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The role of conspecific density dependence (CDD) in the maintenance of species richness is a central focus of tropical forest ecology. However, tests of CDD often ignore the integrated effects of CDD over multiple life stages and their long-term impacts on population demography. We combined a 10-year time series of seed production, seedling recruitment and sapling and tree demography of three dominant Southeast Asian tree species that adopt a mast-fruiting phenology. We used these data to construct individual-based models that examine the effects of CDD on population growth rates ( λ ) across life-history stages. Recruitment was driven by positive CDD for all species, supporting the predator satiation hypothesis, while negative CDD affected seedling and sapling growth of two species, significantly reducing λ . This negative CDD on juvenile growth overshadowed the positive CDD of recruitment, suggesting the cumulative effects of CDD during seedling and sapling development has greater importance than the positive CDD during infrequent masting events. Overall, CDD varied among positive, neutral and negative effects across life-history stages for all species, suggesting that assessments of CDD on transitions between just two stages (e.g. seeds seedlings or juveniles mature trees) probably misrepresent the importance of CDD on population growth and stability.

This study was conducted in the alluvial forest and heath forest in the lowland tropical forest of Sepilok Forest Reserve, Sabah, Malaysia. The main objective was to assess how forest structure regulates rainfall partitioning in both forests. Field monitoring involved a series of forest inventory work to determine the forest stand characteristics. Mann Whitney U test was performed to compare physical characteristics between the two forests. Meanwhile rainfall partitioning was quantified by measuring the throughfall (Tf) for a period of 12 months in ten (15 x 15 m) Tf plots and a simple linear regression was conducted to obtain a regression model to estimate Tf. In terms of stand structure characteristics, data in the alluvial forest indicates wider variation. Percentage of Tf as of gross rainfall (Pg) is higher in the heath forest than in alluvial forest with the value of 89.5 % and 76.8 %, respectively. Representative trees were selected for stemflow (Sf) estimation at each forest type. The estimated Sf is 0.2 % in alluvial forest and 0.5 % in heath forest. In this study, tree diameter at breast height (Dbh) and height as well as aboveground biomass were identified to have some influence in Tf and Sf production. Keywords: rainfall partitioning; gross rainfall; throughfall; stemflow; Mann Whitney U; simple linear regression

Trade-offs in wood anatomical characteristics reflect different strategies used by trees to deal with water transport in response to variation in environmental conditions. To study vascular strategies for Bornean rainforest trees, we compared water transport-related anatomical characteristics in branch wood between the common tree species Vatica dulitensis (Dipterocarpaceae) from old-growth forest and the common pioneer tree species Macaranga gigantea (Euphorbiaceae) from selectively logged forest. We hypothesised that the vessel traits of the pioneer species would reflect the need to capture and transport resources to support its fast growth rate (resource-acquisitive strategy), while the species of the old-growth forest would display more conservative vessel traits (resource-conservative strategy). We found that M. gigantea had significantly greater vessel area, hydraulically weighted diameter, vessel area to number ratio, and potential hydraulic conductivity than V. dulitensis. These results suggest that vessel traits of the common old-growth species would ensure high hydraulic safety during occasional drought when soil moisture is limited, while the common species of selectively logged forest possesses an efficient water transport system but its vessels would confer lower hydraulic safety during drought conditions. These contrasting vascular strategies highlight the potential for divergent responses of species of Bornean forest trees to future climatic extremes.

