Dipterocarp Rainforest Research Articles

Species richness in an insectivorous bat assemblage from Malaysia

Estimates of insectivorous bat diversity in the Palaeotropics have largely been hampered by the lack of long-term studies employing appropriate capture techniques. Using a variety of trapping methods, 45 insectivorous bat species were captured in approximately 3 km2 of primary dipterocarp rain forest in Malaysia over 8 y. The cumulative site list for Kuala Lompat Research Station, Krau Wildlife Reserve, now stands at 51 insectivorous species. Although this is likely still not a complete list, it is already one of the most species-rich in the world. We attribute much of our success in recording this diversity to the extensive use of harp traps. Of the 45 species, 38 were captured in an intensive harp-trapping programme (> 1030 harp-trap nights) of the forest interior (22 species exclusively so). Insectivorous bats of the forest interior are thus a key component of Old World bat diversity, particularly in South-East Asia, and are dominated by taxa capable of detecting and capturing prey in cluttered environments (Hipposideridae, Rhinolophidae, Kerivoulinae and Murininae).

Drought avoidance and the effect of local topography on trees in the understorey of Bornean lowland rain forest

The water relations of two tree species in the Euphorbiaceae werecompared to test in part a hypothesis that the forest understorey plays anintegral role in drought response. At Danum, Sabah, the relatively commonspecies Dimorphocalyx muricatus is associated with ridgeswhilst another species, Mallotus wrayi, occurs widely bothon ridges and lower slopes. Sets of subplots within two 4 -hapermanent plots in this lowland dipterocarp rain forest, were positioned onridges and lower slopes. Soil water potentials were recorded in1995–1997,and leaf water potentials were measured on six occasions. Soil water potentialson the ridges (−0.047 MPa) were significantly lower than onthe lower slopes (−0.012 MPa), but during the driest periodin May 1997 they fell to similarly low levels on both sites (−0.53MPa). A weighted 40-day accumulated rainfall index was developedtomodel the soil water potentials. At dry times, D.muricatus(ridge) had significantly higher pre-dawn (−0.21 v.−0.57 MPa) and mid-day (−0.59 v.−1.77 MPa) leaf water potentials than M.wrayi (mean of ridge and lower slope). Leaf osmotic potentials ofM. wrayi on the ridges were lower (−1.63MPa) than on lower slopes (−1.09 MPa), withthose for D. muricatus being intermediate (−1.29MPa): both species adjusted osmotically between wet and dry times.D. muricatus trees were more deeply rooted thanM. wrayi trees (97 v. 70cm). M. wrayi trees had greaterlateral root cross-sectional areas than D. muricatus treesalthough a greater proportion of this sectional area for D.muricatus was further down the soil profile. D.muricatus appeared to maintain relatively high water potentialsduring dry periods because of its access to deeper water supplies and thus itlargely avoided drought effects, but M. wrayi seemed to bemore affected yet tolerant of drought and was more plastic in its response. Theinteraction between water availability and topography determines these species'distributions and provides insights into how rain forests can withstandoccasional strong droughts.

Ranging behaviour and activity of the Malay civet (Viverra tangalunga) in a logged and an unlogged forest in Danum Valley, East Malaysia

AbstractThe Malay civet Viverra tangalunga is a relatively little known member of Borneo's carnivore community found throughout Peninsular Malaysia, Palawan, Sumatra and adjacent islands and Sulawesi. To investigate the basic ecology of this species and examine the potential impact of selective logging, a radiotelemetry study was carried out in the Ulu Segama Forest Reserve in Sabah, East Malaysia. From December 1995 to June 1997, home range, movement and activity data were collected on 12 study animals in a dipterocarp rain forest, and comparisons made between civets in a selectively logged and an unlogged site. Mean home‐range size was 110 ha and did not differ between sites or gender. In areas of range overlap, radio‐collared civets tended to avoid one another. Day beds were located on the ground and were associated with dense cover. Activity levels averaged 55% and were similar between forest types and gender. Most activity occurred from 18:00 to 07:00 during which mean activity was 81%. In a single day, males travelled further and covered a larger part of their home range than females. Roads and trails were used by both sexes, and roads were the only observed source of mortality resulting from vehicles. While density was higher in the unlogged forest, this species persists in both areas. The ability to survive in disturbed habitats might be influenced by the proximity of undisturbed habitat that served as a biological reservoir, or source of individuals to immigrate into the disturbed habitat.

