tectona grandis plantations

1,2, 1,3*RICHARD K.B. JENKINS , KIRSTEN ROETTCHER and GRAHAM1CORTI

1 2Society For Environmental Exploration, 50-52 Rivington Street, London EC24 3QP, UK; Currentaddress: Zoology Building, School of Biological Sciences, University of Aberdeen, Aberdeen AB24 2TZ,

3UK; Current address: Saadani Conservation Development Programme, c /o GTZ, P.O. Box 1519, Dar*es Salaam, Tanzania; Author for correspondence (e-mail: r.jenkins@abdn.ac.uk; fax: 144-1224-

272396)

Received 25 January 2002; accepted in revised form 15 May 2002

Key words: Flood plain, Habitat structure, Mammals, Miombo, Plantations, Tanzania, Teak

Abstract. Tropical dry woodlands provide important natural resources for both humans and wildlife, butwoodlands situated outside protected areas are vulnerable to over-exploitation. In the Kilombero Valley,Tanzania, miombo woodland is converted into teak plantations and small, private farms, but the impact ofthis habitat change on wildlife populations is poorly understood.We assessed the frequency of habitat useof large mammals in teak plantations of different age during the wet season. Vegetation structure variedsignificantly with age; older plantations had larger trees, a more extensive shrub layer and a well-developed leaf litter. Younger plantations had smaller trees and larger areas of short vegetation and bareground. Track surveys revealed that older plantations were predominantly used by bush pig Potamoch-oerus larvatus, bushbuck Tragelaphus scriptus and duiker (Cephalophus harveyii, C. natalensis orSylvicarpa grimmia), whilst the younger plantations were used by open-habitat specialists such aswarthog Phacochoerus africanus and waterbuck Kobus ellipsiprymnus. Proximity to the flood plain wasalso found to be important and plantations nearest this area contained significantly more tracks of largegrazers and bulk feeders, reflecting use by zebra Equus burchelli, buffalo Syncerus caffer and waterbuck.Areas of miombo woodland that have been converted into teak plantations provide suitable habitat forwildlife in the Kilombero Valley, but their conservation value diminishes with time. Future managementshould therefore aim to maintain the patchwork of miombo woodland and teak plantations in order toprovide suitable habitat for a range of wildlife. Where possible, teak plantations should not be situatedclose to the boundary of the miombo woodland and flood plain because this habitat is an important wetseason refuge for wildlife during the wet season.

Introduction

Tropical dry woodlands are declining in Africa because of the increasing demandfor natural resources by people (Abbot and Homewood 1999). In Tanzania, many ofthe remaining areas of miombo woodland occur outside the protected area networkand are threatened by fuel wood extraction and conversion to different forms ofagriculture, such as crop farms, rice fields and forestry (UNEP 1998). Althoughforestry is less of a contributor to woodland loss on a national scale (UNEP 1998),localised plantation developments may be detrimental to wildlife.

The effect of forestry monocultures on biodiversity and wildlife populations has

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been extensively investigated and most previous research falls into one of twocategories: (1) comparisons of populations between plantations and nearby naturalhabitats (e.g. Lugo 1992; Chandrasekar-rao and Sunquist 1996; Lindenmayer et al.2000; Hinde et al. 2001a, b) and (2) comparisons of animal populations betweenplantations in different successional stages (e.g. Baguette et al. 1994; Fernandez etal. 1994; King et al. 1996; Latham et al. 1996). Most of this research has involvedbirds (e.g. Allan et al. 1997; Datta 1998; Hayes and Samad 1998; Kwok and Corlett2000) and small mammals (e.g. Fernandez et al. 1994; King et al. 1996; Decher andBahain 1999; Sullivan et al. 1999). Fewer studies have investigated the use of forestplantations by large mammals and most of these studies have been undertaken in thetemperate regions (e.g. Gill et al. 1996; Latham et al. 1996). By comparison, habitatuse by large mammal communities in tropical forest plantations has been under-studied, although Zanne et al. (2001) recently demonstrated the role that pineplantations could play in maintaining large mammal communities in Uganda.