Conservation planning tends to focus on protecting species' ranges or landscape connectivity but seldom both-particularly in the case of diverse taxonomic assemblages and multiple planning goals. Therefore, information on potential trade-offs between maintaining landscape connectivity and achieving other conservation objectives is lacking. We developed an optimization approach to prioritize the maximal protection of species' ranges, ecosystem types, and forest carbon stocks, while also including habitat connectivity for range-shifting species and dispersal corridors to link protected area. We applied our approach to Sabah, Malaysia, where the state government mandated an increase in protected-area coverage of approximately 305,000 ha but did not specify where new protected areas should be. Compared with a conservation planning approach that did not incorporate the 2 connectivity features, our approach increased the protection of dispersal corridors and elevational connectivity by 13% and 21%, respectively. Coverage of vertebrate and plant species' ranges and forest types were the same whether connectivity was included or excluded. Our approach protected 2% less forest carbon and 3% less butterfly range than when connectivity features were not included. Hence, the inclusion of connectivity into conservation planning can generate large increases in the protection of landscape connectivity with minimal loss of representation of other conservation targets.Incorporación de la Conectividad a la Planeación de la Conservación para la Representación Óptima de Especies Múltiples y Servicios Ambientales Resumen Las tendencias de planeación de la conservación tienden a enfocarse en la protección de la distribución geográfica de las especies o en la conectividad de paisajes, pero rara vez se enfocan en ambas - particularmente para el caso de los ensamblajes taxonómicos y las metas múltiples de planeación. Por lo tanto, hay carencias en la información sobre las compensaciones potenciales entre mantener la conectividad de los paisajes y alcanzar otros objetivos de conservación. Desarrollamos una estrategia de optimización para priorizar la protección máxima de la distribución de las especies, los tipos de ecosistemas y los stocks de carbono de los bosques, a la vez que incluimos la conectividad del hábitat para las especies que modifican su distribución y los corredores de dispersión para conectar el área protegida. Aplicamos nuestra estrategia en Sabah, Malasia, en donde el gobierno estatal ordenó un incremento de ∼305, 000 ha en la cobertura de áreas protegidas sin especificar la ubicación de las nuevas áreas protegidas. En comparación con una estrategia de planeación de la conservación que no incorporó las dos características de la conectividad, nuestra estrategia incrementó la protección de los corredores de dispersión y la conectividad altitudinal en un 13% y 21% respectivamente. La cobertura de la distribución de las especies de plantas y vertebrados y de los tipos de bosque fue la misma con o sin la inclusión de la conectividad. Nuestra estrategia protegió 2% menos del carbono forestal y 3% menos de la distribución de mariposas que cuando no se incluyeron las características de conectividad en la estrategia. Por lo tanto, incluir a la conectividad en la planeación de la conservación puede generar grandes incrementos en la protección de la conectividad del paisaje con una pérdida mínima de representación para los demás objetivos de conservación.

The sensitivity of tropical forest carbon to climate is a key uncertainty in predicting global climate change. Although short-term drying and warming are known to affect forests, it is unknown if such effects translate into long-term responses. Here, we analyze 590 permanent plots measured across the tropics to derive the equilibrium climate controls on forest carbon. Maximum temperature is the most important predictor of aboveground biomass (-9.1 megagrams of carbon per hectare per degree Celsius), primarily by reducing woody productivity, and has a greater impact per °C in the hottest forests (>32.2°C). Our results nevertheless reveal greater thermal resilience than observations of short-term variation imply. To realize the long-term climate adaptation potential of tropical forests requires both protecting them and stabilizing Earth's climate., Our plot monitoring networks havebeen supported by multiple grants from a large number of funding bodies: European Research Council; Natural Environment Research Council; European Union’s Fifth, Sixth, and Seventh Framework Programme; Royal Society, Leverhulme Trust; Gordon and Betty Moore Foundation; David and Lucile Packard Foundation; State of São Paulo Research Foundation (FAPESP); National Council for Science and Technology Development of Brazil (CNPq); Agence Nationale de la Recherche; Conservation International; Missouri Botanical Garden; Smithsonian Institution; Wildlife Conservation Society; National Geographic Society; Centre for International Forestry; and Gabon’s National Park Agency.

Background: Logging and habitat fragmentation of tropical rain forests may disrupt patterns of gene flow and genetic diversity. Consequently, inbreeding in tree populations may reduce fitness and increase extinction risks, especially among species that are predominantly outcrossing, dependent on biotic pollination and/or display limited seed dispersal such as species of the Dipterocarpaceae.Aims: To test the hypothesis that heterozygosity of individual progeny affects their likelihood of germination and the growth and survival of seedlings.Methods: Standardised measure of multilocus heterozygosity (sMLH) was estimated from seven microsatellite loci for individual progeny collected from 18 mother trees of the large dipterocarp Parashorea tomentella. The relationships among sMLH, germination and seedling growth and survival were determined for the progeny.Results: Seedling survival over 18 months increased with greater sMLH and fresh fruit weight. This result was expressed under all experimentally controlle...