Hyper‐abundance of Native Wild Pigs (Sus scrofa) in a Lowland Dipterocarp Rain Forest of Peninsular Malaysia1

ABSTRACTThis study reports extraordinarily high density estimates for the wild pig (Sus scrofa) from an aseasonal tropical forest site within the species'native range. At Pasoh Forest Reserve, a 2500 ha area of lowland dipterocarp rain forest in Peninsular Malaysia, line transects were used to estimate pig density from May to October in 1996 and 1998. In 1996, 44 sightings of S. scrofa consisting of 166 individuals were recorded along 81 km of transects. In 1998, 39 sightings documented 129 individuals along 79.9 km of transects. Estimated population density was 47.0 pigs/km2 in 1996 and 27.0 pigs/km2‐ in 1998. Sus scrofa biomass in this forest was estimated at 1837 kg/km2 and 1346 kg/ km2 in 1996 and 1998, respectively. Differences between years were attributed to changes in the density of young pigs, coincident with a mast‐seeding year of dipterocarp trees in 1996. Pig densities at Pasoh Forest Reserve were much higher than at other forest locations within the species' native range in Europe and Asia. Because Pasoh Forest Reserve is a forest fragment, two factors likely account for the extremely high pig densities: (1) local extinction of natural predators (mainly tigers and leopards) and (2) an abundant year‐round food supply of African oil palm fruits from extensive plantations bordering the reserve.

The Ecological Consequences of Logging in the Burned Forests of East Kalimantan, Indonesia

Results of a 2-year study on post-fire vegetation dynamics in the unlogged dipterocarp rainforest of Sungai Wain near Balikpapan East Kalimantan, Indonesia are discussed. Results showed that the maintenance of a productive permanent forest estate is likely to be served best by avoiding logging activities in burned areas.

Local wind damage in Barito Ulu, Central Kalimantan: a rare but essential event in a lowland dipterocarp forest?

The importance of disturbances for the dynamics of tropical forests has been described by Whitmore & Burslem (1998). Among the phenomena which they classify as large scale disturbances are those caused by wind. The most extensive of these occur within the hurricane (cyclone) belt (10-20° from the equator) but outside this belt large blowdowns of trees are known to occur, perhaps most spectacularly in the Brazilian Amazon (Nelson et al. 1994). There is evidence that rare wind storms influence the dipterocarp rain forests of Peninsular Malaysia, 2-6°N. One famous storm in November 1880 which devastated hundreds of square kilometres of forests in Kelantan, north-east Malaya, was probably an aberrant cyclone (Wyatt-Smith 1954). Smaller windstorms which have blown down several hectares of forests have been reported from Malaysia including Borneo (Ashton 1993) but their frequency and extent have not been well documented (Whitmore & Burslem 1998). At Barito Ulu, Central Kalimantan, one such storm occurred recently and the fortuitous combination of a well patrolled trail system and the localization of the storm has allowed a detailed assessment of the forest damage.

Hyper-abundance of Native Wild Pigs (Sus scrofa) in a Lowland Dipterocarp Rain Forest of Peninsular Malaysia1

Abstract This study reports extraordinarily high density estimates for the wild pig (Sus scrofa) from an aseasonal tropical forest site within the species' native range. At Pasoh Forest Reserve, a 2500 ha area of lowland dipterocarp rain forest in Peninsular Malaysia, line transects were used to estimate pig density from May to October in 1996 and 1998. In 1996, 44 sightings of S. scrofa consisting of 166 individuals were recorded along 81 km of transects. In 1998, 39 sightings documented 129 individuals along 79.9 km of transects. Estimated population density was 47.0 pigs/km2 in 1996 and 27.0 pigs/km2 in 1998. Sus scrofa biomass in this forest was estimated at 1837 kg/km2 and 1346 kg/km2 in 1996 and 1998, respectively. Differences between years were attributed to changes in the density of young pigs, coincident with a mast-seeding year of dipterocarp trees in 1996. Pig densities at Pasoh Forest Reserve were much higher than at other forest locations within the species' native range in Europe and Asia. B...

