Tropical Rain Forests Of Southeast Asia Research Articles

English

Although, soil properties of tropical rainforest in Southeast Asia have been characterized by several researchers, limited information exists on soil characteristics due to conversion of natural forest into various land use types such as oil palm plantation, rubber plantation, forest plantation and secondary forest. A study was conducted to characterize the soil properties under various land use types of logged-over forest (LF), rehabilitation forest (RF), oil palm (OP) and rubber plantation (RP) at Universiti Putra Malaysia, Bintulu, Sarawak, Malaysia. Soil profiles were dug up to 100 cm depth and 50 cm width and were followed by soil sampling according to soil horizon. Soil morphology was determined in the field while soil physico-chemical properties were determined in the laboratory using standard soil analysis. The soils at RF, LF, OP and RP were derived from sandstone intercalated with shale which gives silty loam and sandy clay loam texture. The soils are acidic to weakly acidic with pH increases with depth. The Cation Exchange Capacity (CEC) and Total Carbon (TC) of soils tend to decrease with depth and it seems to be higher under OP and RP as compared to RF and LF. The Alo, Ald, Feo and Fed increased with depth in all of the profiles. The values of Point Zero of Salt Effect (PZSE) and σp are low in all sites with dominated by kaolin minerals and sesquioxide properties indicating that the soils are highly weathered and low soil fertility status.   Key words: Forest rehabilitation, logged-over forest, oil palm and rubber plantation, charge characteristic.

Mapping Distribution of Dipterocarpus in East Kalimantan, Indonesia

Dipterocarps (Dipterocarpaceae) is a dominant tree family of tropical rainforest in Southeast Asia. Dipterocarps have been exploited for its timber and disappearing fast in East Kalimantan. In this study, we predicted the distribution of dipterocarpus, one of the main dipterocarps genera, by evaluating its habitat suitability using logistic regression analysis with specimen collection points and environmental factors from GIS data. Current distribution of dipterocarpus was generated by combining the habitat suitability classes with an updated forest cover map. Rainfall, soil type, followed by elevation was the main factors that influence the distribution of dipterocarpus in East Kalimantan. Dipterocarpus can be found in a quarter of the current forest cover, which is highly suitable as habitat of Dipterocarpus.

Drought‐induced mortality of a Bornean tropical rain forest amplified by climate change

Drought‐related tree mortality at a regional scale causes drastic shifts in carbon and water cycling in Southeast Asian tropical rain forests, where severe droughts are projected to occur more frequently, especially under El Niño conditions. We examine how the mortality of a Bornean tropical rain forest is altered by projected shifts in rainfall, using field measurements, global climate model (GCM) simulation outputs, and an index developed for drought‐induced tree mortality (Tree Death Indexη) associated with a stochastic ecohydrological model. All model parameters have clear physical meanings and were obtained by field observations. Rainfall statistics as primary model forcing terms are constructed from long‐term rainfall records for the late 20th century, and 14 GCM rainfall projections for the late 21st century. These statistics indicate that there were sporadic severe droughts corresponding with El Niño events, generally occurring in January–March, and that seasonality in rainfall will become more pronounced, e.g., dry (January–March) seasons becoming drier and wet (October–December) seasons becoming wetter. The computedη well reflects high tree mortality under severe drought during the 1997–1998 El Niño event. For the present, model results demonstrate high and low probabilities of mortality in January–March and October–December, respectively, and they predict that the difference in such probabilities will increase in the future. Such high probability of mortality in the dry season is still significantly high, even considering the beneficial effect of increased soil water storage in the wet season (which is projected to increase in the late 21st century).

Erratum to: Comparative chloroplast DNA phylogeography of two tropical pioneer trees, Macaranga gigantea and Macaranga pearsonii (Euphorbiaceae)