Documenting the scale and intensity of fine-scale spatial genetic structure (FSGS), and the processes that shape it, is relevant to the sustainable management of genetic resources in timber tree species, particularly where logging or fragmentation might disrupt gene flow. In this study we assessed patterns of FSGS in three species of Dipterocarpaceae (Parashorea tomentella, Shorea leprosula and Shorea parvifolia) across four different tropical rain forests in Malaysia using nuclear microsatellite markers. Topographic heterogeneity varied across the sites. We hypothesised that forests with high topographic heterogeneity would display increased FSGS among the adult populations driven by habitat associations. This hypothesis was not supported for S. leprosula and S. parvifolia which displayed little variation in the intensity and scale of FSGS between sites despite substantial variation in topographic heterogeneity. Conversely, the intensity of FSGS for P. tomentella was greater at a more topographically heterogeneous than a homogeneous site, and a significant difference in the overall pattern of FSGS was detected between sites for this species. These results suggest that local patterns of FSGS may in some species be shaped by habitat heterogeneity in addition to limited gene flow by pollen and seed dispersal. Site factors can therefore contribute to the development of FSGS. Confirming consistency in species’ FSGS amongst sites is an important step in managing timber tree genetic diversity as it provides confidence that species specific management recommendations based on species reproductive traits can be applied across a species’ range. Forest managers should take into account the interaction between reproductive traits and site characteristics, its consequences for maintaining forest genetic resources and how this might influence natural regeneration across species if management is to be sustainable. ISSN:1932-6203

We measured the terminal velocity of helicopter-like fruit from the Dipterocarpaceae family and present a model predicting the terminal velocities for all dipterocarp species in the Malesiana region. A ballistic model of seed dispersal using the observed terminal velocities predicted dispersal distances of 17–77 m under normal atmospheric conditions. These data are of applied use in parametizing models of species coexistence, forest regeneration and habitat connectivity in Southeast Asian tropical forests. Abstrak Kami telah melakukan pengiraan untuk menguji halaju terminal (terminal velocity) pada buah dari keluarga Dipterocarpaceae di Malaysia dan membentangan kertas kerja ini bagi tujuan untuk menunjukkan keputusan yang telah diperolehi. Dengan menggunakan Model Ballistik, penyebaran biji melalui pemerhatian halaju terminal (terminal velocitiy), penyebaran biji mampu dilakukan pada jarak 17m hingga 77m dalam keadaan cuaca yang normal. Data-data yang dihasilkan dari penelitian ini dapat digunakan untuk menguji “species coexistence”, pertumbuhan semula hutan dan pertalian habitat (habitat connectivity) Hutan Tropika di Asia Tenggara.

The lowland tropical forests of Southeast Asia are dominated by a single family of canopy and emergent trees, the Dipterocarpaceae. The seeds of dipterocarps are gravity or gyration dispersed. Short distance and limited seed dispersal via these mechanisms result in the aggregation of related individuals and strong fine-scale spatial genetic structure (FSGS). In logged and fragmented forests, where gene flow may be disrupted, tree species with strong FSGS are predicted to exhibit increased inbreeding, which consequently can erode genetic diversity, fitness and might limit the potential for natural regeneration of dipterocarps. Developing a set of indirect operational indicators for FSGS provides a solid basis for informing conservation and management of forest genetic resources in logged forests. Our main objective was to use an information theoretic approach to identify these indicators of FSGS in dipterocarps. We quantify FSGS in 19 dipterocarp species across four forest sites in Malaysian Borneo, India and the Seychelles. We detected FSGS in 15 (79%) of our study species, most of which displayed significant inbreeding. Our results suggest that wood density and flower size offer useful indicators of FSGS. We propose some simple guidelines to allow forest managers to account for FSGS when planning approaches to maintain genetically diverse stands in logged dipterocarp forests. The integration of improved understanding of genetic processes is essential for conserving forest tree genetic resources and ensuring the resilience of logged forests.

Less than half of anthropogenic carbon dioxide emissions remain in the atmosphere. While carbon balance models imply large carbon uptake in tropical forests, direct on-the-ground observations are still lacking in Southeast Asia. Here, using long-term plot monitoring records of up to half a century, we find that intact forests in Borneo gained 0.43 Mg C ha−1 per year (95% CI 0.14–0.72, mean period 1988–2010) in above-ground live biomass carbon. These results closely match those from African and Amazonian plot networks, suggesting that the world’s remaining intact tropical forests are now en masse out-of-equilibrium. Although both pan-tropical and long-term, the sink in remaining intact forests appears vulnerable to climate and land use changes. Across Borneo the 1997–1998 El Niño drought temporarily halted the carbon sink by increasing tree mortality, while fragmentation persistently offset the sink and turned many edge-affected forests into a carbon source to the atmosphere., The existence of a pan-tropical forest carbon sink remains uncertain due to the lack of data from Asia. Here, using direct on-the-ground observations, the authors confirm remaining intact forests in Borneo have provided a long-term carbon sink, but carbon net gains are vulnerable to drought and edge effects.

