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Vatica cauliflora P.S. Ashton (Dipterocarpaceae) is a threatened tree species endemic to Kapuas Hulu District, West Kalimantan Province, Indonesia. The species is only known from the type specimen collected in 1953. After this first collection, there was no record confirming the presence of this tree in its natural habitat. Our recent surveys in 2019 and 2020 located 179 individuals of the species in six unprotected locations. The population's size structure is dominated (62.6%) by young individuals within the 0–5 cm diameter class. Our surveys also showed that the habitat of V. cauliflora is degraded as a result of the negative effects of agriculture and logging. Assessment with the IUCN Red List criteria indicates that V. cauliflora should be categorized as Critically Endangered.

Dipterocarpaceae, a dominant family of trees in South-East Asian tropical forests, are remarkable in that they exhibit supra-annual mass-flowering events. The flowering patterns are related to the El Niño Southern Oscillation, but the mechanism that precipitates mass-flowering is still debated. Here, we test if a cumulative-trigger model that tracks resource availability, specifically light, may better explain dipterocarp phenology than a direct-environmental-trigger mechanism. Using 11 flowering time series with an average length of 29 y and variety of candidate predictor variables (precipitation, cloud cover, minimum temperature and El Niño indices) we could not find a plausible direct-environmental-trigger (median AUCs across regions from 0.53 to 0.57 indicating near random predictions). The cumulative-trigger model based on El Niño indices showed better predictive results (AUC 0.67), which could further be improved by resetting the resource at known flowering events (AUC 0.76). Additional support for a cumulative-trigger model comes from the observation that regional differences in the time of year of peak flowering correspond to where El Niño effects are strongest. We conclude that cumulative resource tracking is an evolutionary plausible trigger mechanism that has other primary evolutionary advantages, such as predator satiation.

Monodominance in the tropics is often seen as an unusual phenomenon due to the normally high diversity in tropical rain forests. Here we studied Parashorea chinensis H. Wang (Dipterocarpaceae) in a seasonal tropical forest in south-west China, to elucidate the mechanisms behind its monodominance. Twenty-eight 20 × 20-m plots were established in monodominant and mixed forest in Xishuangbanna, Yunnan province. All individuals ≥1 cm stem diameter and 16 soil variables were measured. Parashorea chinensis forest had a significantly higher mean tree dbh compared with mixed forest. Diversity did not differ significantly between the two forest types. However, within monodominant patches, all diversity indices decreased with an increase in P. chinensis dominance. Floristic composition of P. chinensis forest did differ significantly from the mixed forest. These differences were associated with more fertile soils (significantly higher pH, Mn, K and lower carbon pools and C:N ratio) in the P. chinensis forest than the mixed forest. In contrast to current paradigms, this monodominant species is not associated with infertile, but with fertile soils. Parashorea chinensis seems to be especially associated with high manganese concentrations which it can tolerate, and with edaphic conditions (water, K) that allow this tall and exposed emergent species to maintain its water balance. This is in contrast with most previous studies on monodominance in the tropics that found either no effect of soil properties, or predict associations with nutrient-poor soils.

The family Dipterocarpaceae includes 470 tree species from 13 genera in South and South-East Asian tropical forests (Ashton 1982). Many dipterocarp species in aseasonal lowland rain forests of western Malesia flower synchronously during masting (or general flowering) events, which usually occur at irregular intervals of 2–10 y (Ashton et al. 1988). Very few individuals flower at other times, and successful recruitment of seedlings is limited to those masting events (Ashton et al. 1988, Curran et al. 1999).

Trees of the family Dipterocarpaceae dominate the emergent canopy of most lowland rain forests in Asia (Ashton et al. 1988). The family is, therefore, one of the most ecologically important in South-East Asia. Shorea curtisii Dyer ex King is the most common tree species in the hill dipterocarp forests of Peninsular Malaysia (Burgess 1975, Symington 2004), and is considered a key species for the dynamics of such forests. Currently, most Malaysian hill forests are selectively logged. Trees over 50 cm dbh are harvested, and any subsequent harvests depend on the remaining smaller trees. Such selective logging takes no account of seedling regeneration. Hence, subsequent timber harvests rely on trees derived from the seedlings that are already present and future seeds produced by the residual trees (Appanah & Mohd. Rasol 1994). Existing seedlings of S. curtisii in the forest, therefore, play a significant role in the dynamics of the hill forest. However, the conditions that constitute a suitable habitat for S. curtisii seedling establishment and survival remain unknown.

Spatial distribution patterns and habitat associations of Fagaceae species in a Fagaceae-codominated hill forest in Sumatra were investigated. Ten Fagaceae species believed to be zoochorous (animal-dispersed seed) and five codominant canopy and emergent anemochorous (wind-dispersed seed) species from Anacardiaceae and Dipterocarpaceae were studied. Five Fagaceae species and all codominant anemochorous species were significantly aggregated while the other five Fagaceae species showed a random distribution pattern. The median distance of small saplings from the nearest reproductively mature tree tended to be shorter for aggregated species than spatially random species. This implied that some Fagaceae species dispersed over longer distances than anemochorous species. Relationships between four habitat variables and distribution of the target species were examined with torus-translation tests. ThreeQuercusand oneLithocarpusspecies showed positive habitat associations. TwoQuercusspecies aggregated at the preferred habitat, but the others were randomly distributed. Thus tree species with specific habitat preference do not only aggregate at the preferred habitat. The three ridge-specialistQuercusspecies showed gradual changes in habitat association, which could reflect avoidance of competition among the species. Most of theLithocarpusspecies showed little correlation with habitat variables. Coexistence of the threeQuercusspecies partly reflected subtle differences in topographical preferences. Distribution of five of the sixLithocarpusspecies was unrelated to topography, so other mechanisms must be sought to account for the maintenance of coexistence in this species-rich genus.

Seedlings of five species in the Dipterocarpaceae were grown in experimental plots in Sabah, Malaysia. These were sited both in gaps and understorey and on alluvial and sandstone soils. Half of all seedlings were provided with a complete fertilizer. Herbivore damage levels were recorded on over 25 000 individual leaves in four surveys over the course of 2 y. Rates of herbivory were lower on mature leaves (0.07–0.8% leaf area mo−1 among species) than new leaves (2.1–4.4% leaf area mo−1). There were no overall effects of light conditions, soil type, fertilizer treatment or time on rates of herbivory. The only consistent source of variation was that between species, with the three alluvial-specialist species suffering higher rates of damage than the two sandstone-specialists. Mature leaves of alluvial species received greater damage in sandstone soils, whereas sandstone species were damaged at equivalent rates on both soil types. New leaves were more damaged on their native soil type. Published herbivory rates vary in the timescales and methods of measurement. Nevertheless, the few comparable studies confirm that herbivory rates on seedlings in tropical rain forests are remarkably constant over time and across experimental treatments.