Forestry monocultures can make significant contributions to the economy ofdeveloping countries, but they are always associated with a cost to the environment.In Tanzania, although forestry plantations constitute a small percentage of the landused by agricultural monocultures (UNEP 1998), they could have significantnegative impacts on the local environment. The survival of many large mammalpopulations outside protected areas in Tanzania is threatened by expanding humansettlements and increases in agricultural activities, such as crop farming, cattle andforestry (Mwalyosi 1991; East 1998; Caro 1999). In areas that are currentlyundergoing conversion from natural habitats to forest plantations it is important tounderstand the effect of aforestation with alien species. In light of this, we havemonitored the impacts on wildlife of a new teak Tectona grandis plantationdevelopment in the Kilombero Valley (Hinde et al. 2001a, b; Jenkins et al. 2002).

Although the Kilombero Valley Teak Company (KVTC) plans to convert only ca.10000 ha of the valley’s ca. 280000 ha into teak, there are concerns based on theloss of natural habitat for wildlife and the location of plantations in environmentallysensitive areas (IIED 1992). For example, plantations located close to the flood plaincould reduce the amount of wet season habitat available and may open up areas tofarmers and poachers.

The Kilombero Valley is home to important populations of large mammals (Table1) and is estimated to hold approximately 75% of the remaining population of pukuKobus vardoni (East 1998; TWCM 1999). Herbivores such as elephant Loxodontaafricana, buffalo Syncerus caffer and zebra Equus burchelli move from the floodplain grasslands into the miombo woodland foothills during the wet season(UDDNR 1997; Jenkins et al. 2002). The management practices used to maintainteak stands, which include clearing, burning, planting, weeding and thinning, arelikely to have a profound impact on the plantation vegetation structure and in turn,on wildlife populations. The oldest teak plantations at the time of study were 7 yearsold, but new areas of miombo woodland are cleared and planted annually. We havepreviously described the large mammals in teak, miombo and evergreen forest in theKilombero Valley (Hinde et al. 2001a), but the effect of variation in habitat structurewithin plantations has not yet been addressed. Therefore this study aims to

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Table 1. Population estimates (6se) of large mammal species in the KGCA during October 1998(TWCM 1999).

Species Population estimates (6se)

Elephant 5308 6 2151Buffalo 16778 6 12006Reedbuck Redunca spp. 520 6 495Puku 66964 6 12629Zebra 631 6 449Hippo Hippopotamus amphibious 1262 6 755

contribute to the environmentally responsible management of the teak plantations bycomparing large mammal use in stands of different ages.

Study site and methods

Study site

The Kilombero Valley adjoins the Selous Game Reserve and is close to MikumiNational Park (Figure 1). The inner part of the Kilombero Valley is partiallyprotected as the Kilombero Game Controlled Area (KGCA) and consists of aseasonal flood plain that is fringed by tracts of miombo woodland and farmlandrising to old block mountains with evergreen forest patches. The rainfall in thevalley is largely unimodal with an annual mean between 1200 and 1400 mm (IIED1992). The wettest period of the year is between March and May.

The teak plantations are situated in four blocks consisting of small plantations(,50 ha) of different ages, two north of the Kilombero River and two to the south(Figure 2). Teak stands planted in 1993/1994, 1996/1997 and 1998/1999 wereselected from the Mafinji block to represent the range of plantation ages found in theKilombero Valley. Using maps provided by KVTC, plantations located at a range ofdistances from the edge of the flood plain (6–13 km) were included. Plantation sizewas similar across age groups and ranged from 5.1 to 11.7 ha. Mean plantation sizefor 1993/1994 plantations was 8.56 6 0.72 ha (n 5 5), for 1996/1997 it was 8.71ha 6 0.51 (n 5 9) and for 1998/1999 it was 9.07 6 0.98 (n 5 6).

Plantations were visited in January and February 2000 to collect information onthe structure of teak plantations and again during April 2000 to survey animal tracksand describe the vegetation. The chronosequence study design was used (Twigg etal. 1989), which uses a range of successional stages instead of monitoring planta-tions through time (Fernandez et al. 1994).