The frequency of extreme precipitation events is predicted to increase in some tropical regions in response to global climate change, but the impacts of this form of disturbance on the structure and dynamics of tropical tree communities across heterogeneous landscapes remain understudied. We determined the effects of an extreme precipitation event (EPE) in July 2006 on mortality of dipterocarps on a 68 ha permanent inventory plot in Sepilok Forest Reserve, Sabah. For stems ≥30 cm dbh, 12 of the 15 species of Dipterocarpaceae on this plot have significant positive and/or negative associations to habitats defined by topography and soil type. Short-term mortality induced by the EPE was much greater for individuals growing on the alluvial floodplain (13.7%) than in the mudstone (1.4%) or sandstone (0.0%) habitats, but mortality of dipterocarps did not differ among these habitats in the subsequent 5-yr interval. The likelihood of mortality in response to the EPE was highest for a small group of fast growing dipterocarps that possess low wood density and a strong association to the alluvial forest habitat. This group of species represents a high percentage of dipterocarp individuals but a low proportion of dipterocarp diversity in this habitat. We conclude that disturbance induced by high rainfall events contributes to the episodic nature of tropical forest dynamics, and that increases in the frequency of these events would disproportionately impact low-lying alluvial forest environments and some of the species growing in them.

Developing a robust and cost-effective method for accurately estimating tropical forest’s carbon pool over large area is a fundamental requirement for the implementation of Reducing Emissions from Deforestation and forest Degradation (REDD+). This study aims at examining the independent and combined use of airborne LiDAR and Landsat 8 Operational Land Imager (OLI) data to accurately estimate the above-ground biomass (AGB) of primary tropical rainforests in Sabah, Malaysia. Thirty field plots were established in three types of lowland rainforests: alluvial, sandstone hill and heath forests that represent a wide range of AGB density and stand structure. We derived the height percentile and laser penetration variables from the airborne LiDAR and calculated the vegetation indices, tasseled cap transformation values, and the texture measures from Landsat 8 OLI data. We found that there are moderate correlations between the AGB and laser penetration variables from airborne LiDAR data (r = −0.411 to −0.790). For Landsat 8 OLI data, the 6 vegetation indices and the 46 texture measures also significantly correlated with the AGB (r = 0.366–0.519). Stepwise multiple regression analysis was performed to establish the estimation models for independent and combined use of airborne LiDAR and Landsat 8 OLI data. The results showed that the model based on a combination of the two remote sensing data achieved the highest accuracy (R2adj = 0.81, RMSE = 17.36%) whereas the models using Landsat 8 OLI data airborne LiDAR data independently obtained the moderate accuracy (R2adj = 0.52, RMSE = 24.22% and R2adj = 0.63, RMSE = 25.25%, respectively). Our study indicated that texture measures from Landsat 8 OLI data provided useful information for AGB estimation and synergistic use of Landsat 8 OLI and airborne LiDAR data could improve the AGB estimation of primary tropical rainforest.