Macaranga (Euphorbiaceae) has received much ecological and evolutionary research attention as a genus that includes some of the most conspicuous pioneer trees of Southeast Asian tropical rainforests and because of its manifold associations with ants, including about 30 species that are obligate ant-plants (myrmecophytes). We used sequence data from three chloroplast DNA loci (ccmp5, ccmp6, atpB-rbcL) to assess phylogeographical patterns in species of Macaranga, section Pruinosae, sampled from various regions of Borneo and the Malay Peninsula. Forty-nine chloroplast DNA haplotypes (HT) were identified among 768 specimens from five species, Macaranga gigantea (N = 329; 23 HT), Macaranga pearsonii (N = 347; 21 HT), Macaranga puberula (N = 24; 4 HT), Macaranga hosei (N = 48; 6 HT), and Macaranga pruinosa (N = 20; 5 HT). Forty-one haplotypes were species-specific, whereas eight haplotypes were shared by two, three, or four species and occupied internal positions in a parsimony network. Population genetic parameters based on haplotype frequencies proved to be in a similar range in the non-myrmecophytic M. gigantea and in the ant-associated M. pearsonii, which have overlapping distributions in northern and eastern Borneo. A comparison of GST and NST values revealed a strong phylogeographic structure in both species, whereas colonization pathways suggested by the network topology were different. Both species exhibited similar levels of haplotypic diversity and moderate to high levels of population differentiation. There were no obvious indications for an influence of the symbiotic ant partners on the population structure of their host plants.

The impact of rubber plantations on the diversity and activity of understorey insectivorous bats in southern Thailand

Although a large proportion of tropical rain-forest in South-east Asia has been replaced by rubber plantations, there is very little information about the impact of such forest conversion on bat diversity. To address this deficiency, trapping and acoustic monitoring programmes were carried out in Ton Nga Chang and Khao Ban That wildlife sanctuaries in southern Thailand with the purpose of comparing species diversity and activity of understorey insectivorous bats at sites in forest and in nearby monoculture rubber plantations. Insect biomass in both habitats was assessed. Bat species diversity and activity were found to be much lower in rubber plantations than in forested areas and mean insect biomass was determined to be more than twice as high in the latter habitat than in the former. Bats utilising forest were shown to have significantly higher call frequencies but marginally lower wing loadings and aspect ratios than bats found in both habitats. Management strategies to increase biodiversity in rubber plantations are discussed.

Aerosol fluxes and dynamics within and above a tropical rainforest in South-East Asia

Abstract. Atmospheric aerosol measurements were conducted near Danum Valley, in the Malaysian state of Sabah, North-East Borneo, as part of the OP3 and ACES projects, in April and June/July 2008. Here, aerosol fluxes and diurnal variability in and above the rainforest canopy were examined in order to gain an understanding of their behaviour in the surface layer of the South-East Asian rainforest. Aerosol fluxes were calculated by eddy covariance from measurements above the rainforest canopy on the Global Atmosphere Watch (GAW) tower. Upward fluxes were seen on most mornings between 09:00 and 11:00 local time and this could be attributed to venting of the nocturnal boundary layer as it broke up in the morning. Measurements were also conducted within the canopy and trunk space at a nearby site. Profiles in aerosol number concentrations were investigated using GRIMM Optical Particle Counters (OPCs) at various levels within the rainforest canopy and trunk space, as well as a single OPC on a vertically moving platform. These showed an overnight increase in larger particles (1–20 μm) at all levels, but much more prominently near the top of the canopy, which could be attributed to fog formation. At ground level, number concentrations in this size range correlated with enhancements in biological aerosol concentrations, measured using a Wide Issue Bioaerosol Spectrometer (WIBS) located near the forest floor, suggesting that coarse particle number concentrations were dominated by biological aerosols. A comparison of particle number concentrations (in the size range 0.5–1.0 μm) between above canopy and the trunk space showed correlations, despite turbulence data suggesting persistent decoupling between the two measurement sites. These correlations often relied on a shift of the particle time-series against each other, implying a time delay in observations between the sites, which varied according to time of day. This lag time was shortest during the middle of the day by a significant margin. This was not observed for aerosols larger than 1.0 μm. Further evidence of daytime coupling between above canopy and the trunk space in terms of aerosol measurements is implied by comparison of measurements from an Aerosol Mass Spectrometer (AMS) at the GAW tower and simultaneous bag sampling at the in-canopy site, subsequently analysed with the AMS. Transport of particles through the canopy seems to occur through large-scale, sporadic turbulent events, suggesting that the coupling between the canopy space and the air above is due to these ventilation events.