Vegetation surveys

Five replicate vegetation surveys were conducted for each plantation age. Transectlines, consisting of 100 m ropes, were laid out perpendicular to and 10, 30, 50, 100

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Figure 1. Sketch map showing the location of the KGCA, Mikumi National Park and the Selous GameReserve in Tanzania. Tributaries of the Rufiji are represented by letters; A 5 Luhumbero river, B 5

Ruaha river, C 5 Kilombero river.

2and 150 m from the plantation edge. Quadrats (3 3 3 m ) were placed on theleft-hand side of the line every 20 m. The following measurements were taken:1. Teak tree dispersion: the distance (cm) to the nearest five mature teak trees from

the bottom right-hand corner of the quadrat.2. Diameter at breast height (dbh): measured from the five nearest teak trees to the

quadrat with a dbh tape.3. Teak tree height: measured using the isosceles triangle method (Philip 1983).4. Leaf litter depth: 10 measurements were taken in each quadrat by placing a

calibrated stick into the leaf litter.2 25. Leaf litter mass: a 1 3 1 m sub-plot was randomly selected in the 3 3 3 m plot

and all the leaf litter was removed and weighed in situ.

Information on the percentage cover of the main vegetation components was also2assessed. Quadrats (1 3 1 m ) were placed at 20 m intervals on the 100 m animal

track transect line, giving six estimates of percentage cover per line. Percentagecover was estimated for the following categories: tall vegetation (.1.0 m), mediumvegetation (0.10–0.99 m), short vegetation (,0.10 m), bare ground, burnt groundand leaf litter.

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Figure 2. Sketch map of the study area showing the boundaries of the four areas leased by the KVTC.Filled areas represent areas already converted into teak plantations.

Mammal surveys

Mammal tracks were surveyed using 100 m line transects located in 20 teakplantations. A total of 90 transects were surveyed, 30 in each teak age group.Transect lines were laid out in a random direction every 300 m and care was takennot to disturb the conditions underfoot when setting the lines. Each line wascarefully searched for animal tracks by two experienced observers 1 m on either sideof the line. District Game Office scouts (listed in Acknowledgements) identified all

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tracks. A relative track score was used to estimate habitat use based on the presenceor absence of tracks in each of the five 20-m sections on a transect. Scores thereforeranged from 0 (no tracks) to 5 (tracks present in each section) for each species ineach transect. This approach allowed a rapid assessment of each transect without theneed to count every track.

Field identification of small antelopes from tracks can sometimes be difficult. Insome cases, the tracks and signs could have come from one or more closely relatedspecies. For example, it was not possible to determine whether the duiker trackswere from Harvey’s red duiker Cephalophus harveyii, Natal red duiker C. natalensisor from common duiker Sylvicarpa grimmia, as all have been recorded from theSelous ecosystem (UDDNR 1997; East 1998). For the purpose of this study wegrouped all duiker together because differences between ecologically distinct groupswere more important than differences between closely related species.

The distance of each teak plantation to the flood plain was measured with ahand-held GPS (Garmin 48). We used the village of Madabadaba, which is on theedge of the flood plain, as the reference point. Plantations were classed into threedistance categories: near (6.8 km from Madabadaba), middle (8.8–10.3 km) or far(11.7–12.6 km).

Data analysis

To overcome small sample sizes, all herbivores were classified into a trophic groupbased on their feeding ecology (Hinde et al. 2001a). This produced four maingroups: grazers (waterbuck Kobus ellipsiprymnus, sable Hippotragus niger andeland Tragelaphus oryx), bulk feeders (buffalo, zebra and elephant), gleaners(duiker and bushbuck Tragelaphus scriptus) and rooters (warthog Phacochoerusafricanus and bush pig Potamochoerus larvatus). Statistical comparisons were alsomade for individual species with a sample size .30 (i.e. warthog, waterbuck, bushpig, buffalo, duiker and bushbuck). In all cases, individual transect lines weretreated as independent replicates.