Niche differentiation is a prominent mechanism for explaining tree species coexistence in tropical rain forests. Theory predicts that species that are specialized on a set of environmental conditions should competitively exclude generalists in those conditions, and that environmental heterogeneity allows the coexistence of many different species based on niche specialization. Yet, many tropical tree species of the family Dipterocarpaceae have broadly similar habitat preferences, with some occurring widely across several soil types. These soil generalists clearly persist despite the presence of other dipterocarp species that show clear soil specialization. We evaluate comparative seedling performance (growth and survival) of six Shorea species (Dipterocarpaceae) which differ in their adult tree habitat associations within the Sepilok Forest Reserve (Borneo, Malaysia). We tested the hypothesis that seedlings of species associated with a particular soil type perform better on that soil type than seedlings of soil generalist species, with generalists in turn performing better than specialists on a different soil type. We conducted a reciprocal transplant experiment including two soil types (alluvial and mudstone) and two light treatments (gap and understory). The soils differed in soil acidity, Al and P concentration. Observed species-specific differences in seedling responses to soil, light, and occasional flooding events could partially explain observed adult distribution, although not all species could be fully differentiated along these axes. Other trade-offs, such as investment in defense against herbivores and tolerance to soil waterlogging, may play additional roles in explaining coexistence of these species. Abstrak Perbezaan nic adalah mekanisme penting untuk menjelaskan kewujudan bersama spesies-spesies pokok dalam hutan hujan tropika. Secara teorinya adalah diramalkan bahawa spesies spesialis kepada satu set keadaan persekitaran akan bersaing secara kompetitif dan menolak kewujudan spesies generalis dalam set keadaan persekitaran yang sama, dan kepelbagaian alam sekitar membolehkan kewujudan bersama kebanyakan spesies yang berbeza berdasarkan spesialisasi nic. Bagaimanapun, kebanyakan spesies pokok tropika dari famili Dipterocarpaceae mempunyai keutamaan pilihan habitat yang sama, dan ada beberapa spesies yang lain dijumpai secara meluas di beberapa jenis tanah. Pertumbuhan berterusan spesies generalis sangat jelas walaupun adanya kehadiran spesies dipterokarpa yang lain yang menunjukkan spesialisasi tanah yang jelas. Kami menilai perbandingan pertumbuhan anak benih (tumbesaran dan kemandirian) daripada enam spesies Shorea (Dipterocarpaceae) yang berbeza dalam taburan habitat pokok dewasa di dalam Hutan Simpan Sepilok (Borneo, Malaysia). Kami menguji hipotesis bahawa anak benih spesies yang berasiosasi dengan jenis tanah tertentu akan menunjukkan prestasi pertumbuhan yang lebih baik daripada benih spesies generalis, dan seterusnya spesies generalis menunjukkan prestasi pertumbuhan yang lebih baik daripada spesies spesialis di tanah yang berbeza. Kami telah menjalankan satu eksperimen pemindahan tanaman dua hala dengan melibatkan dua jenis tanah (aluvium dan batu-lumpur) dan dua rawatan cahaya (kawasan luang dan kanopi bawah). Kedua-dua tanah tersebut berbeza dalam nilai keasidan tanah, dan kepekatan Al dan P. Diperhatikan adanya perbezaan mengikut spesies-spesifik dalam tindakbalas anak benih dengan keadaan tanah, cahaya dan peristiwa banjir yang kadang-kadang berlaku, dan ini dapat menjelaskan sebahagian pemerhatian pengagihan taburan pokok dewasa, walaupun tidak semua spesies menunjukkan pembezaan yang nyata. Lain-lain proses keseimbangan, seperti keupayaan tumbuhan dalam mencegah impak haiwan perosak dan daya ketahanan ditenggelami oleh banjir boleh memainkan peranan tambahan dalam menjelaskan kewujudan bersama spesies-spesies berkenaan.

Sabah has experienced a rapid decline in the extent of forest cover. The precise impact of habitat loss on the conservation status of the plants of Sabah is uncertain. In this study we use the niche modelling algorithm MAXENT to construct preliminary, revised and final ecological niche models for Dipterocarpus lamellatus and Dipterocarpus ochraceus and combined these models with data on current land-use to derive conservation assessments for each species. Preliminary models were based on herbarium data alone. Ground surveys were conducted to evaluate the performance of these preliminary models, and a revised niche model was generated from the combined herbarium and ground survey data. The final model was obtained by constraining the predictions of the revised models by filters. The range overlap between the preliminary and revised models was 0.47 for D. lamellatus and 0.39 for D. ochraceus, suggesting poor agreement between them. There was substantial variation in estimates of habitat loss for D. ochraceus, among the preliminary, revised and constrained models, and this has the potential to lead to incorrect threat assessments. From these estimates of habitat loss, the historic distribution and estimates of population size we determine that both species should be classified as Critically Endangered under IUCN Red List guidelines. Our results suggest that ground-truthing of ecological niche models is essential, especially if the models are being used for conservation decision making.

