Dipterocarp Trees Research Articles

Amber fossils reveal the Early Cenozoic dipterocarp rainforest in central Tibet

The palaeoenvironmental reconstruction of central Tibet is key to understanding the uplift history of the Tibetan Plateau, which had a profound influence on Cenozoic global climate and biotic change. Here we report an amber layer from the lower part of the Dingqing Formation (late Oligocene) in Lunpola of central Tibet, which is the first record of amber from Tibet. Herein we find that Lunpola amber is derived from dipterocarp trees, as determined by gas chromatography-mass spectrometry, which are restricted to and dominant in Asian rainforest nowadays. This amber forest represents the northernmost dipterocarp forest and is consistent with the hypothesis of out-of-India dispersal of Asian dipterocarps. The Lunpola amber most probably was derived from the lower part of the Niubao Formation (early–middle Eocene) and suggests a tropical/subtropical wet forest was present in central Tibet at least before the late Oligocene (probably early–middle Eocene).

Inter-annual dynamics and persistence of small mammal communities in a selectively logged tropical forest in Borneo

Understanding temporal change and long-term persistence of species and communities is vital if we are to accurately assess the relative values of human-modified habitats for biodiversity. Despite a large literature and emerging consensus demonstrating a high conservation value of selectively logged tropical rainforests, few studies have taken a long-term perspective. We resampled small mammals (≤ 1 kg) in a heavily logged landscape in Sabah, Borneo between 2011 and 2016 to investigate temporal patterns of species-level changes in population density. We found that small mammal population density in heavily logged forest was highly variable among years, consistent with patterns previously observed in unlogged forest, and uncovered evidence suggesting that one species is potentially declining towards local extinction. Across nine species, population densities varied almost sevenfold during our 6-year study period, highlighting the extremely dynamic nature of small mammal communities in this ecosystem. Strictly terrestrial murid species tended to exhibit strong temporal dynamics, whereas semi-arboreal foraging species such as treeshrews had more stable dynamics. We found no relationships between population density and fruit/seed mass, and therefore no evidence that our patterns represent responses to inter-annual mast fruiting of the dominant canopy dipterocarp trees. This may be due to the removal of most of the canopy during logging, and hence the dipterocarp seed resource, although it possibly also reflects spatiotemporal limitations of our data. Our results underline the importance of understanding long-term variability in animal communities before developing conservation and management recommendations for human-altered ecosystems.

Differences in the fruit maturation stages at which oviposition occurs among insect seed predators feeding on the fruits of five dipterocarp tree species

The seeds of dipterocarp trees are the main food resources for many species of weevils, bark beetles and small moths; however, for most seed-eating insects on dipterocarp tropical trees, seed utilization patterns remain poorly investigated. This study aimed to determine the fruit maturation stages at which eggs are laid by different insect seed predators feeding on the seeds or fruits of the following five dipterocarp species: Dipterocarpus globosus, Dryobalanops aromatica, Shorea beccariana, S. acuta and S. curtisii, which reproduced during the same period. We investigated the occurrence frequencies of the insect seed predators at various growth stages by collecting both unfallen and fallen fruit on several occasions during the period of seed/fruit maturation in a tropical rainforest in Borneo from September to December 2013. Weevils and bark beetles were the dominant insect seed predators of the five tree species. One or two weevil species of Alcidodes, Damnux and/or Nanophyes preyed on the seeds of each of the five tree species, and one bark beetle species, Coccotrypes gedeanus, preyed on the seeds of all five tree species. Many larvae, pupae and adults of each weevil species were found in pre-dispersal (unfallen) fruit, whereas bark beetles at various growth stages were found in post-dispersal (fallen) fruit. These results suggested that, among the dominant insect seed predators of the five dipterocarp species, weevil species oviposit on pre-dispersal fruit and begin their larval growth before seed dispersal, whereas the oviposition and larval development of bark beetle species occurs in post-dispersal fruit.