Principal component analysis (PCA) was used to summarise the percentage coverdata. The resulting principal components (PCs) represented parametric habitatvariation between sites on axes that accounted for inter-correlations of the habitatvariables. The scores of the main PCs were then related to track abundance usingcorrelation. ANOVA and post hoc tests were used to compare habitat characteristicsand track abundance between ages. Vegetation data were analysed using non-parametric statistical tests.

Results

Vegetation surveys

Dbh, tree height, leaf litter depth and leaf litter weight were all significantly differentbetween teak plantations of different ages (Table 2). Measurements increased with

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Table 2. Statistical comparisons and median (1 range) of percentage cover and vegetation structure inteak plantations of different ages in the Kilombero Valley, Tanzania (H values from Kruskal–Wallis test).

Planting date

1993/1994 1996/1997 1998/1999 H

Percentage vegetation coverTall 75.4 56.0 17.5 24.7*

(16.7–98.0) (14.0–89.0) (0.0–63.0)Medium 22.1 30.0 31.5 0.6

(2.7–74.7) (8.0–77.0) (11.8–67.5)Short 4.5 8.0 8.0 6.8*

(0.0–25.8) (1.0–18.0) (0.0–55.0)Burnt 0.0 1.0 4.9 9.1*

(0.0–1.8) (0.0–24.0) (0.0–16.0)Leaves 80.0 42.0 27.1 8.9*

(15.3–100.0) (17.0–87.0) (7.0–74.0)Bare ground 72.5 36.0 38.0 3.8

(0.0–99.0) (1.0–93.0) (1.6–96.0)Vegetation structureDbh (cm) 11.4 7.3 1.6 87.7*

(0.6–37.4) (0.5–28.0) (0.1–18.8)Dispersion (cm) 3.0 2.9 2.9 3.4

(1.6–13.9) (1.0–11.25) (1.0–19.53)Tree height (cm) 8.5 6.4 1.2 41.7*

(0.2–14.3) (0.6–11.0) (0.2–4.21)Litter depth (cm) 6.2 4.6 0.7 120.5*

(1.1–22.5) (0.2–11.1) (0.3–2.3)Litter weight (g) 4225.0 230.0 50.0 72.0*

(5.0–1690.0) (5.0–1360.0) (5.0–1640)

*P , 0.05.

the age of the plantation, with the exception of the mean distance between trees. Theyoungest plantations (1998/1999) were therefore characterised by small, thin treesand a poorly developed leaf litter. The oldest plantations (1993/1994) were at theopposite end of the gradient and were characterised by thicker, tall teak trees, ashrub layer and a deep leaf litter.

The percentage cover estimates of tall and short vegetation, burnt ground and leaflitter were significantly different between the teak plantations (Table 2). The1998/1999 teak was characterised by short vegetation and patches of burnt vegeta-tion. The 1996/1997 teak had taller vegetation and more leaf litter than the1998/1999 teak. The oldest teak in the 1993/1994 plantations had tall vegetationand an extensive leaf litter.

Principal component 1 (PC 1) accounted for 36% and PC 2 for 20% of thevariation in the habitat data. The positive end of PC 1 represented areas of tallvegetation with high leaf cover and bare ground. The negative end represented areasof short and medium vegetation. The positive end of the PC 2 axis represented areasof bare ground with short vegetation. The negative end represented areas of mediumvegetation with a high leaf litter. Essentially, these two axes described a gradientfrom old plantations to young plantations. PC 1 scores were significantly different

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between the three teak age groups (ANOVA F 5 53.8, P , 0.01), but PC 22,90

scores showed no statistical difference (F 5 0.8, P . 0.05) and therefore only2,90

PC 1 scores were subsequently related to track abundance.

Mammal surveys

The abundance of tracks from all four trophic groups was significantly differentbetween teak age groups with post hoc tests revealing most significant differencesbetween the youngest (1998/1999) and oldest (1993/1994) plantations (Figure 3).With the exception of the gleaners, evidence of all other trophic groups was mostabundant in the youngest plantations (Figure 3). The significant linear relationshipbetween track abundance and PC 1 shows similar results (Figure 4a–d). Meanspecies richness was also lowest in the 1993/1994 teak (2.43) and highest in the1996/1997 and 1998/1999 plantations (3.03 in both).