Borneo has experienced a rapid decline in the extent of forest cover, which has reduced the amount of habitat available for many plant and animal species. The precise impact of habitat loss on the conservation status of dipterocarp trees is uncertain. We use three contrasting techniques, the extent of occurrence, area of occupancy and ecological niche models derived using maxent, in conjunction with a current land-use map of Sabah, to derive estimates of habitat loss and infer a regional IUCN Red List conservation status for 33 Sabah dipterocarp species. Estimates of habitat loss differed significantly according to the methods employed and between species on different habitat types. Proportion of habitat loss determined from the ecological niche models varied from 21 percent for Shorea micans to 99.5 percent for Dipterocarpus lamellatus. Thirty-two of the 33 dipterocarp species analyzed in this study would have their Sabah populations classified as Threatened (equal to a habitat loss of > 30%) under the A2 IUCN Red List criterion. Dipterocarps that occur in lowland forests have experienced greater habitat loss than upland/lower montane or ultramafic species. In addition, species with the lowest predicted area within their historic distributions had the highest proportion of habitat lost, which provides a rationale for targeting conservation effort on the species with narrow distributions. We recommend the ecological niche modeling approach as a rapid assessment tool for reconstructing species’ historic distributions during conservation assessments of tropical trees.

Fine-scale spatial genetic structure (FSGS) within plant populations is an emergent property of the recruited adult trees, influenced by pollen and seed mediated gene flow, selection and demographic processes. This study aims to increase our understanding of the individual species traits that contribute to the generation of FSGS in the Dipteropcarpaceae, which is an ecologically and economically important family of tropical trees that dominate lowland forests in Southeast Asia. We examined FSGS in three cooccurring dipterocarp species at a single site in Borneo. Shorea xanthophylla, Parashorea tomentella and Dipterocarpus grandiflorus share limited seed dispersal but differ markedly in flower size, pollinator body size and pollen dispersal. Here we explore the role of pollen dispersal limitation in shaping FSGS in these three species. Using six microsatellite loci, we explore patterns of FSGS and landscape genetic structure and compare these across species. Significant FSGS was observed in S. xanthophylla and P. tomentella, both of which are known to have relatively limited pollen dispersal, but no clear signal of FSGS was observed in D. grandiflorus. Significantly greater FSGS was observed in P. tomentella (Sp = 0.012) than S. xanthophylla (Sp = 0.007) despite greater pollen dispersal in P. tomentella. Bayesian clustering analysis revealed significant structure in P. tomentella at the scale of the forest reserve (4000 ha). We discuss the alternative explanations for the observed patterns of FSGS emphasising the complexity of the mechanisms that can generate FSGS in long-lived trees. The extent of species-specific pollen dispersal is one factor that can contribute to differences in FSGS across species, but is not the only determinant. The observed patterns of FSGS and landscape scale genetic structure in S. xanthophylla and P. tomentella illustrate the potential of gap regeneration to counter act pollen dispersal and contribute to increased aggregation of related individuals (FSGS). © 2010 Elsevier GmbH. All rights reserved.

The recent mass fruiting of forest trees in Borneo is an urgent wakeup call: existing policy instruments, financial mechanisms, and forestry infrastructure are inadequate to take full advantage of these infrequent opportunities for forest restoration and conservation. Tropical forest restoration can provide substantial benefits for biodiversity conservation, climate change mitigation, and poverty alleviation. Yet the unpredictability of the synchronized flowering and consequent mass fruiting of many forest trees in Borneo presents a distinctive set of challenges for forest restoration. Significant financing and a considerable coordinated effort are required to prepare for future mass fruiting events if we are to capitalize on opportunities for ecological restoration. The continued high rate of forest clearance in this region and the rarity of mass fruiting events suggest that there may be few remaining opportunities to prevent widespread species extinctions. In this article we propose a facilitatory policy framework for forest restoration in Borneo to stimulate action in advance of the next mass fruiting of forest trees.

The Dipterocarpaceae is an ecologically and economically important tree family in Southeast Asia. In this article, we synthesize the contributions to our understanding of the population genetics, ecology, and conservation of the family presented in this Special Section, and discuss their implications for mechanisms of dipterocarp species coexistence in natural and disturbed forests. We highlight the need for research to address how the processes that give rise to dipterocarp diversity are maintained in landscapes modified by anthropogenic activity.

