Pasoh Forest Reserve Research Articles

Community structure, population dynamics and biomass estimation of Bombacaceae in the 50 ha plot at Pasoh Forest Reserve, Negeri Sembilan, Malaysia

A study was carried out to determine the population dynamics and biomass estimation of Bombacaceae in the 50 ha plot at Pasoh Forest Reserve, Negeri Sembilan. Census data for the year 1985, 1990, 1990, 2000 and 2005 were obtained from the Forest Research Institute Malaysia, Kepong. The study was mainly focused on data of the year 2005. Nevertheless, comparisons between each census year were carried out to observe variations between each census. Based on the 2005 data, a total of 1,152 stems of Bombacaceae was recorded, representing three genera and five species. Durio recorded the highest number of stems with 950 individuals. The species with the highest total number of individuals was Durio griffithii with 781 individuals. Tree class size of 1.0–9.9 cm, consisting of 840 stems, accounted for 72.92% of the total abundance. The growth rate was 0.06 cm/year and the total basal area measured 0.19 m2/ha. Through distribution pattern analysis using Morisita’s Index of Dispersion (Id), Bombacaceae shows a clustered pattern distribution, with value Id = 11.46. The stimation of biomass for the year 2005 was at 2.24 t/ha, with above ground biomass at 1.98 t/ha and below ground biomass at 0.27 t/ha. Durio has the highest biomass with an estimation 2.09 t/ha, while Durio griffithii contributed to an estimated 1.01 t/ha of the biomass. A total of 237 stems were found dead (12 stems/year) and 118 new recruitments (6 stems/year) had been recorded.

Performance Analysis of Forest Canopy Height Model Generated from UAV and InSAR

Forest canopy height is a crucial parameter in ecosystem process modelling, yet research on generating canopy height models (CHMs) using photogrammetry method from UAV data remains limited compared to methods such as light detection and ranging (LiDAR). This study investigates the performance of accuracy and effectiveness of CHM generated from low-cost Unmanned Aerial Vehicle (UAV) via the photogrammetry method together with the well-known long-established Interferometric Synthetic Aperture Radar (InSAR). Leveraging advancements in UAV technology for three-dimensional land surface modelling, this research focuses on the Pasoh Research Station (nearby the Arboretum area) of Pasoh Forest Reserve in Negeri Sembilan, Malaysia. A series of images were captured at ten different UAV flying altitudes ranging from 120m to 500m above the mean sea level. Subsequently, CHMs were derived from both UAV and InSAR data, and compared against field measurements of tree height. The results indicate that UAV with a flying height below 200m can generate much more accurate results (with average height difference less than 10m) than InSAR (average height difference of 10.532m). It is noticeable that when comparing the InSAR-generated CHM to field measurements at lower altitudes (below 150m), the canopy height obtained from InSAR data is less accurate (more than 10m difference with field measurement) than the CHM obtained via UAV photogrammetry processing (only 5.353 m difference with field measurement). However, when UAV flying height is above 200m, InSAR data is performed more reliably. A 120m UAV flying height has a good potential to generate canopy height that is closer to the field measurement.

UAV-based height measurement and height–diameter model integrating taxonomic effects: exploring vertical structure of aboveground biomass and species diversity in a Malaysian tropical forest

The complex stratification of tropical forests is a key feature that directly contributes to high aboveground biomass (AGB) and species diversity. This study aimed to explore the vertical patterns of AGB and tree species diversity in the tropical forest of Pasoh Forest Reserve, Malaysia. To achieve this goal, we used a combination of field surveys and drone technology to gather data on species diversity, tree height (H), and tree diameter at breast height (D). As all trees in the 6 ha plot were tagged and identified, we used the data to classify the taxonomy and calculate species diversity indices. We used unmanned aerial vehicle-based structure-from-motion photogrammetry to develop a Digital Canopy Height Model to accurately estimate H. The collected data and previous datasets were then used to develop Bayesian height–diameter (HD) models that incorporate taxonomic effects into conventional allometric and statistical models. The best models were selected based on their performance in cross-validation and then used to estimate AGB per tree and the total AGB in the plot. Results showed that taxonomic effects at the family and genus level improved the HD models and consequent AGB estimates. The AGB was the highest in the higher layers of the forest, and AGB was largely contributed by larger trees, especially specific families such as Dipterocarpaceae, Euphorbiaceae, and Fabaceae. In contrast, species diversity was the highest in the lower layers, whereas functional diversity was the highest in the middle layers. These contrasting patterns of AGB and species diversity indicate different roles of forest stratification and layer-specific mechanisms in maintaining species diversity. This study highlights the importance of considering taxonomic effects when estimating AGB and species diversity in tropical forests. These findings underscore the need for a more comprehensive understanding of the complex stratification of tropical forests and its impact on the forest ecosystem.