Financial analysis of dipterocarp log production and rubber production in the forest and land rehabilitation program of Sekolaq Muliaq, West Kutai District, Indonesia

Lahjie AM, Lepong A, Simarangkir BDAS, Kristiningrum R, Ruslim Y. 2018. Financial analysis of dipterocarp log production and rubber production in the forest and land rehabilitation program of Sekolaq Muliaq, West Kutai District, Indonesia. Biodiversitas 19: 757-766. The Dayak community of East Kalimantan in the last decade has begun to develop production systems that integrate forest timber tree species into plantation commodity enterprises. They have become aware that the natural forest species of their surroundings such as Meranti (Shorea sp.) and Kapur (Dryobalanops aromatica) are often easier to exploit economically, and represent potentially cheaper investments, than are introduced plantation crops such as rubber (Hevea brasiliensis). This is because the price of rubber latex has decreased over the years and has ceased to give a financial return commensurate with the investment required to develop rubber as a monocrop. The research described in this paper aimed to evaluate the viability of a dipterocarp forest/rubber plantation system cultivated by people in the West Kutai District of East Kalimantan. The viability of the system was evaluated by (i) measuring its production of dipterocarp logs and natural rubber; (ii) determining the diameter distribution of its dipterocarp trees and (iii) assessing the financial feasibility of the dipterocarp/rubber system using the theories of increment production and basal area applied to the determination of Pay Back Period, Net Present Value (NPV), Net Benefit Cost (B/C) ratio and Internal Rate of Return (IRR). The research areas on which the evaluation was performed consisted of (1) a mixed population of Shorea spp. (Meranti) and rubber (Hevea brasiliensis) and (2) a mixed population of Dryobalanops aromatica (Kapur) and rubber. The growth analysis of Shorea spp. combined with rubber as well as D. aromatica combined with rubber at the planting distance of 5m x 5m showed that the maximum cycle was reached at the age of 40 years. Whereas the rubber trees in monoculture cultivation reached their maximum cycle at the age of 17 years. The optimum increment of MAI and CAI of Shorea spp. combined with rubber reached 3.61 m3 ha-1 year-1 and 3.62 m3 ha-1 year-1 respectively. The maximum increment of MAI and CAI of Dryobalanops aromatica combined with rubber reached 3.09 m3 ha-1 year-1 and 3 m3 ha-1 year-1 respectively.

<b>Notes on the taxonomy and distribution of two endemic and threatened dipterocarp trees from the Western Ghats of Kerala, India</b>

Hopea glabra Wight & Arn. and Hopea utilis (Bedd.) Bole are two little-known highly threatened endemic dipterocarps distributed in evergreen forests of the Western Ghats. Although literature surveys and herbarium records show occurrence of these species in different forest areas of Kerala, the present study could locate Hopea glabra from the Silent Valley National Park and Hopea utilis from Shankili forests in Kulathupuza range, enabling the portrayal of current distribution, basic ecology covering phenology, species association, regeneration and conservation status along with taxonomic notes.

Plant\u2013soil interactions maintain biodiversity and functions of tropical forest ecosystems

Tropical forests are characterized by high biodiversity and aboveground biomass growing on strongly weathered soils. However, the distribution of plant species and soils are highly variable even within a tropical region. This paper reviews existing and novel knowledge on soil genesis, plant and microbial physiology, and biogeochemistry. Typically, forests in Southeast Asia are dominated by dipterocarps growing on acidic Ultisols from relatively young parent material. In the Neotropics and Africa, forests contain abundant legume trees growing on Oxisols developed in the older parent materials on stable continental shields. In Southeast Asia, the removal of base cations from the surface soil due to leaching and uptake by dipterocarp trees result in intensive acidification and accumulation of exchangeable Al3+, which is toxic to most plants. Nutrient mining by ectomycorrhizal fungi and efficient allocation within tree organs can supply phosphorus (P) for reproduction (e.g., mast fruiting) even on P-limited soils. In the Neotropics and Africa, nitrogen (N) fixation by legume trees can ameliorate N or P limitation but excess N can promote acidification through nitrification. Biological weathering [e.g., plant silicon (Si) cycling] and leaching can lead to loss of Si from soil. The resulting accumulation of Al and Fe oxides in Oxisols that can reduce P solubility through sorption and lead to limitation of P relative to N. Thus, geographical variation in geology and plant species drives patterns of soil weathering and niche differentiation at the global scale in tropical forests.