Background In angiosperms, flower size commonly scales negatively with number. The ecological consequences of this trade-off for tropical trees remain poorly resolved, despite their potential importance for tropical forest conservation. We investigated the flower size number trade-off and its implications for fecundity in a sample of tree species from the Dipterocarpaceae on Borneo. Methodology/Principal Findings We combined experimental exclusion of pollinators in 11 species, with direct and indirect estimates of contemporary pollen dispersal in two study species and published estimates of pollen dispersal in a further three species to explore the relationship between flower size, pollinator size and mean pollen dispersal distance. Maximum flower production was two orders of magnitude greater in small-flowered than large-flowered species of Dipterocarpaceae. In contrast, fruit production was unrelated to flower size and did not differ significantly among species. Small-flowered species had both smaller-sized pollinators and lower mean pollination success than large-flowered species. Average pollen dispersal distances were lower and frequency of mating between related individuals was higher in a smaller-flowered species than a larger-flowered confamilial. Our synthesis of pollen dispersal estimates across five species of dipterocarp suggests that pollen dispersal scales positively with flower size. Conclusions and Their Significance Trade-offs embedded in the relationship between flower size and pollination success contribute to a reduction in the variance of fecundity among species. It is therefore plausible that these processes could delay competitive exclusion and contribute to maintenance of species coexistence in this ecologically and economically important family of tropical trees. These results have practical implications for tree species conservation and restoration. Seed collection from small-flowered species may be especially vulnerable to cryptic genetic erosion. Our findings also highlight the potential for differential vulnerability of tropical tree species to the deleterious consequences of forest fragmentation. ISSN:1932-6203

Unprecedented deforestation and forest degradation in recent decades have severely depleted the carbon storage in Borneo. Estimating aboveground biomass (AGB) with high accuracy is crucial to quantifying carbon stocks for Reducing Emissions from Deforestation and Forest Degradation-plus implementation (REDD+). Airborne Light Detection and Ranging (LiDAR) is a promising remote sensing technology that provides fine-scale forest structure variability data. This paper highlights the use of airborne LiDAR data for estimating the AGB of a logged-over tropical forest in Sabah, Malaysia. The LiDAR data was acquired using an Optech Orion C200 sensor onboard a fixed wing aircraft. The canopy height of each LiDAR point was calculated from the height difference between the first returns and the Digital Terrain Model (DTM) constructed from the ground points. Among the obtained LiDAR height metrics, the mean canopy height produced the strongest relationship with the observed AGB. This single-variable model had a root mean squared error (RMSE) of 80.02 t ha-1 or 22.31% of the mean AGB, which performed exceptionally when compared with recent tropical rainforest studies. Overall, airborne LiDAR did provide fine-scale canopy height measurements for accurately and reliably estimating the AGB in a logged-over forest in Sabah, thus supporting the state's effort in realizing the REDD+ mechanism.

[Extract] The development of an extensive surface root mat is one of the major mechanisms that enhances nutrient conservation in tropical rain forest, particularly in ecosystems growing on nutrient-poor, heavily leached soils (Jordan & Herrera 1981, Cuevas & Medina 1988). In these root mats, it is the fine unsuberized roots that are primarily responsible for the retention of nutrients (Edwards & Grubb 1982, Gower 1987, Berish & Ewe1 1988). The level of development of these fine root mats has been found to be very variable within the tropics, with the biomass of roots

The stem allometry (tree height versus stem diameter) of four tree species found in a North Queensland rainforest was examined. These species were dicotyledonous trees, two of which were classed as early successional species and two as later successional species. No significant differences (P > 0.05) were found in the stem allometry of dicoty¬ledonous trees of the same successional status. However, significant differences (P < 0.05) in stem allometry were found when comparing species of different successional status. Later successional species, but not early successional species, were found to be "elastically similar" to a theoretical buckling limit. The relationship between stability safety factors and tree height indicated that both early and later successional species have large buckling safety margins when of low stature. At medium statures (subcanopy), early successional species display a moderate buckling safety margin while later successional species exhibited their lowest buckling safety margin. At tall statures (canopy and above), early successional species exhibited their lowest buckling safety margin while later successional species had moderate buckling safety margins. Stem allometry may be influenced by a tree's life-span, wood density, and environmental conditions in its crown region.

[Figure][1] Dipterocarp tree seedlings. Many endangered Indonesian trees rarely produce seeds. CREDIT: CAMPBELL WEBB Large-scale restoration of tropical forest is increasingly recognized as a credible option for climate change mitigation and biodiversity conservation ([ 1 ][2]–[ 3 ][3