The abundance of bushbuck and duiker tracks was significantly different betweenteak plantation ages with track scores the highest in the 1993/1994 plantations(Figure 5a and c). Bush pig tracks showed a similar, but statistically insignificanttrend (Figure 5b). The abundance of warthog tracks was also significantly differentbetween plantation ages, with evidence of warthogs most common in the old1993/1994 teak (Figure 5f). Therefore, although warthog and bush pig were classedin the same trophic group, they exhibited different habitat selection. Buffalo trackswere recorded from all teak age groups, but youngest teak contained significantlymore tracks than the old teak (Figure 5e). The abundance of waterbuck tracks was

Figure 3. Mean abundance (1 se) of tracks for four large mammal tropic groups in teak plantations ofthree different ages from the KilomberoValley, Tanzania. Grazers F 5 4.91, P 5, 0.05; bulk feeders2,88

F 5 8.82, P 5 , 0.01; gleaners F 5 17.38, P 5 , 0.05. Letters signify the plantation ages2,88 2,88

significantly different according to Tukey post hoc tests.

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Figure 4. Plots of PC 1 and the abundance of tracks from four large mammal trophic feeding groups fromthe Kilombero Valley, Tanzania. Teak age: 1993/1994 (d), 1996/1997 (m) and 1998/1999 (s).Trophic groups (a) Grazers (Spearman rank correlation coefficient r 5 20.25, P , 0.05); (b) gleanerss

(r 5 0.45, P , 0.01); (c) bulk feeder (r 5 20.28, P , 0.05), and (d) rooters (r 5 20.23, P , 0.05).s s s

not significantly different between teak age groups, but older plantations were theleast used (Figure 5d).

Track abundance was significantly different depending on the proximity to theflood plain (Table 3). Tracks from gleaners were significantly more abundant inplantations furthest from the flood plain, but tracks from all other trophic groupswere more abundant near to the flood plain (Table 3). Habitat use of teak plantationsmay therefore be influenced by their proximity to other important habitats.

Discussion

The management of wildlife populations outside protected areas is becoming aconservation priority in Tanzania (Newmark 1993). The demand for land by bothpeople and wildlife is increasing the pressure on large mammal populations inparticular (Caro 1999).When land use change occurs, environmental prudence oftendirects conservationists to investigate the effect of such disturbance, with thelonger-term aim of mitigating any negative impacts. Our study therefore contributes

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Figure 5. Mean abundance (1 se) of track scores in three different ages of teak plantation from theKilombero Valley, Tanzania for (a) bushbuck F 5 11.49, P , 0.01; (b) bush pig F 5 3.00, n.s.; (c)2,88 2,88

duiker F 5 9.70, P , 0.01; (d) waterbuck F 5 2.32, n.s.; (e) buffalo F 5 9.07, P , 0.01; (f)2,88 2,88 2,88

warthog F 5 14.10, P , 0.01. Letters signify the plantation ages significantly different according to2,88

Tukey post hoc tests.

to the debate on the conservation of poorly protected areas, habitat fragmentationand the environmentally responsible management of forestry plantations.

Comments on methodology

There is often a need to use cost effective and non-intrusive methods to monitor

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Table 3. Comparisons of mean track abundance for four trophic groups of herbivores from teakplantations at different proximity to the edge of the Kilombero River flood plain. Near (6.8 km from theedge), mid (8.8–10.3 km) and far (11.7 km).