Defaunation and habitat disturbance interact synergistically to alter seedling recruitment

Vertebrate granivores destroy plant seeds, but whether animal-induced seed mortality alters plant recruitment varies with habitat context, seed traits, and among granivore species. An incomplete understanding of seed predation makes it difficult to predict how widespread extirpations of vertebrate granivores in tropical forests might affect tree communities, especially in the face of habitat disturbance. Many tropical forests are simultaneously affected by animal loss as well as habitat disturbance, but the consequences of each for forest regeneration are often studied separately or additively, and usually on a single plant demographic stage. The combined impacts of these threats could affect plant recruitment in ways that are not apparent when studied in isolation. We used wire cages to exclude large (elephants), medium, (sambar deer, bearded pigs, muntjac deer), and small (porcupines, chevrotains) ground-dwelling mammalian granivores and herbivores in logged and unlogged forests in Malaysian Borneo. We assessed the interaction between habitat disturbance (selective logging) and experimental defaunation on seed survival, germination, and seedling establishment in five dominant dipterocarp tree species spanning a 21-fold gradient in seed size. Granivore-induced seed mortality was consistently higher in logged forest. Germination of unpredated seeds was reduced in logged forest and in the absence of small to large-bodied mammals. Experimental defaunation increased germination and reduced seed removal but had little effect on seed survival. Seedling recruitment however, was more likely where logging and animal loss occurred together. The interacting effects of logging and hunting could therefore, actually increase seedling establishment, suggesting that the loss of mammals in disturbed forest could have important consequences for forest regeneration and composition.

Relative ranges of mating and dispersal modulate Allee thresholds in sessile species

Sessile organisms, including plants and benthic macrofauna, are often restricted in the ranges over which they are able to reproduce and disperse. This leads to spatial patterning within populations, causing the effective population density around each individual to depart from the average across its range. This has important implications for population dynamics, in particular the minimum density at which populations are able to maintain positive growth (the Allee threshold). Here we compare the population dynamics of species with three syndromes — spatially restricted mating, dispersal or both — against a null model of a species with no spatial limitations. First we demonstrate mathematically that the population density at which Allee effects occur systematically shifts in each case. Next we use individual-based models representing three exemplar species to simulate the implications for the Allee threshold of each within a fixed area. In the case where mating occurs over long ranges but dispersal is restricted (e.g. the wind-pollinated silver fir, Abies alba Mill.), there is a negligible impact on the Allee threshold. When mating is also spatially restricted (e.g. the dipterocarp tree Shorea curtisii Dyer ex King), the Allee threshold reduces, unless high death rates prevent the stabilisation of aggregations. This occurs because offspring remain within the range of potential mating partners. Finally we consider a case in which mating is short-ranged, and dispersal effectively unrestricted, but in which individuals choose to locate themselves in the vicinity of conspecifics (e.g. acorn barnacles, Semibalanus balanoides). This has the effect of maintaining clustering in the face of high dispersal, reducing the Allee threshold, and compensating for the apparent cost of short-range mating. Incorporating information on ranges of mating and dispersal can lead to more effective models for the management of populations at low density, in particular the identification of species with syndromes which make them vulnerable to Allee effects. Most notably, mechanisms which increase the degree of clustering in populations increase both their resilience and persistence when finding a mate is the greatest challenge faced by a sessile organism.

The impact of climate change on the distribution of two threatened Dipterocarp trees.