Numerical Taxonomic Evaluation of Leaf Architectural Morphology of Vitex L. species (Lamiaceae Martinov) in Peninsular Malaysia

A numerical taxonomic is an algorithm method that is used to evaluate scored characters of continuous characters such as leaf architectures. Leaf architecture characters were scored from 11 Vitex species in Peninsular Malaysia (V. gamosepala, V. glabrata, V. longisepala, V. millsii, V. negundo, V. pinnata, V. quinata, V. trifolia, V. vestita, Vitex sp.1 and Vitex sp.2), one subspecies (V. trifolia subsp. litoralis) and two varieties (V. negundo var. bicolor and V. negundo var. cannabifolia) were investigated using herbarium voucher specimens and fresh specimens collected from the fieldwork. Species collected were from Pasoh Forest Reserve, Negeri Sembilan; Gunung Lambak Forest Reserve, Johor; Sungai Dara Forest Reserve, Perak; Proton City, Tanjong Malim, Perak; Gunung Lambak Forest Reserve, Johor; Cameron Highland, Pahang; Herb Walk Garden, Langkawi; and Kg. Pulau Belanga, Kota Bharu, Kelantan. All the studied Vitex species shared leaf architecture as follow: arrangement (opposite), marginal ultimate (looped), position of petiole arrangement- P.O.P.A (marginal) and petiole feature (swollen base). Specimens with single leaf type and presence of petiolule further help in distinguishing Vitex species. The scored data were analysed using Multi-Variate Statistical Package (MVSP) and Phylogenetic Analysis Using Parsimony (PAUP) softwares to obtain similarity values between species and their evolutionary relationship, respectively. Dendogram clades show an overall Gower General Similarity Coefficient (GGSc) value at 0.715 to 0.964 which indicate clear separation at genus and species level while pairwise distance between the in-group and out-group taxa analysed in the neighbour-joining tree was in between 0.26364 to 0.55455 showing that trees were constructed with strong bootstrap support with Consistency Index (CI) 0.6852 (CI) excluding uninformative character = 0.6000, Homoplasy index (HI) 0.3148 (HI excluding uninformative character = 0.4000), Retention Index (RI) 0.5802 and rescaled consistency index (RC) 0.3976. As a conclusion, high similarity in leaf architecture characters of all 11 species, one subspecies and two varieties of Vitex studied in Peninsular Malaysia suggest and support them belongs to the same genus hence supporting the taxonomic significance. This study implicate that leaf architecture morphological characters of vegetative parts can be used in identification to species, subspecies and variety level of this genus and might propose some changes to the placement of taxa hence can be devoted as an improvement for the previous Vitex study.

How drought tolerant are tropical woody crop species – turgor loss points for the five most common species in the emerging landscapes on the Malaysian Peninsular

Drought events are increasing with climate change and threaten the future of industrial plantations in Southeast Asia. Drought tolerance has been well investigated for oil palm plantations. A comparative study on the tolerance of different woody crop species is still missing. We assessed the leaf turgor loss point of five common woody crop species using osmometry. The aim was to assess possible future risks in terms of the species´ drought tolerance. The research was carried out in Simpang Pertang, Malaysia. We collected botanical material from five species, namely Acacia mangium, Hevea brasiliensis, Tectona grandis, Mangifera indica, and Elaeis guineensis. To assess the adaptation of the local tree species pool, we measured the turgor loss point of the 65 most abundant tree species in the Pasoh forest reserve for comparison. Measured species showed a wide range of drought tolerance, ranging from -2.56 MPa to -1.15 MPa and -2.46 MPa to -0.88 MPa for crop species and forest species, respectively. Under the current precipitation regime, there is less concern about the cultivation success of these species in the study area. With the predicted changes in rainfall intensity and frequency, a reduction in the productivity of woody crop plantations can be expected.