A prediction of the hypothesis that niche processes control plant species distributions across edaphic gradients is that pairwise comparisons of related species on contrasting soils should show consistent patterns of trait divergence. This hypothesis was tested in lowland Bornean rain forest by combining measurements of leaf traits, soil nutrients and the distribution of tree species in the Dipterocarpaceae across a nutrient gradient. Nine species were studied, comprising four related pairs in Shorea (phylogenetic independent contrasts; PICs) and one habitat generalist (Dipterocarpus sublamellatus). Lamina area, specific leaf area (SLA), leaf nitrogen (N) and phosphorus (P) were measured for ∼10 saplings of each species; habitat associations were defined as a continuous function of soil nutrients and categorically in relation to substrate. Species distributions and traits varied significantly with soil nutrients. When all species were pooled, SLA and leaf P increased significantly with species' distribution across the nutrient gradient; leaf N showed the same trend. Trait shifts with habitat were stronger and more pervasive when habitat was defined categorically – in all four PICs, rich-soil specialists had larger leaves, higher SLA, leaf N and P, and lower N:P ratios. Trait shifts with habitat at least partly reflect intrinsic differences between species. Within Shorea, variation in lamina area and N:P ratio were more strongly related to phylogeny than habitat, whereas the reverse held for SLA and leaf P. Phylogeny also influenced the extent of trait divergence between related species on different soils, and patterns of trait correlation within lineages. Results support the hypothesis that niche processes influence the distribution of species and traits in lowland tropical tree communities, and highlight the value of phylogenetic information for increasing the power of comparative studies.

To investigate whether seedlings of ten dipterocarp species differed significantly in terms of growth and mortality or whether species were not significantly different and could be considered ecologically similar, seedlings were grown, two per pot, in two experiments: (1) where the two seedlings were of equal height (30 cm); and (2) where one seedling was 10 cm shorter than the other. Seedlings were grown in a shade house with 15% above-canopy light in a 50:50 forest soil–sand mixture and were watered frequently; pots were placed so that seedling density was 130 seedlings m−2 of ground. In the first experiment there were 45 pairwise combinations of species when seedlings were 30 cm tall (AB, AC, AD,…. BC, BD…IJ; where A, B, C…J signify different species); each combination was replicated 10 times so there were 450 pots with 900 seedlings. In the second experiment there were 100 pairwise combinations of species and size e.g. Aa (30 cm A with 20 cm a), Ab (30 cm A with 20 cm b), each combination was replicated 10 times hence there were 1000 pots with 2000 seedlings. After 22 mo 79% of the initial 2900 seedlings survived; on average they had grown 42 cm (i.e. to 72 cm tall from their initial 30 cm). The most frequent outcome of competition-trials between different sized individuals (784 of 1000 trials) was that the initially taller seedling of each pair ‘won’ (it was the taller or surviving seedling). When 900 of these trials (setting aside, Aa, Bb, Cc etc.) were analysed as 45 comparisons between species with different sized individuals (Ab and aB are one interspecific comparison for these purposes), initial height determined the outcome in 23 cases (even in some competitions between light hardwood species and heavy hardwood species); in 6 cases a species (mostly light hardwoods) behaved as a ‘dominant’ – they usually won even if they were smaller initially. We found few significant differences between species in: initial seedling heights; leaf nitrogen concentrations; and specific leaf areas when they were grown in similar conditions, and these attributes were not correlated with growth rates. The similarity of seedlings of different species meant that often a height difference of just 10 cm was enough to determine the outcome of a pairwise competition-trial in high seedling densities and light equivalent to that in forest gaps.

The induction of carbon-based secondary metabolites in leaves following damage has been proposed to be a result of a shift in the carbon:nutrient balance, when growth is limited by nutrients in relation to carbon. Here we test this hypothesis using seedlings of a tropical tree, Shorea leprosula (Dipterocarpaceae). In the short term, we analysed the phenolic content of leaves 7 d after damage on seedlings grown under differing light and nutrient treatments. In the long term, we examined the effect of nutrients, over 12 mo, on leaf phenolic concentration and seedling growth. In both the long and short term, levels of phenolics increased in damaged leaves under low nutrient treatments. No changes in leaf phenolics were detected under high nutrient regimes, or in the short term under low light. In addition, it was found that defoliation of seedlings in high-nutrient environments led to greater rates of leaf production than in undamaged seedlings, suggesting compensation.

Spatial variation in canopy structure induces highly variable patterns of light availability for juveniles and understorey trees (Nicotra et al. 1999, Oberbauer et al. 1988, Tang et al. 1999). In the heterogeneous light environment, plasticity in resource use is essential for survival of juveniles and hence maintenance of populations (Valladares et al. 2000). One of the most striking characteristics of plants in their response to a given resource availability is their capacity to change morphological traits (Kiippers 1994). Previous studies have attempted to understand the significance of morphological adaptations in their contribution to competitive ability, focusing on crown form (Kohyama 1987, Sterck et al. 2003), branching pattern (King 1998), shoot architecture (Canham 1988) and leaf shape (King & Maindonald 1999, Takenaka 1994, Yamada et al. 2000). Several studies have investigated the changes in morphology of saplings or seedlings growing under different light availability across canopy gaps (Ackerly & Bazzaz 1995, King 1994, Valladares & Pearcy 1998). However, the phenotypic plasticity in morphology of saplings adapting to the fluctuation of light availability has been investigated less (Blundell & Peart 2001, Poorter & Werger 1999). We evaluated the morphological plasticity of Shorea parvistipulata (Dipterocarpaceae, a canopy species) saplings growing under different levels of canopy openness in the Kubah National Park, Sarawak, Malaysia (13 7'N, 110009'E). The mean annual precipitation is extremely high, 6000-7000 mm (Hazebroek & Marshidi 2000). The mean daily temperature during the period between February to July in 1999 was 26.7 C. The study site is covered by mixed dipterocarp forest. All saplings of Shorea parvistipulata in a 30 x 30-m study plot were investigated in March 1998 and March 1999. The saplings of S. parvistipulata showed two forms: unbranched and branched. Dependence of tree morphology, such as leaf shape and crown form, on life stage has been reported in previous studies (Osada & Takeda 2003, Yamada & Suzuki 1996). There were 80 saplings in the study plot in March 1998; 61 were unbranched (76%) and 19 were branched (24%). Fortysix unbranched (75%) and 18 branched saplings (95%) survived to the end of the research period. To quantify the light environment, hemispherical photographs were taken with a fish-eye lens (Nikon 8 mm F2.8, Tokyo, Japan) directly above each sapling, and at the corners of a 5 x 5-m grid at 1.5 m height within the study plot. The canopy openness above surviving saplings was significantly greater than the average condition on the forest floor (Figure 1). The canopy openness for the saplings that died during the study period was lower than that for the surviving saplings (medians 3.74% and 4.59%, respectively, U-test, U= 242.5, P 0.3 5). Branched saplings were taller than unbranched saplings (medians were 63.4 cm and 35.6 cm, respectively, U-test, U= 60.5, P 0.21). Logistic regression analysis was used to quantify the probability of a sapling dying (X2 = 13.6, df= 2, P < 0.005) versus size and light availability. For 1Corresponding author. Email: enoki@agr.u-ryukyu.ac.jp