Two ecologically and economically important, and threatened Dipterocarp trees Sal (Shorea robusta) and Garjan (Dipterocarpus turbinatus) form mono‐specific canopies in dry deciduous, moist deciduous, evergreen, and semievergreen forests across South Asia and continental parts of Southeast Asia. They provide valuable timber and play an important role in the economy of many Asian countries. However, both Dipterocarp trees are threatened by continuing forest clearing, habitat alteration, and global climate change. While climatic regimes in the Asian tropics are changing, research on climate change‐driven shifts in the distribution of tropical Asian trees is limited. We applied a bioclimatic modeling approach to these two Dipterocarp trees Sal and Garjan. We used presence‐only records for the tree species, five bioclimatic variables, and selected two climatic scenarios (RCP4.5: an optimistic scenario and RCP8.5: a pessimistic scenario) and three global climate models (GCMs) to encompass the full range of variation in the models. We modeled climate space suitability for both species, projected to 2070, using a climate envelope modeling tool “MaxEnt” (the maximum entropy algorithm). Annual precipitation was the key bioclimatic variable in all GCMs for explaining the current and future distributions of Sal and Garjan (Sal: 49.97 ± 1.33; Garjan: 37.63 ± 1.19). Our models predict that suitable climate space for Sal will decline by 24% and 34% (the mean of the three GCMs) by 2070 under RCP4.5 and RCP8.5, respectively. In contrast, the consequences of imminent climate change appear less severe for Garjan, with a decline of 17% and 27% under RCP4.5 and RCP8.5, respectively. The findings of this study can be used to set conservation guidelines for Sal and Garjan by identifying vulnerable habitats in the region. In addition, the natural habitats of Sal and Garjan can be categorized as low to high risk under changing climates where artificial regeneration should be undertaken for forest restoration.

Changes in Leaf Characteristics with Tree Age in <i>Dryobalanops beccarii</i> Dyer in a Restored Forest of Sarawak, Malaysia

Study on leaf properties of an endangered dipterocarp tree species, Dryobalanops beccarii, was conducted in a restored forest. The study focused on the morphology, nutrient concentration and gas exchange in well-developed leaves of D. beccarii at different ontogenetic phases. The hypothesis tested that leaf physiological and morphological changes are related to the nutrient concentration level of D. beccarii leaves in each ontogenetic phase. Seedling leaves were small and thin, whereas adult tree leaves were the large and thick. The stomata density per unit was abundant in adult tree leaves as compared to seedlings and saplings leaves. The net photosynthetic rate (Pn), transpiration rate (A) and stomatal conductance (gs) was increased from the seedling phase until the sapling phase, but decreased as the D. beccarii reached the mature phase. Scarce stomata density in seedling leaves contributed to low Pn, A and gs, while sapling leaves recorded opposite results due to abundant stomata density accompanied by highest accumulation of nitrogen (N) content per unit leaf area. The low concentration of nitrogen (N), phosphorus (P) and magnesium (Mg) detracted the gas exchange performance. Hence, changes in leaf morphology and physiology of D. beccarii were affected by the differences in resource used at each tree ontogenetic phase.

The value of biodiversity for the functioning of tropical forests: insurance effects during the first decade of the Sabah biodiversity experiment.

One of the main environmental threats in the tropics is selective logging, which has degraded large areas of forest. In southeast Asia, enrichment planting with seedlings of the dominant group of dipterocarp tree species aims to accelerate restoration of forest structure and functioning. The role of tree diversity in forest restoration is still unclear, but the ‘insurance hypothesis’ predicts that in temporally and spatially varying environments planting mixtures may stabilize functioning owing to differences in species traits and ecologies. To test for potential insurance effects, we analyse the patterns of seedling mortality and growth in monoculture and mixture plots over the first decade of the Sabah biodiversity experiment. Our results reveal the species differences required for potential insurance effects including a trade-off in which species with denser wood have lower growth rates but higher survival. This trade-off was consistent over time during the first decade, but growth and mortality varied spatially across our 500 ha experiment with species responding to changing conditions in different ways. Overall, average survival rates were extreme in monocultures than mixtures consistent with a potential insurance effect in which monocultures of poorly surviving species risk recruitment failure, whereas monocultures of species with high survival have rates of self-thinning that are potentially wasteful when seedling stocks are limited. Longer-term monitoring as species interactions strengthen will be needed to more comprehensively test to what degree mixtures of species spread risk and use limited seedling stocks more efficiently to increase diversity and restore ecosystem structure and functioning.