Traditional land use associated with swidden agriculture changes encounter rates of the top predator, the army ant, in Southeast Asian tropical rain forests

We examined the effect of traditional swidden agriculture on biodiversity using the litter arthropod top predator, the army ant Aenictus (Hymenoptera: Formicidae) as an indicator species in and around an intact tropical rain forest in Sarawak, Borneo, Malaysia. We compared the encounter rates with Aenictus colonies among five forest types: continuous primary forest, isolated primary forest, old secondary forest (>20 years elapsed after abandonment of the fields), young secondary forest (5 years after abandonment), and new fallow (2 years after abandonment) by intensive area searching in 2003 and 2005. In total, seven Aenictus species (15 colonies) and six Aenictus species (11 colonies) were encountered in 2003 and 2005, respectively. The encounter rates were the highest in continuous and isolated primary forests, intermediate in old and young secondary forests, and the lowest in new fallow. Year and the interaction between year and forest type were not significant. That is, abundance of top predators, which is rare and likely to be vulnerable to disturbance, has never fully recovered even 20 years after the termination of cultivation. We discuss forest management strategies to sustain biological diversity.

Phylogenetic systematics of Hoya (Apocynaceae)

Hoya with perhaps 300 species is one of the most diverse angiosperm genera in the tropical rainforests of Southeast Asia and New Guinea. Knowledge of the number of species and their relationships is still very unsatisfactory. Floral characters have been used to subdivide the genus into sections, although none of these groups were based on phylogenetic relationships. Recently, molecular phylogenetic studies have shed new light on the intrageneric relationships of the genus by identifying three main monophyletic clades, in addition to a core Hoya group that includes most of the species examined. One clade includes New Guinean/Australian species, while the other two, the Acanthostemma and the Eriostemma clades, mainly correspond to existing sections. I here discuss the phylogenetic findings in the light of the traditional morphological classifications, as a first step towards a new classification of Hoya based on phylogenetic relationships.

Plant–pollinator interactions in tropical monsoon forests in Southeast Asia

Forests with different flora and vegetation types harbor different assemblages of flower visitors, and plant-pollinator interactions vary among forests. In monsoon-dominated East and Southeast Asia, there is a characteristic gradient in climate along latitude, creating a broad spectrum of forest types with potentially diverse pollinator communities. To detect a geographical pattern of plant-pollinator interactions, we investigated flowering phenology and pollinator assemblages in the least-studied forest type, i.e., tropical monsoon forest, in the Vientiane plain in Laos. Throughout the 5-year study, we observed 171 plant species blooming and detected flower visitors on 145 species. Flowering occurred throughout the year, although the number of flowering plant species peaked at the end of dry season. The dominant canopy trees, including Dipterocarpaceae, bloomed annually, in contrast to the supra-annual general flowering that occurs in Southeast Asian tropical rain forests. Among the 134 native plant species, 68 were pollinated by hymenopterans and others by lepidopterans, beetles, flies, or diverse insects. Among the observed bees, Xylocopa, megachilids, and honeybees mainly contributed to the pollination of canopy trees, whereas long-tongued Amegilla bees pollinated diverse perennials with long corolla tubes. This is the first community-level study of plant-pollinator interactions in an Asian tropical monsoon forest ecosystem.

Population fluctuations of light-attracted chrysomelid beetles in relation to supra-annual environmental changes in a Bornean rainforest

In Southeast Asian tropical rainforests, two events, severe droughts associated with the El Niño-Southern Oscillation and general flowering, a type of community-wide mass flowering, occur at irregular, supra-annual intervals. The relationship between these two supra-annual events and patterns of insect population fluctuations has yet to be clearly elucidated. Leaf beetles (Chrysomelidae) are major herbivores and flower-visitors of canopy trees, affecting their growth and reproduction and, in turn, affected by tree phenology; but their population fluctuations in the Southeast Asian tropics have not been extensively investigated. We examined population fluctuation patterns of the 34 most dominant chrysomelid species in relation to the two supra-annual events by conducting monthly light-trapping over seven years in a lowland dipterocarp forest in Borneo. Our results showed large community variation in population fluctuation patterns and a supra-annual (between-year) variation in abundance for most of the dominant chrysomelids that was significantly larger than the annual (within-year) variation. Specifically, in response to a severe drought in 1998, chrysomelid species exhibited different population responses. These results show that population fluctuations of individual species, rather than the entire assemblage, must be analyzed to determine the effects of changes in environmental conditions on the structure of insect assemblages in the tropics, especially in regions where supra-annual environmental changes are relatively more important than seasonal changes.