Simulation of the growth of a lowland Dipterocarp rain forest with FORMIX3

In this paper a new model for simulation of the growth of tropical rain forest is presented (FORMIX3). The model describes growth, mortality, recruitment of trees and competition between trees. The calculation of tree growth is based on a carbon balance. The carbon gain of a tree depends on the photo production of its leaves, respiration and other losses. Trees compete for light and space. Dying large trees fall down and create gaps in the forest. Based on an extensive field data review, a parametrisation was developed for the simulation of lowland Dipterocarp rain forest at Deramakot, Malaysia. A total of 28 variables describing different aspects of forest structure and growth were compared with field data. The model reproduces most parts of the forest dynamics well. A new concept for sensitivity analysis is presented: 46 model parameter were varied and analysed in respect to their influence on 26 variables describing the forest state. The influence of the different processes on forest structure is complex. Some general trends can be observed: The growth characteristics of the two Dipterocarp species groups strongly influences species composition in the forest, but not general forest structure (biomass, leaf area, production, leaf area, tree size distribution)

Concepts for the aggregation of tropical tree species into functional types and the application to Sabah's lowland rain forests

For analysing field data as well as for modelling purposes it is useful to classify tree species into a few functional types. In this paper a new aggregation of tree species of the dipterocarp rain forests in Sabah (Borneo), Malaysia, is developed. The aggregation is based on the two criteria successional status and potential maximum height. Three classes of successional status (early, mid and late successional species) and five classes of potential maximum heights (≥ 5 m, 5–15, 15–25, 25–36, > 36 m) lead to a combination of 15 functional types. The criteria of the developed classification are chosen to suit for applications with process-based models, such as FORMIX3 and FORMIND, which are based on photosynthesis production as the main process determining tree growth. The concept is universal and can easily be applied to other areas. With this new method of grouping a more realistic parametrization of process-based rain forest growth models seems to be possible.

Habitat associations of trees and seedlings in a Bornean rain forest

Summary 1 In species‐rich mixed dipterocarp rain forest in Indonesian Borneo, we evaluated evidence for tree species associations with physical habitat variables (physiography for adults and seedlings, and light for seedlings). A total of 325 species were included in the analysis. 2 A stratified random sample of 28 tree and seedling plots (0.16 ha and 36 m2, respectively) was taken from a 150‐ha study area on homogeneous parent rock (granite) between 110 and 270 m a.s.l. 3 In a principal component analysis (PCA), based on an abundance index of all tree species, plots segregated into three groups. These corresponded closely with the three physiographically defined habitat types assigned in the field: (i) plateaux with a deep humus layer, (ii) sharp ridges and upper slopes, and (iii) gullies and lower slopes near permanent streams. Segregation of plots by habitat was weaker when seedling (rather than tree) species abundance was used in the PCA. 4 In single species analyses, using Monte Carlo randomization tests, we found significant associations with the three physiographic habitat types in 17 out of 49 abundant species for trees, and in 5 out of 22 abundant species for seedlings. In PCA and single species analyses, weaker associations with habitat for seedlings than for trees suggest higher mortality of seedlings in ‘suboptimal’ habitats. 5 Seedlings of 8 out of 45 abundant species were also significantly and positively associated with high light availability (measured in 2 × 2 m subplots, using hemispherical photographs). 6 Combining light and physiographic habitat associations, 20 out of the 45 abundant species were associated with at least one habitat factor as either adults or seedlings. 7 Thus, the distributions and abundances of many species are influenced by local heterogeneity in physical habitat variables. However, about half of the abundant species (25 of 45) showed no significant habitat association as adults or seedlings, and in no case did the relative abundance of any species exceed 5% in its ‘preferred’ habitat.