Growth and survival of hybrid dipterocarp seedlings in a tropical rain forest fragment in Singapore

Background: Although natural hybridisation between dipterocarp trees is considered rare, putative dipterocarp hybrids (Shorea spp.) are found in a forest fragment in Singapore. Understanding the performance of hybrids is critical to inform conservation efforts and has implications for the demographic and genetic viability of these small populations.Aims: First, is there a difference in the frequency of hybrids between the mature and seedling stages, and second, do parent and hybrid seedlings have different ecological traits?Methods: We analysed seedling survival and growth rates in relation to environmental variables for Shorea curtisii, S. leprosula and hybrids of the two species. We monitored the height and diameter of seedlings for 4 years, as well as light conditions and soil moisture.Results: The proportion of hybrids at the seedling stage was 41% for S. leprosula and 17% for S. curtisii, respectively. Hybrids were more frequent at the seedling stage than at the mature stage. Hybrid individuals had growth and survival rates comparable to their parent species, with the exception of slower growth rates than S. leprosula.Conclusions: Hybrid seedlings lacked obvious heterosis, and might therefore have similar fitness to that of parent species in the present forest environment.

Allometric projections of time-related growth trajectories of two coexisting dipterocarp canopy species in India

Background: The Western Ghats of India contain the westernmost dipterocarp forests of Asia. However, only a few dipterocarp tree species actually coexist in the forest canopy among which Vateria indica and Dipterocarpus indicus are the most common. The mechanisms contributing to the coexistence of these phylogenetically closely related species have not been identified.Aims: We investigated the time-related growth trajectories in diameter, height and crown size of these two species in the Uppangala Permanent Sample Plot to determine if trade-offs in their three-dimensional developmental strategies could contribute to their long-term coexistence.Methods: From annual diameter growth data of 692 trees >9.55 cm in diameter at breast height over a 21-year period, we developed time-related diameter growth models for the two species, accounting for local density-dependent competition effects and topography. Combining the diameter growth models with static stem and crown allometries, we projected time-related tree growth trajectories in height and crown size.Results: While both species can reach similar dimensions, V. indica grows much faster, or at least as fast as D. indicus in diameter, height and crown size in all the observed situations. Both species respond similarly to topography, but V. indica appears to be more responsive to local density-dependent competition than D. indicus. Finally, V. indica shows higher mortality and recruitment rates and a greater basal area increase than D. indicus.Conclusions: These results refute our hypothesis that D. indicus coexists with the outperformer V. indica by a growth strategy allowing selected individuals in favourable conditions to reach the canopy more quickly than their competitors. The current coexistence of the two dipterocarp species at Uppangala appears not to be at a static equilibrium; V. indica probably being in a phase of canopy stand colonisation.

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.

Short Communication: The survival rate and one-year growth of Shorea javanica, Shorea macrobalanos and Hopea mengarawan in coal mined land in Central Bengkulu, Indonesia

Wiryono, Suhartoyo H, Munawar A. 2016. Short Communication: The survival rate and one-year growth of Shorea javanica, Shorea macrobalanos and Hopea mengarawan in coal mined land in Central Bengkulu, Indonesia. Biodiversitas 17: 741-745. Dipterocarp trees used to dominate the lowland forest of Sumatra and Kalimantan. Currently, however, dipterocarp trees are rare due to deforestation of natural forest. One major cause of deforestation in Sumatra and Kalimantan is coal mining. Rehabilitation of coal mined soil is usually done using fast-growing alien species. We tried to restore a piece of mined land in Central Bengkulu, using commercially valuable species of Dipterocarpaceae, namely Shorea javanica Koord. & Valet., Shorea macrobalanos Ashton and Hopea mengarawan Miq. In this article, we presented the survival rate and growth of the one year old seedlings of these three species within one year of observation. Of the three species, S. macrobalanos had the highest survival rate (93%), followed by S. javanica (80%) and H. mengarawan (77%). Within a year, the one year old seedlings of S. macrobalanos grew 452% in height, significantly higher than that of S. javanica (221%) and of H. mengarawan (119%). Shorea macrobalanos also had the highest growth in diameter within a year, namely 337%, followed by S. javanica (145%) and H. mengarawan (135%). It can be concluded that within a year of observation, the three species of dipterocarps could grow relatively well in mined land. It is therefore recommended that in the restoration of mined land in Sumatra economically valuable native species of dipterocarps should be used instead of fast-growing alien species.