Verification of the accuracy of the recent 50 years of tree growth and long‐term change in intrinsic water‐use efficiency using xylem Δ14C and δ13C in trees in an aseasonal tropical rainforest

Abstract Growth analysis based on tree‐ring chronology is difficult in trees in aseasonal tropical rain forests, because annual growth rings may be unclear or completely absent. Fortunately, tree growth history recorded in xylem tissue is capable of providing valuable information on the responses of trees and forests to past and present environmental changes, including global warming. We have developed a new technique for aseasonal tropical forest trees which derives their growth rates from xylem Δ14C, and verified its accuracy. We also determined, from xylem δ13C, the intrinsic water‐use efficiency (iWUE) in the past 50 years. We analysed changes in xylem Δ14C and δ13C in 23 canopy trees of 12 species in 6 families growing in Pasoh Forest Reserve, Malaysia; each stem diameter at breast height (DBH) was recorded 14 times from 1969 to 2011. We found a significant positive relationship between the growth rates determined by 14C dating and the past DBH data. On the other hand, leaf‐internal CO2 (Ci) content did not change with increasing atmospheric CO2 (Ca). Thus, the iWUE increased significantly over the last 50 years in all the families and species tested. This study showed that the simultaneous measurements of xylem Δ14C and δ13C could reveal a long‐term change in tree growth and iWUE during the past 50 years with high accuracy in various species and/or individuals in aseasonal tropical rainforests exhibiting high species diversity.

Occupancy of wild southern pig-tailed macaques in intact and degraded forests in Peninsular Malaysia.

Deforestation is a major threat to terrestrial tropical ecosystems, particularly in Southeast Asia where human activities have dramatic consequences for the survival of many species. However, responses of species to anthropogenic impact are highly variable. In order to establish effective conservation strategies, it is critical to determine a species’ ability to persist in degraded habitats. Here, we used camera trapping data to provide the first insights into the temporal and spatial distribution of southern pig-tailed macaques (Macaca nemestrina, listed as ‘Vulnerable’ by the IUCN) across intact and degraded forest habitats in Peninsular Malaysia, with a particular focus on the effects of clear-cutting and selective logging on macaque occupancy. Specifically, we found a 10% decline in macaque site occupancy in the highly degraded Pasoh Forest Reserve from 2013 to 2017. This may be strongly linked to the macaques’ sensitivity to intensive disturbance through clear-cutting, which significantly increased the probability that M. nemestrina became locally extinct at a previously occupied site. However, we found no clear relationship between moderate disturbance, i.e., selective logging, and the macaques’ local extinction probability or site occupancy in the Pasoh Forest Reserve and Belum-Temengor Forest Complex. Further, an identical age and sex structure of macaques in selectively logged and completely undisturbed habitat types within the Belum-Temengor Forest Complex indicated that the macaques did not show increased mortality or declining birth rates when exposed to selective logging. Overall, this suggests that low to moderately disturbed forests may still constitute valuable habitats that support viable populations of M. nemestrina, and thus need to be protected against further degradation. Our results emphasize the significance of population monitoring through camera trapping for understanding the ability of threatened species to cope with anthropogenic disturbance. This can inform species management plans and facilitate the development of effective conservation measures to protect biodiversity.

Morphometric study of Kalophrynus palmatissimus at two forest reserves in Malaysia.