Does Reduced-Impact Logging Help Preserve Biodiversity in Tropical Rainforests? A Case Study from Borneo using Dung Beetles (Coleoptera: Scarabaeoidea) as Indicators

The role of reduced-impact logging on the preservation of biodiversity in tropical lowland dipterocarp rainforest is examined by looking at differences in dung beetle community structure between two sites logged in 1993: one harvested using reduced-impact methods and one using conventional techniques. Collections were made using two flight intercept traps over 7 d, and samples were compared with previous collections made from primary forest (riverine and interior-forest) and older forest logged using conventional techniques (logged in 1981). Of the two 1993 sites, the higher diversity and species richness (S = 57, n = 969, alpha = 13.23, H′ = 3.24) was recorded in the forest logged using reduced-impact techniques: the conventionally logged site had both lower diversity and species richness (S = 48, n = 1968, alpha = 8.88, H′ = 1.89), and lacked some primary forest specialists present in the reduced-impact forest samples. The dung beetle community in the 1993 conventional logged site is similar to that of the conventional logging site harvested in 1981. Primary forest has a well-defined ecotone, from interior to riverine forest: both 1993 sites contain a mixture of interior-forest and riverine specialists that are usually spatially separated along this ecotone. Although the dung beetle assemblage in the forest harvested by reduced-impact logging is more similar to a primary interior-forest assemblage than the conventionally logged site, both 1993 sites have assemblages that are closer in similarity to assemblages from primary-riverine habitat than they are to ones from primary interior-forest. However, because the forest logged using reduced-impact logging techniques has a more equitable and diverse dung beetle assemblage and a greater number of interior-forest specialists than the conventionally logged site, this study suggests that reduced-impact logging has better preserved the primary forest assemblage than conventional logging techniques.

Distance-dependence in herbivory and foliar condition for juvenile Shorea trees in Bornean dipterocarp rain forest.

We assessed density- and distance-dependence in herbivore effects and juvenile condition for four species of Shorea, the most speciose genus in the dominant canopy family of southeast Asian rain forest trees (Dipterocarpaceae). Herbivore damage was quantified as partial leaf loss on young leaves, and whole plant foliar condition as the product of the fraction of leaf nodes containing leaves and the fraction of tissue remaining on extant leaves. Adults of the four species were centers of high total, as well as conspecific, density of juveniles (<1 m tall). For two species, S. hopeifolia and S. pinanga, herbivore damage declined significantly with distance, decreasing by 40% and 51% respectively, between 5 m and 35 m from the parent. For the same two species, foliar condition improved significantly between 5 m and 35 m, increasing by 45% for S. hopeifolia and 24% for S. pinanga. If foliar condition influences juvenile survival and growth, more widely dispersed seeds of these species are more likely to recruit to the canopy. In contrast, there was no significant distance-dependence for S. parvifolia or S. longisperma. Among species, herbivore damage was greatest in those species with greatest local juvenile abundances, i.e., those with highest densities, leaf size, juvenile foliar mass and/ or foliar mass/m2 ground area, but was unrelated to the toughness of mature leaves. However, distance was a better predictor of herbivore damage than was conspecific juvenile density, as evaluated by backward elimination regressions, for both S. hopeifolia and S. pinanga. For foliar condition, the best predictor was distance for S. pinanga, but conspecific density for S. hopeifolia, whose juveniles were smallest and occurred at the highest densities. Total juvenile density (all woody plants) was eliminated as a factor in all cases. The species-specificity of effects (i.e., their dependence on conspecific distance or density), together with the marked differences among congeneric species, caution against generalizations regarding distance-dependent effects in diverse forests.