Increased water use in dry season in eight dipterocarp species in a common plantation in the northern boundary of Asian tropics

AbstractThe seasonal water use and stand‐level transpiration of the important tropical timber tree family, Dipterocarpaceae, have not been well investigated. Here, we characterized the seasonal water use and stand‐level transpiration of eight, evergreen, dipterocarps in tropical Southwest China in the 2013 wet and dry seasons: six species grown in monoculture and two species in mixture. We estimated stand‐level transpiration using a power model, combining data from 22 trees of all species measured in the two seasons. Despite significant decreases in soil volumetric water content within 1‐m depth, predawn leaf water potentials (> −0.5 MPa) of all trees indicated access of roots to water. Daily sap flux density (SFDd) of all species closely responded to vapour pressure deficit (VPD). Dry season VPD increased by 29%, compared to in wet season, resulting 27–52% increased SFDd in six of the eight species. Whole tree daily water use was scaled with diameter at 1.3 m height for the 22 trees (r2 = 0.91 and 0.93 in the wet and dry seasons, respectively). Daily mean stand‐level transpiration ranged from 0.63 to 2.23 mm d−1 (mean = 1.05) and from 1.18 to 2.29 mm d−1 (mean = 1.63) in the wet and dry seasons, respectively. Our results reveal conservative water use of dipterocarps and increased transpiration in dry season when a stable soil water source is available. In comparison with introduced fast‐growing timber species, such as Eucalyptus and Acacia mangium, dipterocarp trees and forests consume much less water, making them more suitable as plantation timber crops for the region. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

Controlled release of borneol from nano-fibrous poly(L-lactic acid)/ cellulose acetate butyrate membrane

Borneol, one of the commonly used Chinese medicines, can be used to treat many diseases. The main ingredient of natural borneol is d-borneol extracted from the volatile oil of dipterocarp trees. Numerous studies have proved the effectiveness of borneol. It has been widely used in relieving symptoms of anxiety, fatigue and insomnia; inducing anaesthesia and analgesia to alleviate abdominal pain, wounds and burns; relieving rheumatic pain, hemorrhoids, skin diseases and ulcerations of the mouth, ears, eyes or nose; treating sore throats and skin infections; and is mainly used to treat cardiovascular and cerebrovascular diseases. Although borneol has a significant therapeutic effect, its easy sublimation and low water absorbability make it difficult to control the efficiency of delivery and decrease its function in connecting to various applications in the needs of modern society. Electrospun nanofiber has been commonly used as a delivery vehicle for various medicines for biomedical applications. Poly(L-lactic acid) and cellulose acetate butyrate (CAB) nano-fibrous nonwoven membranes were electrospun and used as drug carriers for borneol. To load borneol into a PLLA/CAB composite membrane, borneol/acetone solution was sprayed on PLLA/CAB fibers. While part of the CAB was dissolved by acetone, borneol was combined with CAB by hydrogen bonds between hydroxyl and carbanyl groups. PLLA still kept a porous morphology of the whole drug-loaded membrane since it does dissolve in acetone. This structure provided a high quality and stable drug delivery system. With adjustable drug release properties, PLLA/CAB nano-fibrous composite nonwoven membranes can be alternative candidates for developing novel external medical textiles.

Contrasting diversity and host association of ectomycorrhizal basidiomycetes versus root-associated ascomycetes in a dipterocarp rainforest.

Root-associated fungi, including ectomycorrhizal and root-endophytic fungi, are among the most diverse and important belowground plant symbionts in dipterocarp rainforests. Our study aimed to reveal the biodiversity, host association, and community structure of ectomycorrhizal Basidiomycota and root-associated Ascomycota (including root-endophytic Ascomycota) in a lowland dipterocarp rainforest in Southeast Asia. The host plant chloroplast ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit (rbcL) region and fungal internal transcribed spacer 2 (ITS2) region were sequenced using tag-encoded, massively parallel 454 pyrosequencing to identify host plant and root-associated fungal taxa in root samples. In total, 1245 ascomycetous and 127 putative ectomycorrhizal basidiomycetous taxa were detected from 442 root samples. The putative ectomycorrhizal Basidiomycota were likely to be associated with closely related dipterocarp taxa to greater or lesser extents, whereas host association patterns of the root-associated Ascomycota were much less distinct. The community structure of the putative ectomycorrhizal Basidiomycota was possibly more influenced by host genetic distances than was that of the root-associated Ascomycota. This study also indicated that in dipterocarp rainforests, root-associated Ascomycota were characterized by high biodiversity and indistinct host association patterns, whereas ectomycorrhizal Basidiomycota showed less biodiversity and a strong host phylogenetic preference for dipterocarp trees. Our findings lead to the working hypothesis that root-associated Ascomycota, which might be mainly represented by root-endophytic fungi, have biodiversity hotspots in the tropics, whereas biodiversity of ectomycorrhizal Basidiomycota increases with host genetic diversity.