A research study on morphometrics of Kalophrynus palmatissimus (commonly known as Lowland Grainy Frog) at Ayer Hitam Forest Reserve (AHFR), Selangor and Pasoh Forest Reserve (PFR), Negeri Sembilan was carried out from 12 November 2016 to 13 September 2017. The study was to examine data on the morphometric traits of K. palmatissimus at the two forest reserves. 15 morphometric traits of K. palmatissimus that were taken by using vernier calipers. Frog surveys were done by using 15 and 18 nocturnal 400 m transect lines with an interval distance of 20 m at AHFR and PFR, respectively. The GPS coordinates for all frog samples were recorded to ensure the precise geographic location. In addition, five climatic data were recorded. The results showed that most morphometric traits in AHFR (n = 34) and PFR (n = 31) were positively correlated with each other. On the other hand, climatic factor, which was soil pH, had a significant positive influence on most of the morphometric traits (p < .01), except for tympanum diameter and upper eyelid width (p ≥ .05). Meanwhile, the temperature had a significantly negative influence on all morphometric traits (p < .01). General linear model (GLM) analysis showed that snout‐vent length (SVL) influenced most morphometric traits (F ≤ 80.86, p < .01), except for hand length (HAL: F = 0.299, p > .05). Later, it was found that the snout‐vent length of K. palmatissimus at AHFR was slightly larger than at PFR (AHFR: μ = 37.00 mm, SE = 1.16 c.f. PFR: μ = 30.29 mm, SE = 1.07). It showed that there were variations in morphometric traits of K. palmatissimus at AHFR and PFR. From PCA analysis, morphometric traits are grouped into two components for AHFR and PFR, respectively. In AHFR, head length, eye diameter, head width, internarial distance, interorbital distance, forearm length, tibia length, foot length, and thigh length were strongly correlated, while snout length and eye‐nostril distance were strongly correlated. In PFR, eye diameter, head width, internarial distance, interorbital distance, foot length, and thigh length were strongly correlated, though snout length and eye‐nostril distance were strongly correlated, hence, suggested that all morphometric traits grow simultaneously in K. palmatissimus with eye‐nostril distance (EN), and snout length (SL) growing almost simultaneously at AHFR (r = .91) and PFR (r = .97). There is still a lack of available information regarding the distribution and morphometric studies of K. palmatissimus in Malaysia, especially at AHFR and PFR. This study showed 15 different morphometric traits of K. palmatisssimus between AHFR and PFR, with K. palmatissimus at AHFR were found to be slightly larger than at PFR.

Types of Leaves Preference by Kalophrynus palmatissimus in Two Forest Reserves

A collection of leaves was carried out at each captured area of Kalophrynus palmatissimus in Ayer Hitam Forest Reserve (AHFR), Selangor and Pasoh Forest Reserve (PFR), Negeri Sembilan. K. palmatissimus is a leaf litter frog. Leaves or leaf litter provide microhabitat structures for leaf litter frogs. Leaves or leaf litter offer retreat sites for leaf litter frogs and shelters for their food sources (i.e. diversity of invertebrates). However, there have been little discussions about the types of leaves as the microhabitat structure of K. palmatissimus. The objective of this study was to investigate the types of leaves that were highly adapted by K. palmatissimus at both forest reserves. Thirty four and thirty one quadrats (2m × 2m) were established in AHFR and PFR respectively for a collection of leaves. A total of 53 and 85 leaves were recorded at AHFR and PFR respectively. Most of the leaves that were collected at both forest reserves were non-hairy/smooth leaves. The data collections in AHFR and PFR have significantly contribute to better understanding of types of leaves as the most suitable habitat and foraging sites for K. palmatissimus.

Canopy height recovery after selective logging in a lowland tropical rain forest

The effects of selective logging on canopy height were studied in a lowland tropical rain forest in Pasoh Forest Reserve, Peninsular Malaysia. Canopy height was measured in 2003 and 2011 by using an airborne light detection and ranging system and mapped on a 2.5-m grid over logged and primary forest plots. The logged forest plot was in an area where a selective logging operation had been conducted in 1958, whereas the primary forest plot has no trace of any major human-induced disturbances. The average canopy height in the logged forest plot increased from 23.6 m (2003) to 25.8 m (2011), but both of these heights were still significantly lower (P < 0.0001) than in those in the primary forest plot (28.7 m in 2003 and 30.4 m in 2011). The coefficient of variation and canopy height diversity (H′) were also lower in the logged forest plot, suggesting that the highly heterogeneous canopy height commonly seen in the primary forest in this region had not fully recovered even 53 years after the logging operation. Simulation analysis revealed that it will take at least another 16 years from the last canopy mapping (2011) for full recovery.