Spatial heterogeneity of element and litter turnover in a Bornean rain forest

ABSTRACT. The spatial heterogeneity of element fluxes was quantified by measuring litterfall, throughfall and litter decomposition for 1 y in 30 randomly located sampling areas in a lowland dipterocarp rain forest. The idea tested was that turnover of elements is more variable than turnover of dry matter in a forest with extremely high tree species diversity. In spite of the low fertility of the soil (an ultisol), total litter production (leaves, trash, and wood &lt;2 cm in diameter) was high (1105 g m−2 y−1) with inputs to the forest floor of carbon, nitrogen, phosphorus, calcium, magnesium, potassium, manganese and iron of 550, 15.3, 0.47, 6.26, 2.49, 4.75, 0.95 and 0.14 g m−2 y−1 respectively. Throughfall was 81% of the annual rainfall and transferred 22.2, 1.37, 0.14, 1.07, 0.67, 0.39, 7.92, &lt;0.06, and &lt;0.06 g m−2 y−1 of organic carbon, nitrogen (all forms), phosphorus, sulphur, calcium, magnesium, potassium, manganese and iron, respectively. Average turnover rates of nutrients in litter were highest for potassium and decreased in the sequence calcium, magnesium, carbon, nitrogen and phosphorus. Concentrations of phosphorus, nitrogen and potassium in litterfall, litter mass and topsoil were closely correlated with each other. Concentrations of calcium and manganese were positively correlated with each other and with elevation. Variations in leaf chemistry and total litterfall caused the spatial heterogeneity of element input to the forest floor to have a coefficient of variation of 30 — 70%, depending on the element. Due to the strong positive correlation between element fluxes and pools, the spatial variability of turnover rates (CV c. 20%) was lower than that of element input. Turnover rates for K varied by a factor of 4, and for Ca by a factor of 2.8 when the different sites were compared. The results strongly suggest that the most important factor determining spatial heterogeneity of organic matter and element dynamics on the forest floor is the site-specific amount of leaf fall, rather than spatially variable decomposition rates.

The effects of tree species grouping in tropical rainforest modelling: Simulations with the individual-based model F ormind

Due to high biodiversity in tropical rainforests, tree species are aggregated into functional groups for modelling purposes. In this article the influences of two different classifications of tropical tree species into functional groups on the output of a rainforest model are analysed. The F ormind model is documented. F ormind simulates the tree growth of tropical rainforests. The model is individual-based and developed from the F ormix3 model. In the model, trees compete for light and space in plots of 20×20 m in size. A carbon balance is calculated based on the processes of photosynthesis and respiration. Using a tree geometry submodel, typical tree variables (e.g. diameter, height, crown length) are calculated. The mortality process is mainly driven by falling trees and the canopy gaps they create. Trees of the same functional group and diameter class are represented in one cohort. Simulation results for a primary lowland dipterocarp rainforest in Sabah, Malaysia, are discussed. Detailed structural characteristics of the rainforest stands can be analysed, e.g. the simulation results support the hypothesis that rainforests grow in a layer structure. A comparison of results for the aggregation of 436 tree species into five or 22 functional groups respectively, shows that typical results, such as total stem volume or crown closure, achieved with five groups are as accurate as simulations with a huge number of groups. However, some features such as interspecific competition can only be analysed with a huge number (e.g. 22) of functional groups. The model has the potential to analyse extinction processes and spatial structure of gap formations in rainforests. The analysis of logging scenarios could estimate the effects of human impacts in tropical rainforests.

Photosynthesis rates of selected tree species in lowland dipterocarp rainforest of Sabah, Malaysia