Nutrient resorption is associated with leaf vein density and growth performance of dipterocarp tree species

Summary Nutrient resorption is important for the nutrient budget of plants, but little is known about which plant traits mediate nutrient resorption, how resorption efficiency is associated with other leaf traits and whether nutrient resorption has an impact on plant growth. In this study, 17 dipterocarp tree species were compared in a common garden experiment. N and P resorption efficiencies were regressed against suites of traits associated with phloem transport capacity (i.e. leaf vein density; Dvein), leaf nutrient conservation traits (e.g. leaf mass per area; LMA) and species growth rate. Across the dipterocarp species studied, N resorption efficiency (percentage N resorbed) was positively correlated with Dvein and leaf thickness. N resorption efficiency was also correlated with Dvein after considering phylogenetic effects. N resorption proficiency (N remaining in senesced leaves) was negatively correlated with Dvein, LMA, leaf thickness and palisade and spongy mesophyll thickness. Senesced‐leaf N concentration was still negatively correlated with LMA and leaf thickness after considering phylogenetic effects. N resorption efficiency was positively correlated with both height and diameter growth rates. After considering phylogenetic effect, N resorption efficiency was marginally correlated with diameter growth rate. Green‐leaf N concentration was positively correlated with height growth rate after considering phylogenetic effect. P resorption efficiency and proficiency were not related to any of the leaf morphological and anatomical traits, or to species growth rates. Synthesis. These results indicate that higher phloem transport capacity of the dipterocarp species is positively correlated with greater N resorption efficiency and that N resorption proficiency is closely linked with leaf nutrient conservation traits. Growth rates of the dipterocarps are more likely governed by photosynthetic rates associated with green‐leaf N concentration than N resorption rates per se. Although P is generally deficient in tropical soils, it appears that N rather than P availability is the key limiting factor for the growth of the dipterocarp species.

Biodiversity of leaf-litter ants in fragmented tropical rainforests of Borneo: the value of publically and privately managed forest fragments

In view of the rapid rate of expansion of agriculture in tropical regions, attention has focused on the potential for privately-managed rainforest patches within agricultural land to contribute to biodiversity conservation. However, these sites generally differ in their history of forest disturbance and management compared with other forest fragments, and more information is required on the biodiversity value of these privately-managed sites, particularly in oil-palm dominated landscapes of SE Asia. Here we address this issue, using tropical leaf-litter ants in rainforest fragments surrounded by mature oil palm plantations in Sabah, Borneo as a model system. We compare the species richness and composition of ant assemblages in privately-managed forest fragments (‘high conservation value’ fragments; HCVs) with those in publically-managed fragments of forest (virgin jungle reserves; VJRs) and control sites in extensive tracts of primary forest. In this way, we test the hypothesis that privately-managed and publically-managed forest fragments differ in their species richness and composition as a result of differences in history and management and hence in habitat quality. In support of this hypothesis, we found that HCVs had much poorer habitat quality than VJRs, including lower sizes and densities of trees, less canopy cover, fewer dipterocarp trees and shallower leaf litter. Consequently, HCVs supported only half the species richness of ants in VJRs, which in turn supported 70 % of the species richness of control sites, with vegetation structure and composition explaining 77 % of the variation among forest fragments in ant species richness. HCVs were also much smaller than VJRs but there was only a weak relationship between fragment size and habitat quality, and species richness was not related to fragment size. VJRs supported 78 % of the 156 species found in extensive tracts of forest whereas HCVs supported only 22 %, which was only slightly higher than the proportion previously recorded in oil palm (19 %). These data support previous findings that publically-managed VJR fragments can make an important contribution to biodiversity conservation within agricultural landscapes. However, we suggest that for these HCVs to be effective as reservoirs of biodiversity, management is required to restore vegetation structure and habitat quality, for instance through enrichment planting with native tree species.