Some tree species exhibit large year-to-year variation in seed production, a phenomenon known as masting (Kelly 1994, Kelly & Sork 2002). Even in tropical rain forests, in which the climate is suitable for plant growth all year round with little seasonal variation (Whitmore 1998), there are many reports of masting (Appanah 1993, Hart 1995, Newbery et al. 1998, Newstrom et al. 1994, Wheelwright 1986). In particular, Dipterocarpaceae, the dominant family in lowland mixed dipterocarp forests in South-East Asia, undergo mast fruiting following mass-flowering with strong interspecific synchronization in aseasonal western Malesia (Appanah 1985, 1993; Ashton 1989, Ashton et al. 1988, Curran et al. 1999, Janzen 1974, Medway 1972, Sakai et al. 1999, Whitmore 1998, Wood 1956). In mixed-dipterocarp forests, dipterocarp species contribute more than 70% of the canopy biomass (Bruenig 1996, Curran & Leighton 2000). Masting of dipterocarp species is therefore likely to have a major impact on animal populations, and also on the nutrient cycle in such forest ecosystems by causing fluctuations in the availability of resources (Sakai 2002).

Patterns of leaf phenological diversity were documented in nine key tree species of a tropical deciduous forest in the Vindhyan region of India. Monthly leaf counts on 160 tagged twigs on ten individuals of each species were made through two annual cycles. Tree species exhibited a gradient of deciduousness (∼leafless duration), ranging from semi-evergreen species (entire population never becoming leafless) to 7-mo-deciduous species. The semi-evergreen species initiated leaf flush (bud break of vegetative bud) earlier around the spring equinox. In all deciduous tree species synchronous leaf-flush initiation, with low inter-annual variability, occurred during the hot dry summer (May–June, day temperature >40 °C), prior to the onset of the rainy season. Based on the quantification of leafless period, leaf-flush duration, and leaf strategy index (leaf-flush rate/leaf-fall rate, proposed in this study) in different species, four plant functional types were recognized: (a) semi-evergreen, spring flushing, showing leaf exchange, with mean leafless period 8 d, leaf-flush duration 6–7 mo and leaf strategy index Shorea robusta); (b) 0.5−Anogeissus latifolia, Diospyros melanoxylon and Hardwickia binata); (c) 2–4-mo-deciduous, summer flushing, leafless period 2–3 mo, leaf-flush duration 4–5 mo, and leaf strategy index >0.8−Acacia catechu, Lagerstroemia parviflora and Terminalia tomentosa); and (d) >4-mo-deciduous, summer flushing, leafless period >4–7 mo, leaf-flush duration 3–4 mo, and leaf strategy index 1.0 (Boswellia serrata and Lannea coromandelica). Conspecific trees showed asynchrony with respect to leaf-flush completion, initiation and completion of leaf-fall, and extent of leafless period. Leaf strategy index (indicating rate of resource use and conservation) was strongly related with the leafless period in different species (r=0.82) and can serve as a useful index in leaf phenological studies and classification of plant functional types.

Dryobalanops rappa (Dipterocarpaceae), a dominant tree in wetland forests in Borneo, often produces vegetative sprouts in its juvenile stages (trees less than 25 m in height), a characteristic that is believed to be rare in tropical forest trees. We investigated the growth characteristics of this species in a tropical forest in Merimbun Heritage Park, Brunei, to verify the hypothesis that the vigorous sprouting ability enables it to grow in a wetland forest with soft soils that promote stem decumbency and to assess the adaptive significance of vegetative sprouting in the context of its regeneration. Reproductively mature trees developed buttresses and were rarely decumbent. However, if they became decumbent, they died without sprouting. Juvenile trees were frequently decumbent, and their decumbent shoots sprouted vegetatively. Therefore, vegetative sprouting acted as a countermeasure to decumbency and death on the soft wetland soil. A decumbent shoot produced only one sprout in most cases. Decumbent shoots grew little and eventually died, but new sprouts showed rapid growth. This suggests that there is translocation of resources from decumbent shoots to sprouts. If decumbency occurs, a D. rappa genet ramifies into sprouts, and helps sustain the population in the wetland environment. This vegetative life history strategy is important for regeneration in wetland forests with soft soil.

Rainfall fluctuation influences the physiology and leaf production of the trees in tropical rain forests (Burslem et al. 1996, Condit et al. 1995, Reekie & Wayne 1992, Reich 1995), and consequently it may have an impact on the community of herbivores that depend on forest trees for their food resources (Aide 1988, 1992; Basset 1991, Coley 1998, Lowman 1985, van Schaik et al. 1993).

In the first 3 mo of 1998, an aseasonal tropical rain forest at Lambir Hills National Park on the north-west coast of Borneo suffered an unusually severe drought. Extreme climatic events such as this one are expected to influence tree population structure and community dynamics through differential effects on growth and mortality. The demo- graphics of seedlings of seven shade-tolerant tree species, including two dipterocarps, during this severe drought were contrasted with baseline demographic data from two earlier census intervals, one of which included a slight drought, and one of which included no drought. Hemispherical photographs were used to document an opening of the canopy that resulted from the dieback and mortality of large trees during the severe 1998 drought. Seedlings that experienced an increase in canopy openness were less likely to die than other seedlings. Rates of mortality and height loss were significantly increased in association with drought. The overall mortality rates during the severe drought and slight drought census intervals were 8.2% y −1 and 7.3% y −1 respectively, compared with 4.9% y −1 for the non-drought census interval. The incidence of height loss during the severe drought census interval was 27.5%, compared with rates of 11.7% and 20.1% for earlier census intervals. Dipterocarp species were less affected than some non-dipterocarp species, and the smallest seedlings suffered the greatest impact. If droughts in this region continue to increase in intensity and severity, they may ultimately cause a change in the species population densities and stand structure of the understorey seedling community of this rain forest.

We investigated the spatial distribution of fruiting in Dryobalanops aromatica (Dipterocarpaceae), a mast-seeding emergent tree that is found in the tropical rain forests of Borneo. Of 393 adults (diameter at breast height (dbh) > 30 cm) in a 52-ha area, 143 (36.4%) individuals fruited. A second-order spatial analysis, based on Ripley's K-function, revealed that fruiting trees were significantly (P < 0.05) aggregated with respect to the total population over distances of 15-115 m. Thus, the spatial distribution of fruiting trees was more aggregated than expected from the adult tree distribution, which itself was aggregated within the study plot. Logistic regression analysis showed that fruiting trees had a significantly greater dbh and were surrounded by more conspecific adults per ha than non-fruiting individuals. Moreover, fruiting trees were found at higher elevations, on steeper slopes, and on sandy rather than clayey soils. In contrast, annual diameter growth, adult density over areas < 1 ha, and slope convexity did not significantly affect fruiting probability. The ratio of seedling (20 cm ≤ h < 60 cm) and sapling (60 cm ≤ h < 300 cm) density to adult density was higher in sites at higher elevations, on steeper slopes, and on sandy soils than that for lower elevations, flat slopes and clayey soils. This suggests that the aggregation of fruiting trees occurred not only at the time of the study, but that it had occurred repeatedly in the past, at the high-elevation, steep-sloped, sandy sites. Thus, site conditions probably affect the dynamics and spatial structure of local populations through differences in fruiting frequency among trees experiencing different site conditions.