Data paper: Long‐term litter production in a lowland dipterocarp forest, Peninsular Malaysia from 1992 to 2017

Tropical rainforests in Southeast Asia dominated by Dipterocarpaceae show a unique reproductive event, general flowering. This paper records long‐term seed production of a tropical rainforest in Pasoh Forest Reserve, Peninsular Malaysia. Study site is a lowland dipterocarp forest dominated by Dipterocarpaceae and Fabaceae. Seed and other litter production data are essential for analyzing general flowering and evaluating net primary production (NPP) of rainforest ecosystems under climate change. Unfortunately, there is a lack of long‐term litter production data in Dipterocarp forests. This paper presents such a long‐term litter data from 1992 to 2017. We collected litter samples every month from May 1992 to December 2017 in Pasoh F.R., Peninsular Malaysia (2°59′N, 102°18′E, 120–152 m a.s.l.). Litter was collected using 100 litter traps spaced evenly within a 2‐ha core area of the 6‐ha study plot. Each litter trap was made of 1 mm mesh with a circular area of 0.5 m2 from May 8, 1992 to December 22, 1998. Then litter trap was changed to a square type with 4 mm mesh until now. Litter samples were collected and separated to leaf, flower, seed and others (debris). After sorting litter samples were dried at 85°C for 48 hr and weighed. Seeds and flowers were separated according to tentative morphological types and identified. This data paper contains two data sets. Litter data set contains weight of each litter fractions. Seed data set contains number and weight of morphological seed types and identified scientific name.

Discovery of Lymantini weevils (Coleoptera: Curculionidae: Molytinae) outside the Americas: Devernodes, a new genus for five new species from Southeast Asia.

This paper reports a new weevil genus Devernodes gen. n. established for five new species from Southeast Asia: D. alkippe sp. n. (China: Mt. Emei), D. asteria sp. n. (Vietnam: Tam Dao), D. chthonia sp. n. (Vietnam: Tam Dao; the type species), D. drimo sp. n. (Malaysia: Pasoh Forest Reserve) and D. methone sp. n. (Malaysia: Tanah Rata). All Devernodes are wingless and inhabit the forest leaf litter. Adult Devernodes share a combination of two head characters unique among weevils in Asia: antenna with apparently unsegmented club and 6-segmented antennal funicle, as well as strong constriction separating the eye-bearing rostrum from the head capsule. To test monophyly and investigate phylogenetic relationships of Devernodes, Maximum Likelihood phylogenetic analysis was undertaken using parts of mitochondrial (COI) and nuclear ribosomal (28S) genes, as well as the nuclear internal transcribed spacer (ITS2) from 14 Devernodes and 55 outgroup Curculionidae specimens. Results strongly corroborated monophyly of Devernodes and did not suggest its realistic sister-group. The new genus is assigned to the molytine tribe Lymantini (not represented in the DNA analysis) based on two potential synapomorphies: head markedly constricted behind eyes and presence of undivided female hemisternites IX (= "merged coxite and stylus"). Thus interpreted, Devernodes is the twelfth nominal genus of Lymantini and the first record of the tribe outside of the Americas. All original data (localities, DNA sequences, specimen images) are available online in public datasets dx.doi.org/10.5883/DS-DEVERNO1 and dx.doi.org/10.5883/DS-DEVERNO2.

Dynamics of Tree Species Diversity in Unlogged and Selectively Logged Malaysian Forests

Selective logging that is commonly conducted in tropical forests may change tree species diversity. In rarely disturbed tropical forests, locally rare species exhibit higher survival rates. If this non–random process occurs in a logged forest, the forest will rapidly recover its tree species diversity. Here we determined whether a forest in the Pasoh Forest Reserve, Malaysia, which was selectively logged 40 years ago, recovered its original species diversity (species richness and composition). To explore this, we compared the dynamics of secies diversity between unlogged forest plot (18.6 ha) and logged forest plot (5.4 ha). We found that 40 years are not sufficient to recover species diversity after logging. Unlike unlogged forests, tree deaths and recruitments did not contribute to increased diversity in the selectively logged forests. Our results predict that selectively logged forests require a longer time at least than our observing period (40 years) to regain their diversity.

Evapotranspiration and water source of a tropical rainforest in peninsular Malaysia.