Diurnal courses of net photosynthesis, transpiration and water potential of leaves of ten woody species from the natural lowland dipterocarp forests in Sabah (North Borneo, Malaysia) and one exotic tree species were studied in the field. The indigenous species represent different ecological niches and successional stages in the various layers of the dipterocarp forest, such as pioneers, trees of the understorey or main canopy and emergents. Diurnal changes in CO2 exchange and transpiration reflected primarily differences in irradiance. The diurnal courses of water potential mainly tracked the rate of transpiratory water loss. Light-dependency describes most of the diurnal variations of leaves’ gas exchange. Light response curves of net photosynthesis of the investigated species of the Dipterocapaceae were almost equal (light saturated assimilation rate, Amax: 5.0–7.2 μmol CO2 m–2 s–1), while those of the other species exhibited remarkable differences (Amax: 5.5–14.2 μmol CO2 m–2 s–1). Leaf area, chlorophyll content and specific leaf dry weight as the reference parameters for assimilation gave a general ranking of the Amax, which is highest for the pioneering species, less for the understorey trees and lowest for emergents. Light compensation points and light saturation of net photosynthesis were attained mainly between 6 and 9 μmol photons m–2 s–1 and between 230 and 534 μmol photons m–2 s–1, respectively, but were higher for pioneering species. Photosynthetic performance may be a diagnostic feature of the successional and ecological status of species, i.e. to characterize pioneering species from understorey species or from emergents of the dipterocarp forest.

Photosynthetic Induction and Stomatal Oscillations in Relation to the Light Environment of Two Dipterocarp Rain Forest Tree Species

1 This paper reports on changes in photosynthetic induction and stomatal conductance (g,) in response to (i) continuous saturating light and (ii) darkness, for seedlings of two climax tree species (Shorea leprosula and Dryobalanops lanceolata, Dipterocarpaceae) growing in three differing rain forest light environments (ranging from 2 4 to 21 8 mol photon m-2 day-') in Malaysian Borneo. 2 For some species in understorey environments, a high proportion of diurnal carbon gain is attained during sunflecks (transient periods of high light), and D. lanceolata is slower growing than S. leprosula but its seedlings can survive under deeper shade conditions. Our aim was to determine whether interspecific differences in dynamic photosynthetic responses to light could further explain observed differences in seedling ecology. 3 In contrast to the expected trend for shade-tolerant species, D. lanceolata showed faster induction in higher light environments and S. leprosula showed no relationship between light environment and induction rate. However, both species showed greater potential sunfleck utilization efficiency in low light environments through slower rates of both induction loss and stomatal closure. 4 Shorea leprosula attained greater rates of maximal photosynthesis and gs, had faster rates of induction and retained a higher level of induction in prolonged darkness (> 30 min) than D. lanceolata in all light environments. However, S. keprosula showed faster induction loss and stomatal closure in the short term (10 min) than D. lanceolata, which, together with a potentially negative carbon balance between sunflecks, may limit its distribution to microsites of higher sunfleck frequency. 5 The balance between photosynthesis (A) and gs during induction resulted in a constant intercellular CO2 concentration of c. 270 p.p.m. after c. 11 min, which may represent a physiological optimum for both species. 6 In some circumstances transient peaks in A and ga were observed during induction, rather than a rise to a stable maximum, which we attribute to overcompensation of the stomatal response to light. In some cases for S. leprosula this initiated synchronized damped oscillations in gs and A that continued for c. 1 h in both continuous and discontinuous (80-s light/80-s dark) light. 7 Shorea leprosula plants with the ability to 'peak' or oscillate had the potential to increase both the rate and magnitude of response to sunflecks in comparison with simple sigmoidal induction.

The geometry of the canopy of a dipterocarp rain forest in Sumatra

A study was conducted in a lowland dipterocarp rain forest in Sumatra to assess the structure and dynamics of the forest canopy. The canopy structure was analysed at different scales, including a previous mapping of a 5 ha forest mosaic and an interpretation of the canopy architecture, along a horizontal gradient between the high forest and a 320 m2 treefall. Canopy geometry was ascertained by analysis of digitized zenithal hemispherical photographs sampled at 25 near-ground sites. Gap size, morphology and dispersion varied continuously from the high forest to the treefall. An asymmetric pattern of gaps about the zenith was characteristic of almost all forest sites. The spatial dispersion of gaps was random in the high forest. It tended to be dumped in the forest border and in the treefall. Plant area indices ranged from 6.5 in the high forest to 2.9 in the treefall. These values reflect a reduced leaf area during a severe dry spell, at the time of measurements. Inclination angles of canopy elements were highly correlated with gap dispersion and canopy openness, as observed from the high forest to the treefall. Implications of canopy heterogeneity on the distribution of light were analysed. The importance of lateral light penetrating from the forest border into the high forest is stressed. The canopy gradient of architecture and geometry from the high forest to the treefall and the very diverse structure of the high forest are emphasized.