Phenology of Tropical Birds in Peninsular Malaysia: Effects of Selective Logging and Food Resources

AbstractThe increasing prevalence of selective logging in Southeast Asian tropical rainforests compels much-needed studies to examine its effects on the vital life-cycle events of their resident understory birds, which are particularly sensitive to such degradation. Food abundance, which can be an important factor in avian phenology, may be affected by selective logging. Therefore, studies that compare food abundance and breeding and molting occurrence simultaneously at the same sites are important for the ecological monitoring of such logging regimes. Using bimonthly mist netting in two rainforest areas in Peninsular Malaysia, we assessed the breeding and molting occurrence and diets of understory birds and compared the abundance of food resources in unlogged forests and forests that had been selectively logged 30 years before. Our study revealed no differences between forest types in overall understory-resident bird abundance; comparative species richness; feeding-guild composition; breeding and molting occurrence and temporal variation; or arthropod, fruit, and flower abundance. The similarity in food resources could account for the similarity in avian phenological characteristics between forest types. Increased breeding corresponded with increased food abundance at the feeding-guild level, and dietary data supported these findings. Breeding cycles of sensitive indicator groups such as understory resident birds are likely to depend on food abundance and forest structure and, thus, on selective logging. Our observation of undiminished avian breeding and molting occurrence in selectively logged forests is an encouraging indication of their conservation potential. However, we emphasize that differences in selective logging practices could affect the forest structure and avifauna differently. Setting thresholds for extraction and regeneration time and subscribing to minimum-impact methods that reduce collateral damage are essential if selectively logged areas are to maintain most of their initial biodiversity.Fenología de Aves Tropicales en Malasia Peninsular: Efectos de la Tala Selectiva y los Recursos Alimenticios

PHENOLOGY OF TROPICAL BIRDS IN PENINSULAR MALAYSIA: EFFECTS OF SELECTIVE LOGGING AND FOOD RESOURCES

Abstract The increasing prevalence of selective logging in Southeast Asian tropical rainforests compels much-needed studies to examine its effects on the vital life-cycle events of their resident understory birds, which are particularly sensitive to such degradation. Food abundance, which can be an important factor in avian phenology, may be affected by selective logging. Therefore, studies that compare food abundance and breeding and molting occurrence simultaneously at the same sites are important for the ecological monitoring of such logging regimes. Using bimonthly mist netting in two rainforest areas in Peninsular Malaysia, we assessed the breeding and molting occurrence and diets of understory birds and compared the abundance of food resources in unlogged forests and forests that had been selectively logged 30 years before. Our study revealed no differences between forest types in overall understory-resident bird abundance; comparative species richness; feeding-guild composition; breeding and moltin...

Modeling CO2 exchange over a Bornean tropical rain forest using measured vertical and horizontal variations in leaf‐level physiological parameters and leaf area densities

Southeast Asian tropical rain forests are among the world's most important biomes in terms of global carbon cycling; nevertheless, the impact of environmental factors on the ecosystem CO2 flux remains poorly understood. One‐dimensional multilayer biosphere‐atmosphere models such as soil‐vegetation‐atmosphere transfer (SVAT) models are promising tools for understanding how interactions between environmental factors and leaf‐level physiological parameters might impact canopy‐level CO2 exchange. To examine application of the SVAT model in tropical rain forests, which is expected to be difficult partly because of the complex canopy structure and large number of tree species, we measured vertical and horizontal variations in leaf‐level physiological parameters and leaf area densities together with eddy covariance measurements using a canopy crane in a tropical rain forest in Sarawak, Malaysia. Despite differences in species and canopy positions, leaf nitrogen per unit area (Na) within the canopy could be one‐dimensionally described as a linear function of height. Na also clearly explained the other leaf‐level physiological parameters across species and canopy positions. Even though the leaf area density profile likely varies in this tropical forest, the SVAT model satisfactorily reproduced the eddy covariance measurements. Furthermore, the CO2 flux calculated on the assumption that Na measured in the upper canopy was distributed evenly throughout was almost the same as that taking the vertical gradient into consideration. These findings suggest that when reproducing the CO2 flux in tropical rain forests using the SVAT model, the leaf area density profile obtained from the leaf area index (LAI) measured at one point and leaf‐level physiological properties measured across species in the upper canopy are sufficient.