To evaluate water use and the supporting water source of a tropical rainforest, a 4‐year assessment of evapotranspiration (ET) was conducted in Pasoh Forest Reserve, a lowland dipterocarp forest in Peninsular Malaysia. The eddy covariance method and isotope signals of rain, plant, soil, and stream waters were used to determine forest water sources under different moisture conditions. Four sampling events were conducted to collect soil and plant twig samples in wet, moderate, dry, and very dry conditions for the identification of isotopic signals. Annual ET from 2012 to 2015 was quite stable with an average of 1,182 ± 26 mm, and a substantial daily ET was observed even during drought periods, although some decline was observed, corresponding with volumetric soil water content. During the wet period, water for ET was supplied from the surface soil layer between 0 and 0.5 m, whereas in the dry period, approximately 50% to 90% was supplied from the deeper soil layer below 0.5‐m depth, originating from water precipitated several months previously at this forest. Isotope signatures demonstrated that the water sources of the plants, soil, and stream were all different. Water in plants was often different from soil water, probably because plant water came from a different source than water that was strongly bound to the soil particles. Plants showed no preference for soil depth with their size, whereas the existence of storage water in the xylem was suggested. The evapotranspiration at this forest is balanced and maintained using most of the available water sources except for a proportion of rapid response run‐off.

Quantifying the role of wood density in explaining interspecific variation in growth of tropical trees

AbstractAimTo evaluate how wood density relates to tree growth rates in simple models and two tropical forests.LocationBarro Colorado Island, Panama; and Pasoh Forest Reserve, Malaysia.Time Period1986–2010.Major Taxa StudiedTrees.MethodsWe derived expected relationships of wood density with diameter growth at a given diameter under a null hypothesis that aboveground biomass growth is independent of wood density, and an alternative hypothesis that biomass growth scales with crown area, which itself increases with wood density. We tested these assumptions and predictions through analyses of interspecific relationships of wood density with height, crown area and diameter growth at constant diameter in two tropical forests.ResultsHeight was unrelated to wood density, whereas crown areas showed a slightly positive relationship to wood density. Thus, the expected exponent of diameter growth with wood density was equal to minus one under the null hypothesis, and equal to the exponent of crown area with wood density minus one under the alternative hypothesis. Empirical relationships of diameter growth and biomass growth with wood density were broadly consistent with the null hypothesis that biomass growth is unrelated to wood density at both sites, except in trees &lt; 13 cm in diameter at Barro Colorado Island, which showed more negative relationships.Main conclusionsAlthough most previous analyses of growth with wood density have examined linear relationships, simple models suggest that both tree diameter growth and tree biomass growth are power functions of wood density. Analyses in two tropical forests showed that aboveground biomass growth was approximately constant with wood density, and thus, that diameter growth was inversely proportional to wood density, for most tree sizes, although confidence intervals on the scaling exponents were broad. More negative relationships of growth with wood density at small sizes might reflect differential environmental filtering, in which higher wood density trees are found in less favourable understorey environments.

Species‐specific flowering cues among general flowering Shorea species at the Pasoh Research Forest, Malaysia

Abstract In a unique phenomenon restricted to the ever wet forests of Southeast Asia, hundreds of species from dozens of plant families reproduce synchronously at irregular, multi‐year intervals. The proximate environmental cues that synchronize these general flowering events have not been evaluated systematically because there have been no long‐term, high temporal resolution, species‐level records from the region. We present 13 years of weekly flowering records for five Shorea species as well as daily temperature and rainfall records from the Pasoh Forest Reserve, Peninsular Malaysia. We constructed models to evaluate hypothesized relationships between flowering and cool temperature, drought, and additive and synergistic effects of cool temperature and drought for each species. Model parameters include periods of time for floral cue accumulation and flower development and temperature and/or rainfall thresholds required for floral initiation. Parameters estimated using flowering observations from 2001 to 2011 were used to forecast flowering for 2011–2014. We show that drought and cool temperatures acting synergistically best explain the timing of flowering events for all Shorea species in the section Mutica and forecast the largest general flowering event accurately. Periods estimated for signal accumulation ranged from 54 to 90 days among species. Periods estimated for flowers to develop ranged between 43 and 96 days and closely followed the interspecific sequence of flowering in the Shorea species. Drought and temperature thresholds also varied among species, with Shorea maxwelliana requiring the most severe drought and Shorea leprosula the lowest temperatures. Synthesis. Our results indicate that cool temperatures and low rainfall occurring on seasonal time‐scales of about 2–3 months rather than brief cold snaps or brief droughts best explain general flowering in Shorea species at the Pasoh Forest Reserve. Low rainfall is equally likely in winter (December–February) and summer (July–August) and cool temperatures are most likely in winter at Pasoh, which explains why general flowering events are restricted to spring and fall, with more frequent and stronger flowering in spring. In addition, species‐specific sensitivity to environmental cues suggests that future climate change will have differential impacts on the frequency of reproduction, with potential consequences for regeneration of these dominant species of lowland tropical forests.