Using 14C dating, the life span and growth rate of Borneo ironwood (Eusideroxylon zwageri, Lauraceae), which is a canopy tree species with extremely durable and decay-resistant wood distributed in tropical rain forests of South-East Asia, were studied. Timber segments collected from 15 logged stumps in Kubah National Park, Sarawak, Malaysia, were analysed by accelerator mass spectrometry and the obtained data were calibrated to determine the age of individuals. The 14C dating turned out to be an effective method for estimating ages of long-lived trees, such as E. zwageri, in the aseasonal tropics because the estimated error was small compared with estimated age. We found that E. zwageri can live more than 1000 y and that the growth rate of this species was very slow, with a mean radial growth rate of 0·058 cm y-1. The life span was much greater and the growth rate was much slower than those observed or estimated for trees of Dipterocarpaceae, the dominant family in this tropical forest. The long life span of this species may be caused by wood durability with a high specific gravity and abundant defensive compounds. Given equal carbon allocation, the high density and carbon-based defensive compounds may result in a reduced growth rate.

The population dynamics of 8500 shade-tolerant tree seedlings of 13 tree species were followed for 10 years at rain forests in Lambir Hills National Park and Bako National Park, Malaysian Borneo. Since these dipterocarp forests have lower rates of canopy gap formation than do rain forests elsewhere, tree seedling biology was predicted to differ. Approximately 50% of seedlings present in 1986 were still alive in 1996. Seven out of thirteen had seedling populations composed predominantly of individuals that were at least 10 years old. These seedlings can undergo alternating periods of relatively rapid and slow growth. Many seedlings that grew rapidly in the first census interval survived through a period of suppression in the second census interval, and conversely many seedlings with a history of suppression had exceptionally high growth in the final census interval. Seedlings of South-East Asian forest tree species are long-lived and appear to be adapted to long periods of suppression in the understorey.

The influence of herbivory on dipterocarp seedling growth and survival in Bornean primary lowland forest understorey during and after the 1997–8 El Niño-Southern Oscillation was investigated. During the drought, a coleopteran (Scolytidae) root borer attacked dipterocarp seedlings, primarily of the genus Parashorea. Infestation was spatially heterogeneous on a large (c. 100 m) scale. Attack rate decreased with plant vigour within infested areas. Experiments showed that root damage was fatal under drought conditions, but not after rain. Defoliation and apical meristem removal did not increase mortality. The spatio-temporal heterogeneity of herbivore outbreaks and difficulties involved in experimenting with root herbivores limit the power of such short-term investigations. However, the study shows that herbivores can cause differential mortality between species, and can therefore influence dipterocarp regeneration dynamics. The effect of herbivory depends on the plant organ attacked and interactions with other stresses such as drought. El Niño-related droughts are increasing in frequency in South-East Asian rain forests, which may lead to increased numbers of herbivore outbreaks and greater seedling mortality due to these factors.

Seed dispersal is the predominant mobile stage for sessile plants, and critically affects the distribution patterns of the species (Nathan & Muller-Landau 2000). Thus, seed dispersal patterns are important in understanding the population dynamics of the species.

Wood pieces of a heavy hardwood Neobalanocarpus heimii (King) P. S. Ashton and a light hardwood Shorea macroptera Dyer were used in decomposition experiments with termite-exclusion and control trays on the forest floor of the Pasoh Forest Reserve, West Malaysia to determine effects of wood quality on termite-mediated wood decay. Shorea macroptera had a significant loss of C in the presence of termites while Neobalanocarpus heimii showed no significant termite effect. Neobalanocarpus heimii and S. macroptera both accumulated N in the absence of termites, but S. macroptera lost it when termites were present. The C/N ratio decreased with and without termites as decay proceeded in both species. Neobalanocarpus heimii accumulated P, but S. macroptera lost it with and without termites. The C/P ratio decreased in N. heimii, but did not change in S. macroptera. Decomposition was considerably enhanced by termites in S. macroptera, but not in N. heimii, indicating that termite foraging activity was affected by the different wood qualities of the two trees. The qualities responsible for the differences and how different wood qualities affect nutrient cycling in the tropical rain forest ecosystem are discussed.

We studied the resource allocation process of a large-seeded species, Dryobalanops lanceolata, during germination and early stages of seedling growth in Sarawak, East Malaysia. The seeds contained high contents of starch (74.3% of the total 1.57 g mean dry weight of the cotyledon) and lipid (15.0%). All of these reserves were exhausted by the time the first two pairs of leaves had developed (about 40 d after planting), but relatively little had been reserved in leaf or root by that time. This suggests that the large amount of seed reserve of D. lanceolata is necessary just to form a certain size of stem and the necessary number of leaves to set the plant up for photosynthesis. After seed reserves were exhausted, shoot elongation and new leaf production stopped, and most photosynthate was allocated to the expansion of the root system and to storage in the root as starch. The storage reserves in the root are thought to be used for the next growing stage, not to act as insurance for sprouting in case of shoot damage.

Geometroid moth abundance, species richness, weather and plant phenology were monitored monthly for 3 y in the lowland dipterocarp forest at Pasoh Forest Reserve, Negeri Sembilan in Malaysia. The intensity of tree flowering in the previous month (with mass events triggered in response to El Niño Southern Oscillations) was an important environmental factor positively correlated with the numbers of species and individuals of geometroid moths that emerge in any month. Abundance for geometroid moths was greater in months with high flowering and flushing in the previous month but low flowering in the month before that. Important weather parameters that influenced moth abundance were monthly rainfall, relative humidity and minimum temperature in previous months. High rainfall 3 mo previously led to an increase in moth abundance (perhaps by stimulating an increase in fresh plant material), whereas high rainfall and relative humidity thereafter served to decrease abundance, possibly by encouraging the spread and activity of pathogens: all these factors impacted on early life-stage survivorship. Similar trends were observed for individual geometroid families and subfamilies. The diversity measurement for the geometroid moths, α from the log-series, was correlated more with weather parameters than with tree phenology.