Trophic group F Mean (6se) track abundance2,81

Near Mid Farabc abc abcGrazers 10.2** 2.85 6 0.50 1.30 6 0.25 0.48 6 0.19de d eBulk feeders 19.6** 3.85 6 0.29 1.24 6 0.22 0.80 6 0.29f g fgGleaners 18.6** 0.92 6 0.35 0.63 6 0.13 2.72 6 0.42

h hRooters 6.08* 1.31 6 0.40 1.83 6 0.19 0.80 6 0.15

Letters signify the plantation ages significantly different according to Tukey post hoc tests. **P , 0.01;*P, 0.05.

secretive or endangered mammals (e.g. Kendall et al. (1992) and references therein).Traditional methods used to determine population density from animal signs requiredetailed information on decay and defecation rates (e.g. Plumptre 2000). However,the use of animal signs to indicate relative levels of habitat use does not require suchdetailed information (e.g. Nummelin 1993), but often necessitates a conservativeinterpretation because of the confounding influence of habitat and deposition-decayrates on the detectability of signs. Teak leaves are round, large (approx. length fromolder plantations in the study site 5 0.35–0.55 m) and brittle and the soft groundconditions during April ensured that even the smallest animals (e.g. duiker)punctured the teak leaves when walking over leaf litter. The holes and indentationsproduced in the leaves were characteristic and observers were able to lift the leavesto identify the tracks underneath. We therefore believe that it is unlikely that leaflitter significantly affected the detectability of signs during the study.

Habitat use

Food availability and cover from predators are thought to be the two main pressuresthat effect the distribution and abundance of herbivores (e.g. Mduma and Sinclair1994; Tutin et al. 1997). Our study found significant differences in the abundanceand species composition of a large mammal community in teak plantations ofdifferent ages. We hypothesise that these differences are because of the structuralvariation in the plantations caused by the management cycle of the teak. Thecomposition of the regenerating indigenous vegetation differed only slightly withplantation age (K. Roettcher, unpublished data). However, leaf litter depth, leaf littermass, size of teak trees and the percentage cover of tall vegetation all increased withplantation age. The youngest plantations were characterised by a higher percentagecover of short grass vegetation. Within the area converted to teak, the variation invegetation structure between plantations therefore produced a habitat mosaicconsisting of teak patches of different ages and patches of the remaining originalflora.

We found a distinct assemblage of large mammals using the oldest teak planta-tions that consisted of duiker, bush pig and bushbuck. These three taxa wererecorded at least twice as often from the older plantations compared to the moreopen, younger plantations and are consistent with the results of Hinde et al. (2001a).

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The low use of the younger plantations by bush pig is consistent with theirpreference for denser, semi-evergreen forest (Ghiglieri et al. 1982). Bush pig oftenfeed in small groups and forage for terrestrial insects in leaf litter and rotten wood oreat fallen fruits (Ghiglieri et al. 1982). Duikers are frugivorous but also browse onyoung shrub leaves (Tutin et al. 1997), whilst bushbuck favour shrubs, leguminousherbs and growing grass (Kingdon 1997). Both species favour patches of denseundergrowth which provide cover from predators and a suitable food supply (Okiria1980; Nummelin 1993; Macleod et al. 1996); conditions that were only found in theolder teak plantations.

Warthog, buffalo and waterbuck used the two younger age teak plantations themost, but were also occasionally recorded from the oldest plantations. For warthog,this is likely to be a reflection of specialisation for open, savanna habitats (Estes1991). Ferrar and Walker (1974) and Hirst (1975) reported warthogs to prefer areaswith short grass and high habitat heterogeneity, whilst Rogers (1984) found warthogto avoid thickets, dense woodland and unburnt tall grass communities. Waterbuckare miombo woodland specialists and require open areas of good visibility withextensive lawns of short or medium length grass close to a permanent water source(Kingdon 1982). Waterbuck and other antelope rely on visual stimuli and requireearly detection of danger followed by fast escape to avoid predators (Kingdon 1982;Estes 1991). Teak plantations in the KilomberoValley are relatively small (2–50 ha)and are surrounded by narrow miombo strips, roads and firebreaks; open-woodlandspecies therefore have suitable habitat surrounding the denser teak plantations.