Studies on the distribution and ecological role of termites in a lowland rain forest of West Malaysia, 3: Distribution and abundance of termites in Pasoh Forest Reserve.

Studies on the distribution and ecological role of termites in a lowland rain forest of West Malaysia, 3: Distribution and abundance of termites in Pasoh Forest Reserve.

選択伐採が熱帯林生態系に及ぼす長期的な影響～マレーシア、パソ保護林の 事例から～（山田俊弘）へのコメント

選択伐採が熱帯林生態系に及ぼす長期的な影響～マレーシア、パソ保護林の 事例から～（山田俊弘）へのコメント

Long-term effects of selective logging on dipterocarp populations in the Pasoh Forest Reserve, Malaysia

Background: Selective logging alters tree growth, mortality and recruitment, and the subsequent population dynamics of trees. However, little information is available on how tree populations reduce local extinction in logged forests.Aims: We evaluated the effects of selective logging on tree performance and population dynamics of five dominant dipterocarp species in the Pasoh Forest Reserve, Malaysia.Methods: We used demographic data derived from a forest that was selectively logged in 1958 as well as those from an unlogged primary forest and constructed population transition matrix models to project the population dynamics.Results: The dipterocarp species studied showed minor differences in mortality and diameter growth, but there was a large difference in recruitment between logged and unlogged forest; populations in the logged forest had 10 times slower recruitment rates into the smallest size class than those in the primary forest. Population size structures differed between the two forest types but, despite a large difference in the recruitment rates, there were only minor differences in both asymptotic- and matrix-projected population growth rates.Conclusions: A single selective logging event had only minor impacts on the growth rates of dipterocarp trees in the Pasoh forest. But at the same time it had a large impact on the size structure of the dipterocarp populations through a reduction in recruitment showing that the impacts of selective logging are still seen on dipterocarp population after 50 years.

Long-term changes in liana loads and tree dynamics in a Malaysian forest.

The importance of lianas through time and their effect on tree reproduction are evaluated for the first time in a Southeast Asian Dipterocarp forest. We quantified flower and seed production by lianas and trees for 13 years, assessed liana loads in the crowns of all trees larger than 30 cm in diameter at breast height (1.3 m) in 2002 and 2014, and assessed levels of reproduction for the same trees during a strong general flowering event in 2014 for the 50-ha forest dynamics plot at the Pasoh Forest Reserve, Malaysia. General flowering refers to synchronous reproduction by hundreds of plant species at irregular, multiyear intervals and only occurs in Southeast Asian Dipterocarp forests. Overall, lianas were present in 50% of tree crowns and comprised 31% of flower production and 46% of seed production. Lianas reduced growth, survival, and reproduction by their host trees. Lianas were less frequent in canopy- emergent trees, Dipterocarps comprised a disproportionately large proportion of canopy emergents, and, as a consequence, lianas were less frequent in Dipterocarps than in trees from other plant families. Lianas infested the crowns of significantly fewer trees in 2014 (47.9%) than in 2002 (52.3%); however, the decrease was restricted to trees with the lightest liana loads and sample sizes and statistical power were enormous. Lianas comprised a stable proportion of flower production and a highly variable proportion of seed production from 2002 through 2013. We conclude lianas have a huge impact on trees in this forest and were a stable component of the forest between 2002 and 2014. The emergent habit and associated ability to avoid lianas might contribute to the success of the Dipterocarpaceae.