In a 30-ha permanent plot of tropical evergreen forest at Varagalaiar, Indian Western Ghats, all trees ≥ 30 cm girth at breast height (gbh) were examined for the presence of lianas ≥ 1 cm dbh. The plot contained 13 445 trees in 152 species and 11 200 lianas in 75 species. Twenty-eight per cent of trees supported lianas and the mean number of lianas per tree was 0.38 ± 0.72. Association analysis between lianas and trees of 16 tree families and 20 abundant tree species indicated that tree susceptibility to lianas was better pronounced at species rather than at family level. Overall, at Varagalaiar site, the aggregation of lianas followed neither Poisson nor clumped distribution. Among the four dominant tree families Dipterocarpaceae and Clusiaceae fit to the negative binomial model better than Euphorbiaceae and Meliaceae. These four families differed in their susceptibility level with 34.6% , 36.7% , 24.1% and 27.7% of trees ≥ 30 cm gbh respectively supporting lianas. At the species level, the proportion of trees with lianas was positively correlated with the mean branch free bole height of trees ≥ 30-40 and ≥ 40 cm gbh classes, and the mean number of lianas per tree was also positively correlated with the mean branch bole height of trees ≥ 30 cm gbh. Of the 16 abundant families, Euphorbiaceae contributed 31% and dominated the lower canopy, but its susceptibility to lianas was lower when compared to most other families.

This study compares leaf anatomy, chlorophyll content and photosynthetic induction rates for seedlings of five dipterocarp species growing both by a path and in the understorey of a Bornean heath forest. Hemispherical photographs were used to estimate the light level. Although three of the five species showed significantly higher photosynthetic capacity in high light conditions, there were no significant within-species differences in induction rates. Average induction times to reach 50% (T50%) and 90% (T90%) of maximum photosynthetic rate (Amax) were about 1.5 and 9 min for Shorea pachyphylla. In contrast, these were 18 and 37 min respectively for Dipterocarpus borneensis, and 12 and 25 min for Shorea multiflora. Intermediate values were recorded for Hopea pentanervia and Cotylelobium burckii. There was an overall weak and negative correlation of induction rate with stomatal density. Three species showed more rapid induction loss in their leaves from the path edge vs. the understorey. The results suggest that photosynthetic acclimation can influence some aspects of a leaf's dynamic response to sunflecks, such as Amax and induction loss, while not affecting overall induction rates. This study also shows significant differences among diptero carp species in photosynthetic capacity, induction responses and leaf structure, and in acclimation on these traits.

Leaf defences, leaf nutritional quality and leaf expansion rates may vary with resource availabilities to plants. Such variation could affect rates of leaf loss to herbivores, particularly along the steep resource gradients in disturbed forests. Intraspecific and interspecific variation in leaf damage and leaf expansion rates were measured on dipterocarp seedlings planted into secondary forests 1, 5 and 15 y after logging, and in adjacent primary forest of Sabah, Malaysia. Herbivory rates or amounts of leaf damage were compared across habitats and species for expanding, recently expanded, and mature leaves of Shorea leprosula and Dryobalanops lanceolata (Dipterocarpaceae). In all four habitats, leaves of the faster growing S. leprosula sustained higher rates and amounts of leaf-area loss than did the tougher leaves of slower growing D. lanceolata. Expanding leaves accumulated more leaf-area loss per week than did mature leaves. In all habitats and in both species, more than 25% of expanding leaves disappeared entirely. Rates of leaf-area loss per week differed among habitats for expanding leaves but not for mature leaves. In a relatively open, 1-y-old logged forest, faster leaf expansion reduced the time leaves spent in the most vulnerable stage; however, in S. leprosula a greater rate of leaf area loss countered the shorter expansion time. Thus, leaves accumulated similar total damages across habitats, and herbivory did not produce differences among habitats in seedling growth or mortality. High levels of resources may increase both leaf palatability and leaf expansion rates, with counteracting effects on herbivory.

Two contrasting forest formations (sensu Whitmore 1984), heath forest (HF) of a range of stature and tall lowland evergreen rain forest (LERF) occur frequently in close proximity in Borneo (Brtinig 1974). The two forest formations differ in floristic composition, stature and structure with the LERF being taller with emergent trees. One hypothesis to explain the striking differences between the two forest formations has been that the podsolized sandy soils of the HF (the LERF occurs on ultisols) together with the irregularly recurring periods of drought impose certain adaptation constraints on the component species of the HF (Richards 1996). Xeromorphic features such as small leaf size, high specific leaf weight and even canopy structure have been proposed by Brtinig (1974) as adaptive characters. The evidence presented so far to support the 'drought hypothesis' has been circumstantial (e.g. Becker & Wong 1993) and Proctor (1999) has argued that the main cause of HF is hydrogen ion toxicity in the very acid soils. Stomatal limitation of photosynthesis by drought is expected to result in higher than normal uptake of the heavier '3C isotope caused by decreased discrimination during drought (Farquhar et al. 1982). Therefore, isotopic signatures which integrate responses over the life-time of a leaf can be used to study the history of stomatal limitation. This paper describes the findings of a comparative study of the 8'3C signatures of some component species from a stand of short HF (c. 9 m tall) and tall LERF (c. 35 m). The study was carried out near the Barito Ulu Base Camp (1 14?01'E

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.

Long-term data on flower and fruit production of the forest community in two lowland tropical rain forests in north-western Sumatra are presented. The proportion of years with mast fruiting was found to be similar to that found elsewhere in Malesia. However, masting at the two sites, 70 km apart, did not coincide, and showed no correlation with the El Niño–Southern Oscillation phenomenon (ENSO). Comparisons with other sites in Malesia suggest a general waning of ENSO's impact toward western Malesia. Spatial variation at various scales in the timing of masting events was noted in Sumatra and elsewhere. This suggests that additional factors to ENSO play a role in determining forest-level mast fruiting, and we hypothesize that frugivorous animals have the opportunity to track mast fruiting. It is hypothesized that asynchrony between nearby areas in masting increases toward the western edge of Malesia.

The impact of the unusually severe drought associated with the 1997–1998 El Niño on tropical forest dynamics in Sarawak, Malaysia was examined. Mortality during the non-drought period (1993–1997) in a core plot (1.38 ha) was 0.89 % y−1, while that during the drought period (1997–1998) in the same plot and a peripheral plot was 6.37 and 4.35 % y−1, respectively. The basal area lost in the drought interval was 3.4 times that of the annual incremental basal area in 1993–1997. Drought mortality was higher for the smaller trees, though it was less size dependent than the non-drought mortality. Dipterocarpaceae, which is the dominant family in the study plot, had a mortality 12–30 times higher in the drought than the non-drought period. There were no significant differences in mortality among the topographic types. From the results of a log-linear model (multi-factored contingency table), the death of trees was correlated with size class, indicating a change in the size-class structure of the forest. Thus, both the species composition and structure are totally affected by such an episodic drought even in a per-humid tropical forest.