Effect of gap liberation on the performance and growth of dipterocarp trees in a logged-over rainforest

Large parts of southeast Asian dipterocarp rainforests have been overlogged by applying different systems of selective cutting. Logged-over forests are expected to re-establish the original dipterocarp stock through natural regeneration. Post-logging silvicultural operations, notably crown liberation and enrichment planting, are conducted to ensure sustained yield. These techniques have largely failed to achieve the desired goal. We tested the effect of gap liberation on the performance and growth of dipterocarp trees in an overlogged concession area in south Kalimantan, Indonesia. Twelve gaps, 500–1600 m 2 in size, were sampled based on the occurrence of ephemeral dipterocarp seedling stock (notably Shorea spp.) under the canopy. Six gaps were opened up 6 years after the logging and inventoried, together with the untreated gaps, 12 years after the logging. In liberated gaps, dipterocarps accounted for 77% of the total basal area, compared with 20% in the untreated area. Survival of dipterocarps was 33% higher and diameter twice as high in liberated gaps as in the untreated plots. In height, no significant difference was detected. Liberation also improved the quality of dipterocarp trees in terms of stem and crown form. The volume of red meranti ( Shorea spp.) in liberated gaps was 90 m 3 compared with 36 m 3 in the untreated area. Gap liberation was proved as a silviculturally and economically feasible management alternative of overlogged dipterocarp rainforests.

The Influence of Logging on a Malaysian Dipterocarp Rain Forest: a Study Using a Forest Gap Model

We present the first application of a forest gap model to the study of logging techniques in Malaysian tropical Dipterocarp rain forests. The aim of this paper is to reveal the impact of different logging techniques on forest composition, sustainability and logged biomass. We performed simulations both with and without damage to trees due to harvesting. The latter simulations allowed us to deduce that an optimum logging cycle of 100 years maximizes yield. In contrast, short logging cycles of 20 years show low yields and dramatic changes in the species composition of the forest. To restore the species composition to its undisturbed state, a regeneration time of 200 years is needed. From our simulations we deduce that it is crucial to take logging damage into account in order to obtain realistic descriptions of both the yield and forest composition.

Differences in light energy utilisation and dissipation between dipterocarp rain forest tree seedlings.

The light environment within tropical rain forests varies considerably both spatially and temporally, and photon flux density (PFD) is considered to be an important factor determining the growth and survival of rain forest tree seedlings. In this paper we examine the ability of four ecologically contrasting dipterocarps (Dryobalanops lanceolata, Shorea leprosula, Hopea nervosa and Vatica oblongifolia) to utilise and dissipate light energy when grown in different light environments in lowland dipterocarp rain forest in the Danum Valley Conservation Area, Sabah, East Malaysia. Specifically we report (i) photosynthetic light response curves and associated fluorescence characteristics, including quantum yield (ΦPSII) and non-photochemical quenching (qN) and (ii) the extent to which photoinhibition occurs when plants grown in either high or low light are exposed to short bursts of high PFD. When grown in low light (artificial or forest shade) all four species had low light saturated rates of photosynthesis which were achieved at low PFDs. In addition, values of ΦPSII and qN were similar over a range of measurement PFDs. D. lanceolata and S. leprosula were also grown at high PFD and showed marked differences in their responses. S. leprosula demonstrated an ability to increase its rate of photosynthesis and there was a small increase in capacity to dissipate excess light energy non-photochemically at high PFDs. Partitioning of this qN into its fast, photo-protective (qE) and slow, photoinhibitory (qI) components indicated that there was an increase in qE quenching. In contrast, although D. lanceolata survived in the high light environment, greater rates of photosynthesis were not observed and the plants showed a greater capacity to dissipate energy non-photochemically. Partitioning of qN revealed that the majority of this increase was attributable to the slower relaxing phases.