Phylogeny ofPgiC gene inShoreaand its closely related genera (Dipterocarpaceae), the dominant trees in Southeast Asian tropical rain forests

Dipterocarpaceae, trees that dominate tropical rain forests in Southeast Asia consist of many economically and ecologically important species. We determined partial sequences of the PgiC gene from species of Shorea, Hopea, Neobalanocarpus, and Parashorea to elucidate phylogenetic relationships among the species of these genera, which have been regarded as interrelated. The sequences generated a gene tree with better resolution than previous cpDNA trees. The PgiC tree is essentially consistent with cpDNA trees, except for the placement of Neobalanocarpus. The PgiC tree shows that Neobalanocarpus is nested within White Meranti of Shorea, whereas this genus forms a clade with Hopea in cpDNA trees. This conflict suggests that Neobalanocarpus is derived via hybridization between White Meranti of Shorea and Hopea. Species belonging to each of three timber groups (Yellow Meranti, Balau, and Red Meranti) within Shorea are monophyletic. Together they form a monophyletic clade distinct from White Meranti. Botanical sections within Red Meranti appear not to be monophyletic. An extensive number of shared polymorphisms among species and consequential lack of monophyly of intraspecific haplotypes are found in Red Meranti. Potential causes of this phenomenon, including persistence of ancestral polymorphisms and gene flow via interspecific hybridization, are discussed.

Hillslope hydrology in tropical rainforest steeplands in Brunei

Many remaining areas of tropical rainforest in south-east Asia are located on landscapes dominated by deep valleys and very steep slopes. Now that logging activities are extending into these steeplands, it is essential to understand how the natural rainforest system behaves if any kind of realistic assessment of the effects of such disturbance is to be made. This paper examines the hydrological behaviour of an undisturbed rainforest system on steep topography in the Temburong District of Brunei, north-west Borneo. The physical and hydrological properties of the regolith material are generally typical of tropical residual soils. The regolith has a clay texture and a low dry bulk density beneath a superficial litter/organic horizon. The infiltration capacity of the surface soil was several hundred mm h−1. That of the exposed mineral subsoil was an order of magnitude less, similar to the saturated hydraulic conductivity (Ksat) of around 180 mm h−1 at a depth of 150 cm. There was no indication that Ksat reduced with depth except very near the bedrock interface. Soil tensions were measured using a two-dimensional array of tensiometers on a 30° slope. During dry season conditions, infiltrating rain-water contributes to soil moisture, and drying of the soil is dominated by transpiration losses. During wet season conditions, perched water tables quickly develop during heavy rainfall, giving rise to the rapid production of return flow in ephemeral channels. No infiltration excess or saturation overland flow was observed on hillslopes away from channel margins. Subsurface storm flow combined with return flow produce stream flow hydrographs with high peak discharges and very short lag times. Storm event runoff coefficients are estimated to be as high as 40%. It is concluded that the most distinctive feature of the hydrology of this ‘steepland rainforest’ is the extremely ‘flashy’ nature of the catchment runoff regime produced by the combination of thin but very permeable regolith on steep slopes. Copyright © 2000 John Wiley & Sons, Ltd.

Preface to Changes and disturbance in tropical rainforest in South–East Asia. A Discussion Meeting held at the Royal Society on 20 and 21 January 1999

Preface to Changes and disturbance in tropical rainforest in South-East Asia. A Discussion Meeting held at The Royal Society on 20 and 21 January 1999. Organized and edited by D. M. Newbery, T. H. Clutton-Brock and G. T. Prance.

A Functional Model Describing Sapling Growth Under a Tropical Forest Canopy

The consequence of the trade-off between trunk growth and crown growth in understorey saplings is examined using a simple growth model. The model is based on published findings of interspecific variation in allometric relationships of saplings of shade-tolerant trees, their physiological parameters, and the light environment under forest canopy in south-east Asian tropical rain forests. All interspecific differences in allometries are described to reflect the difference in the allocation of dry weight between trunk stem and branch stem. In the model, branchdeveloping saplings have greater above-ground weight, larger trunk diameter, wider crown area and lower leaf area density at the same height than trunk-developing saplings. The model calculates the architecture-specific sapling growth rate, applying a classic canopy photosynthesis model to express crown photosynthesis, taking into account the self-shading within the sapling crown. Results show that the optimal allocation which maximizes sapling height growth rate for the understorey light environment is within the observed range of allocation in saplings of shade-tolerant tree species. It is proposed that fluctuation of the understorey light condition in time and space brings about the allometric variation among coexisting saplings. Key-words: Allocation, allometry, branching architecture, growth model, light environment, saplings, simulation, tropical rain forest