Leaf water and osmotic potentials and gas exchange were monitoredduring a prolonged El Nin˜o drought in 1998 for saplings of seven species in aBornean heath forest and compared with measurements taken during a sub-sequent wet period. The four dipterocarp species maintained reasonably goodwater status throughout the drought, especially Dipterocarpus borneensis which hadthick and deep tap roots. In contrast, two of three non-dipterocarp species, Cleis-tanthus baramicus and Tristaniopsis obovata displayed predawn leaf water potentialsapproaching their turgor-loss points. During the drought, all species except D.borneensis displayed strongly reduced stomatal conductance after a brief exposureto sun, and all displayed lower maximum rates of stomatal conductance and netphotosynthesis than during the wet period. Only Cotylelobium burckii displayed signi-ficant osmotic acclimation to the drought. T. obovata possessing a superficial rootsystem suffered a high mortality due to the drought, but recovered faster after thefirst rains than the other species all of which had tap roots. Deep roots and strongstomatal control favour trees in tropical heath forests where water deficits prob-ably occur regularly.KEY WORDS: dipterocarps, drought tolerance, El Nin˜o drought, haze, leaf waterpotential, osmotic potential, photosynthesis, root architecture, stomatal conduct-ance, tropical heath forest

Mast-fruiting is the intermittent and synchronous production of large fruits by a population of plants at long intervals (Herrera et al. 1998, Kelly 1994). Several hypotheses have been proposed concerning the adaptive advantages of mast-fruiting (Janzen 1971, 1974; Kelly 1994), and some field observations have provided evidence for these hypotheses (Norton & Kelly 1988, Shibata et al. 1998, Sork 1993). The predator-satiation hypothesis is one well-known explanation for reproductive synchrony in plants and animals (Janzen 1971, 1974; Kelly 1994). This hypothesis claims that mast fruiting at irregular intervals of several years is an effective means of satiating vertebrate fruit predators: low seed production can only support low densities of predators during the periods between mast-fruiting events, but more fruits are produced than predators can consume in masting years (Janzen 1971, Kelly 1994). Thus, it may be said that mast-fruiting is a defence strategy of plants against post-dispersal vertebrate fruit predators.

The mechanism of general flowering in Dipterocarpaceae in the Malay Peninsula is revealed through field survey and meteorological data analyses. The regions of general flowering coincide with those which experienced a low night-time temperature (LNT) c. 2 mo before flowering. This supports the hypothesis that low air temperature induces the development of floral buds of dipterocarps. LNT was found to be caused by radiative cooling during dry spells in winter when the northern subtropical ridge (STR) occasionally migrates southwards with a dry air mass into the equatorial region. LNT events usually occur in La Niña episodes, not in El Niño episodes as believed previously. This is because the southward migration of the STR is associated with the intensification of local meridional Hadley Circulation in the western Pacific, which is strengthened in a La Niña episode. Results suggest that El Niño-like climate change in increased atmospheric carbon dioxide concentrations may be critical for the tropical rain forest biome in south-east Asia.

Bears (Ursidae) are well known consumers of fruits and play an important role as seed dispersers in temperate forests (Welch et al. 1997, Willson 1993 and references therein). For tropical forest-dwelling bear species, however, very little information is known about frugivory and seed dispersal (Young 1990). The sun bear Helarctos malayanus is the smallest of the living bears, weighing from 24 to 65 kg (Ward & Kynaston 1995) and occurring throughout most of South-east Asia (Payne et al. 1985, Ward & Kynaston 1995). Their diet is described as bees nests (honey), termites, small animals and fruits (Payne et al. 1985). Ridley (1930) suggested that sun bears can disperse seeds of durians (Durio zibethinus, Bombacaceae), but nothing else had been reported on their role as seed dispersers. Here we report observations on the frugivory and seed dispersal by the sun bear in Central Kalimantan, Indonesia. The observations were carried out at the Barito Ulu Research Area (hereafter Rekut Camp), a 430-ha forest located in Central Kalimantan, Indonesia, at the confluence of the Rekut and Busang Rivers (113°56′E, 0.6°S). The vegetation is tropical hill evergreen rain forest with a dominance of Dipterocarpaceae (Whitmore 1984). The soils are acidic and low in nutrients

Performance of seedlings of seven rain forest, canopy dominant Shorea species was studied in a transplant experiment in forest sites at three different elevations (low, mid and high) within the humid zone of southwest Sri Lanka. Five species generally inhabit low- to mid-elevations, one at mid- and lower montane elevations, and one exclusively at lower montane elevations. Temperature, rainfall and cloudiness varied with elevation. For each site seedlings were grown in pots under partial shade conditions using similar soils and evermoist conditions. All growth measures showed differences among elevation sites, among species and in the interaction between species and elevation sites. Performances of species collectively showed (i) decline in height and leaf number with increase in elevation, (ii) higher dry mass at low- and mid-elevation sites compared to that at high-elevation and (iii) a higher mass of single leaves at the mid-elevation site than at the high-elevation site. Rank order of species changed across elevations for both height and dry mass. Dry mass declined with elevation in four of the seven species studied. S. gardneri, the only exclusively lower montane species, increased dry mass with elevation. Height declined with elevation for six of the species with only S. gardneri showing no change. Changes with elevation in the rank order of species for total leaf number and mass of single leaves were small. However, total leaf number and masses of single leaves differed among species and among elevations. S. megistophylla and S. disticha had a few leaves with high individual masses, while S. gardneri, S. affinis and S. trapezifolia had many leaves with less mass per individual leaf. One group of species showed relatively little change in leaf number per seedling and large changes in mass of single leaves. The other group varied more in leaf number but mass of individual leaves remained constant. Growth allocation to leaf production versus individual leaf size appears related to the successional division of Shorea section Doona. Also all species grew better at the low-elevation site irrespective of their natural ranges except S. gardneri, whose natural range is restricted to high elevations, and exhibits markedly lower growth responsiveness than the other wide ranging species.

Mycorrhizae, symbioses between plant roots and fungi, are found in virtually all terrestrial plant ecosystems. Substantial evidence indicates that mycorrhizal associations are beneficial to both partners. In most systems, the fungus benefits the host plant by effectively scavenging nutrients and in return, utilizes carbohydrates produced by the plant (Allen 1991, Harley & Smith 1983). Moreover, both major types of mycorrhizae, vesicular-arbuscular mycorrhizae (VAM) and ectomycorrhizae (EM), can alter the outcome of competitive interactions between host plants (Allen & Allen 1984, Hartnett et al. 1993, Hetrick et al. 1989, Newman et al. 1992, Perry et al. 1989). Early studies focused primarily on temperate mycorrhizae, but more recently, ecologists have turned toward the tropics. In contrast to the temperate zone, where trees tend to be EM, the majority of tropical tree species surveyed thus far form VAM (Janos 1983). Some notable exceptions of tropical trees forming EM occur in the plant families Dipterocarpaceae, Caesalpiniaceae, Euphorbiaceae, Fagaceae and Myrtaceae. Although tropical forests are typically diverse, many tree species in these five families grow in persistent, monodominant stands which can extend for hundreds of hectares (Connell & Lowman 1989). Janos (1983, 1985) has suggested that under low nutrient or seasonal conditions, EM may be more efficient than VAM at scavenging nutrients. Furthermore, EM may be able to absorb organic nitrogen (Alexander 1983), decompose organic litter (Trojanowski et al. 1984) and/or protect the host's roots from herbivory or pathogen attack (Marx 1972). Hence, the ability of some tropical trees to associate with EM has been hypothesized to give them a competitive advantage by which they can achieve local or regional dominance