Implications for conservation

Miombo woodland in the Kilombero Valley is an important source of naturalproducts for local people, providing construction materials, fuel, medicine and food(e.g. honey). Consequently, woodlands that are situated close to villages or roads areheavily exploited, and new areas continue to be lost to the expansion of small farms.Teak plantations are therefore not the only threat to the miombo woodland and wehave described the use of farm habitats by antelopes in the Kilombero Valleyelsewhere (Jenkins et al. 2002). However, the teak plantations in this study couldhave significant and long-term impacts locally. The conversion of natural miombowoodland into teak plantations may adversely effect wildlife populations through aloss of habitat in sensitive areas, such as close to the flood plain, or throughfragmentation of the remaining natural habitats.

Studies in India have reported that conversion of natural forests into teakplantations does not affect species richness of small mammals or ungulates, butoverall densities are usually reduced (Karanth and Sunquist 1992; Chandrasekar-raoand Sunquist 1996). Some species, however, such as the chital antelope Axis axis,were more abundant in teak than in other habitats (Karanth and Sunquist 1992). Thecurrent study has shown that teak plantations are widely used by wildlife, with theyounger plantations maintaining a community similar to open woodland and alimited representation of a closed forest community in the older plantations. The

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gradient in habitat structure among teak plantations of different ages thereforeprovides vegetation heterogeneity and patches suitable for different species.

For the true impact of any plantations to be assessed, both connectivity and thetype of adjacent habitat must be taken into account. For example, Zanne et al.(2001) found that levels of habitat use of duiker, bushbuck and bush pig inabandoned softwood pine plantations in Uganda were comparable with adjacentnatural forest. However, the abundance of large mammals was lower in isolatedplantations compared to those surrounded by natural forest. Teak plantations that aresurrounded by miombo woodland and that allow these patches of natural vegetationto be linked are therefore more likely to retain the conservation integrity of an area.Based on the mosaic of suitable habitat patches available for different species in theKilombero Valley, it is likely that the current design consisting of small plantationsplanted in successive years is more beneficial to wildlife than a large block of teakplanted during the same year. Furthermore, by leaving narrow strips or patches ofmiombo woodland surrounding the plantations there is the potential for these areasto serve as wildlife corridors or refuges, although more research is now required toassess the use of these areas.

In the KilomberoValley, plantations that are adjacent to the boundary between theflood plain and miombo woodland are likely to be the most damaging. Althoughnew teak plantations located near the flood plain edge will be used by wildlife in theearly years, our results show that these areas will eventually become unsuitable forspecies such as warthog, buffalo and zebra. It is therefore important to monitorchanges in vegetation structure and the concomitant wildlife use over the 30–40year plantation life span to record the response of wildlife to the changing structureof the teak blocks.

For the impact of fragmentation of the miombo woodland in the KilomberoValley, caused by converting some areas into teak plantations to be limited, theremaining patches of natural woodland require sound management and protection.Farmers, livestock, illegal hunters and wildlife already heavily use the land at theinterface of the flood plain and miombo woodland foothills during the wet season(Jenkins et al. 2003) and further teak planting in this zone should be discouraged.Teak blocks consisting of small plantations of varying age, interspersed with largertracts of miombo woodland situated at least 10 km from the flood plain periphery,probably represent the least damaging protocol for wildlife populations. The loss ofmiombo woodland to teak is probably not the major threat to this habitat type in theKilombero Valley and the presence of large areas of miombo woodland withinKVTC’s boundary, that is unsuitable for teak, provides a real opportunity to managethe remaining woodland for both people and wildlife.

Acknowledgements

This study is a component of the Frontier-Tanzania Savanna Research Programme,funded by the Society for Environmental Exploration (SEE), KilomberoValley TeakCompany (KVTC) and Community Fund, UK. Frontier-Tanzania is a collaboration

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between the University of Dar es Salaam (UDSM) and the SEE and operates inconjunction with Ulanga and Kilombero District Councils and Wildlife Division,United Republic of Tanzania. Particular thanks to Chris Bekker and Crispin Golding(KVTC), Octavian Ngwamba (Catchment Forestry Project), Edward Mlaponi,Salum Musa, Jacob Ndimbo, Israel Manselli and Peter Msumgano (game guards),K.M. Howell and M. Muruke (UDSM) and Eibleis Fanning (SEE) and ResearchAssistants (Frontier-Tanzania).

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