Bukit Belalong, Brunei, is a small mountain (913 m) of uniform shale lithology with continuous primary rain forest from its base to its summit. Three 0.25 ha plots were established at each of three altitudes (200, 500 and 850 m) to investigate the altitudinal zonation of the soils and the vegetation. One soil profile from each altitude is described and chemical analyses of the soils indicate that they are similar at all altitudes. In each plot all trees ≥10 cm dbh were measured and identified as far as possible. Maximum tree height was greatest at 200 m (60 m) and least at 850 m (33 m). Tree density (number of individuals ha−1) increased with altitude. The forest at 850 m was the most species- and family-rich, but since the ratio of species to individuals did not vary significantly among altitudes, the higher species richness is attributed partly to the larger number of trees sampled. The Dipterocarpaceae was the most important family in terms of basal area at all altitudes, but its proportion of basal area was much smaller at 850 m than at the other altitudes. The Dipterocarpaceae was the most diverse family at 200 m and 500 m, but at 850 m its diversity was exceeded by the Lauraceae, Myrtaceae and Euphorbiaceae and equalled by the Clusiaceae. The forests at 200 m and 500 m are classified as lowland rain forest and that at 850 m is classified as a lower montane forest.

The growth habits of five species of hemiepiphytic fig trees (Ficus subgenus Urostigma) were compared to see if any species occupied distinct canopy positions or showed unique host preferences in lowland rain forest in Gunung Palung National Park, Indonesian Borneo. Highly significant differences among species were found in the height of establishment on hosts, the level at which fig crowns were deployed, and the size and taxa of host trees. Ficus stupenda, F. dubia, and F. subtecta all had mean establishment heights between 29 and 31m above the ground, had their crowns in the upper canopy, and predominantly occupied large trees in the Dipterocarpaceae. F. consociata and F. xylophylla established at significantly lower mean heights of 24 and 18 m respectively, had their crowns predominantly in lower canopy layers, and disproportionately occupied smaller non-dipterocarp trees. These patterns were consistent both within lowland forest on alluvial terraces, which was most intensively sampled, and when data were combined from three other contiguous lowland forest habitats. Ficus species appear to be specialized to some extent for distinct microhabitats within the canopy.

The relationship between sepal and nut size of fruits was studied in fruit of 394 species of Dipterocarpaceae in Malesia and Sri Lanka. The fruits of many dipterocarps have long twisted sepals which have a role as blades for dispersal by gyration. But long sepals decrease resource allocation to other parts, and increase the chance of fruit being trapped in the canopy. The frequency distribution of the ratio of sepal length to nut length was bimodal. The gyrationdispersed group with longer sepals comprised 74% of Dipterocarpaceae studied. The group with short sepal mainly comprised understorey trees, but there were a few emergents. In both groups, sepal areas were expressed as a power function of nut volumes'. Because fruit weight per sepal area increases with fruit size, larger fruits fall more quickly than smaller fruits, and sepals of the former can not serve so effectively as propeller blades. This is consistent with the fact that a few emergent trees with large nuts have short sepals and are not dispersed by gyration. Therefore, the re-evolution of short fruit sepals appears to have been mainly due to two reasons: reduction of tree height and enlargement of nut size.

The severe drought in 1982-1983 in south-east Asia caused wildfires in large areas of Borneo (Malingreau et al. 1985, Riswan & Yusuf 1986). In Sabah, Beaman et al. (1985) estimated that about 1 million ha of forest burned. Woods (1989) found that tree mortality after drought and fire was on average 2.5 times greater than that caused by drought alone and that mortality generally was higher in logged forests than in unlogged ones. He reported that the combined effect of drought and fire caused between 38 and 72% mortality in a forest selectively logged two years earlier. For saplings, the mortality on burnt plots exceeded 78% on all sites (Woods 1989). This paper describes the secondary vegetation after the 'Borneo fire' in a lowland rainforest area. Immediately after the fire it was almost devoid of green plants, except for a few surviving large trees which were more or less damaged. The area of 18.7 ha is located at an elevation of 650-750 m asl, c. 35 km south-east of Sipitang (1 150 5' E, 50 0' N) in the south-western part of Sabah. The soil type is an haplic acrisol on a bedrock consisting of mudstones, sandstones and carboniferous shales. The annual rainfall for the years 1985-1990 averaged 3352 mm (Malmer 1992). The vegetation before the Borneo fire was a lowland dipterocarp forest which was lightly selectively logged in 1981. In an adjacent area which was not burnt the number of trees per ha with dbh >20 cm was 145 and the volume 146 m3 ha-' (Sim & Nykvist 1991). The six most abundant families in terms of tree volume were Dipterocarpaceae, Lauraceae, Legumninosae, Sterculiaceae, Myrtaceae and Euphorbiaceae (Sim & Nykvist 1991). The distance between

A permanent plot of 28 ha was established in a dense wet evergreen forest in the Western Ghats of India to study the functioning of the ecosystem. Since April 1990, 1981 trees of ≥30 cm gbh have been enumerated in a systematic sampling of five strips totalling 3.12 ha. This paper describes the main structural and floristic characteristics of the plot.The density (635 trees ≥30 cm gbh per hectare) and basal area (39.7 m2 ha−1) are high. Despite the high diversity (Simpson's D = 0.92 and Shannon's H' = 4.56), four species are distinctly, dominant in terms of an importance value index (relative density + relative basal area). Each of these four species occupies a different layer in the ecosystem: Humboldtia brunonis Wall. (Fabaceae) dominates the undergrowth, Myristica dactyloïdes Gaertn. (Myristicaceae) the intermediate strata, Valeria indica L. (Dipterocarpaceae) the higher canopy level and Dipterocarpus indicus Bedd. (Dipterocarpaceae) the emergents. This pronounced species hierarchy is one of the most important characteristics of the evergreen forests of the Western Ghats. The two dipterocarps account for 20.1% of the total number of trees and contribute 40.9% to the total basal area. This formation can, therefore, be considered as the westernmost lowland dipterocarp forest of Asia.Analysis of the spatial variations in the floristic composition and in the structure of the main species populations shows that two kinds of mature phases can be identified: where the topography is raised and gently sloping, the vertical structure of the stand is discontinuous, with Dipterocarpus indicus and Vateria indica forming an emergent layer above a dense undergrowth; on slopes, the stand is lower, vertically continuous and saturated with Valeria indica and Myristica dactyloïdes. The link between the structure of the stand and dynamic processes is discussed.

Selective logging is the predominant method of commercial timber exploitation in South East Asia. Its effects upon mammalian carnivores have seldom been addressed, despite the vulnerability of these animals at the top of many food chains. The authors investigated the effects of logging by comparing the abundance of sympatric civet species, which display feeding strategies ranging from strict carnivory tofrugivory, in primary and selectively logged rainforest in the Malaysian state ofSabah in northern Borneo. All species occurred in disturbed forest, but the overall density of civets in logged forest (6.4 individuals per sq km) was found to be significantly lower than in primary forest (31.5 individuals per sq km). This reflected a marked reduction in the abundance of civets from the predominantly carnivorous subfamilies Viverrinae and Hemigalinae.

Many rain-forest trees in South-East Asia, including the dominant canopy family Dipterocarpaceae, reproduce in gregarious mast-fruiting events once every 2-11 y (Ashton et al. 1988). The dominant hypothesis for the evolution of masting is that predators are incapable of consuming mast seed crops, so that natural selection has favoured parent trees that fruit in synchrony (Janzen 1974, 1976). Mast flowering and fruiting are visually spectacular and quantified in harvest records for dipterocarp species producing large, oil-rich tengkawang seeds (Curran et al. 1999). Seedling recruitment following a mast is less obvious and has no immediate commercial value. However, a number of pulses of recruitment have been documented (Ashton et al. 1988, Chan 1980, Fox 1972, Liew & Wong 1973). These, together with general acceptance of the satiation hypothesis, have led to the widespread assumption that masts reliably increase seedling density and generate distinct seedling cohorts (Whitmore 1998). Indeed, foresters in Malaysia and Indonesia often recommend harvesting only after a mast, to ensure high densities of seedling regeneration. But evidence from Indonesian Borneo suggests that human activities may be disrupting predation during masts (Curran et al. 1999). Logging and forest fragmentation appear to have intensified the activities of nomadic, vertebrate seed predators in the remaining patches of primary forest. It remains possible, however, that even a small fraction of seeds escaping seed predation could survive well after germination and contribute substantially to recruitment. In a study of the effects of density dependence on the dynamics of dipterocarp regeneration, we measured seedling recruitment per capita adult in a common canopy species (Shorea quadrinervis Sloot.). The density of seedlings (< 25 cm

Seeds of Dryobalanops aromatica and D. lanceolata (Dipterocarpaceae) were sown in gaps and understorey on a ridge and a valley in a Bornean rainforest. Germination rates were 92–100% regardless of site and species. On the ridge, the proportion of seedlings that opened primary leaves was larger in D. aromatica (19–30%) than in D. lanceolata (7–19%) due to higher root predation on D. lanceolata. In the valley, on the other hand, the proportion was larger in D. lanceolata (71–74%) than in D. aromatica (56%). After primary leaf production, seedlings of both species had higher survivorship in the gaps than in the understorey. Interactions between predators, soil conditions and light environment and their effects on seedling establishment are discussed.

Effects of tree species heterogeneity on leaf fall were studied in a primary (4 ha) and in a selectively logged forest plot (2.5 ha) in the Ulu Segama Forest Reserve, Sabah, Malaysia, from April 1988 to December 1989. Leaf fall was collected at 30 sampling points in each plot, and identified to species.Dipterocarpaceae, Euphorbiaceae, Lauraceae, Fagaceae and Meliaceae are important tree families in both plots with regard to their contribution to total basal area, tree density and annual leaf fall. The total number of tree species was higher in the primary forest plot (267) than in the logged forest plot (218), although the number of climber species was higher in the logged forest (44) than in the primary forest plot (33). The overlap in species composition between the two forest plots was relatively small (49%) compared with that in family composition (88%).In the primary forest plot, the Dipterocarpaceae contributed 29% of the total basal area and 34% of the annual leaf fall. In the logged forest plot these contributions were much lower, 11% and 15%. The contribution to annual leaf fall made by climbers and pioneer trees was higher in the logged forest plot (34%) than in the primary forest plot (8%).In the primary forest plot, leaf fall was dominated My large emergent and main canopy trees, mainly dipterocarps, and occurred as regular large peaks. In the logged forest leaf fall was dominated by climbers and many, relatively small trees of pioneer species, such as Macaranga hypoleuca, and was more evenly distributed in time.

Numbers of lianas ≥2 cm gbh were recorded on trees ≥30 cm gbh in two 4 ha plots of dipterocarp forest. Associations between lianas and trees of the 12 commonest families and 16 commonest species were analysed. Liana density was 882 ha-1. Fifty-seven per cent of trees supported lianas and the mean number lianas per tree was 2.1. Lianas were highly aggregated on individual trees in most families; numbers of lianas per tree followed the negative binomial distribution for the Dipterocarpaceae but not Euphorbiaceae. Dipterocarpaceae and Euphorbiaceae differed in susceptibility, with 41 and 64% of their trees respectively supporting lianas. The proportions of trees with lianas (i.e. % trees laden) were correlated between plots at the species, but not the family, level. They were not related to tree girth; differences in proportions between families and species were maintained for trees in the 30–40 cm gbh class. At the species level, proportions of trees with lianas and the mean number of lianas per tree were significantly inversely correlated with mean branch-free bole height of trees in the 30–40 cm gbh class. Increased branch-free bole height and associated branch shedding may therefore decrease the susceptibility of trees to lianas and explain the lower susceptibility in the Dipterocarpaceae than the Euphorbiaceae.

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.

Nanophyes shoreae is a pre-dispersal fruit-predator of several species of Dipterocarpaceae. The timing of oviposition of this weevil was monitored in six trees in Pasoh Forest Reserve, West Malaysia from September 1986 to February 1987. A flowering event occurred during this period. Oviposition started within 12 days after peak anthesis, and continued within any one tree for 11–39 days. Host trees of N. shoreae flowered over a 75 day period. Intra-specific flowering synchrony was high but different species flowered sequentially. The behaviour of N. shoreae and the period of the oviposition ‘window’ strongly suggest that this pre-dispersal fruit-predator ‘tracks’ the sequence of flowering shown by its host species. The implications for predator satiation through mass-flowering of the Dipterocarpaceae are discussed.

There was fruiting of the dipterocarps of Pantai Aceh Forest Reserve, Penang, Peninsular Malaysia in September 1986. The opportunity was taken to investigate the establishment and seedling survival of Shorea curtisii, Shorea multiflora and Shorea pauciflora over the subsequent year. The germination and seedling survival of Shorea curtisii was compared between canopy gaps and forest understorey sites.Under the shaded conditions none of the species grew beyond the two leaf stage over their first year. Shorea multiflora seedlings suffered a 72% mortality, significantly lower than that of Shorea pauciflora (89%) and Shorea curtisii (93%). The major cause of mortality appeared to be drought, though Shorea curtisii was also prone to predation by small mammals.In a gap, Shorea curtisii seeds probably germinated less well but seedling survival (28% versus 7%) and growth was better than canopy-shaded conspecifics. Seedlings in gaps escaped small mammal predation.