Lowland Forest Research Articles

Tree growth and survival are more sensitive to high rainfall than drought in an aseasonal forest in Malaysia

Global change research has largely focused on the effects of drought on forest dynamics while the importance of excessive rainfall that can cause waterlogged soils has largely been assessed in riparian zones or seasonally flooded sites. However, increased rainfall may also cause decreased growth and survival of tree species in lowland aseasonal tropical forests due to increased risk from potentially more extensive and frequent waterlogged soils. We used a Bayesian modelling approach on a tree dynamics dataset from 2004 to 2017 to test the concomitant effects of rainfall excess and deficit and dry period length on tree growth and survival across a network of experimentally planted trees in a primary aseasonal forest in Malaysia. Growth declined in 48% of the species and survival decreased in 92% of the species during periods of high rainfall while as little as 4% of species had decreased growth or survival with drought and long dry periods. Climate change is projected to cause more frequent and severe rainfall deficit and excess, and our results suggest increased rainfall may have stronger negative effects on aseasonal tropical forests than that of severe drought.

ANALISIS KONDISI SOSIAL EKONOMI MASYARAKAT SEKITAR TAMAN NASIONAL GANDANG DEWATA

Gandang Dewata National Park was designated as a conservation area because it has biodiversity and a unique ecosystem. Ecosystem types in this area are based on altitude or topographic conditions, namely Lowland Forest, Lower Mountain Forest, Upper Mountain Forest and Sub-Alpine Forest. This research aims to obtain an explanation of the socio-economic problems of the community around the Gandang Dewata National Park (TNGD), the level of community dependence on the National Park area and the contribution of income from the park to the total income of farmers. The research was carried out in Mamasa Regency in the TNGD Area, West Sulawesi Province. The method used in this research is interviews. Respondents in this study were chosen randomly. Data was analyzed descriptively qualitatively and quantitatively. The results of this research show that basic data and information regarding the socio-economic conditions of the people of Taupe Village, one of the TNGD buffer villages, shows that out of the 84 respondents interviewed, the socio-economic conditions of the people of Taupe Village work as farmers. 90% of this is because the village's irrigation conditions are still in good condition. The community is dependent on the area, namely 56% know the village boundaries and the location where the community lives is outside the area. Apart from that, the community's dependence on forests consists of rice fields and gardens. Utilization of forest products in the form of firewood, honey, aloes, bamboo, rattan and game products. Commodities based on agricultural, livestock, plantation and forestry products are coffee, cloves, cinnamon, patchouli, honey, cassava pork, aloes and broiler chicken. Most people (77%) do not know about TNGD

Four new species close to Sonitha libera and Sonitha myoctona from the Congolian lowland forests (Lepidoptera, Lasiocampidae)

Four new species of the genus Sonitha Zolotuhin & Prozorov, 2010 are described: Sonitha adedapo sp. n. from Nigeria, Gabon, and DRC; Sonitha bekombo sp. n. and Sonitha ekongo sp. n. from DRC; and Soniha olanrewaju sp. n. from Nigeria and DRC. The new species are compared with closely related Sonitha libera (Aurivillius, 1915) and Sonitha myoctona Zolotuhin & Prozorov, 2010. Male adults, genitalia and maps with collecting localities are presented.

Vertical stratification and defensive traits of caterpillars against parasitoids in a lowland tropical forest in Cameroon

Insect herbivores and their parasitoids play a crucial role in terrestrial trophic interactions in tropical forests. These interactions occur across the entire vertical gradient of the forest. This study compares how caterpillar communities, and their parasitism rates, vary across vertical strata and between caterpillar defensive strategies in a semi deciduous tropical forest in Nditam, Cameroon. Within a 0.1 ha plot, all trees with a diameter at breast height (DBH) ≥ 5 cm were felled and systematically searched for caterpillars. We divided the entire vertical gradient of the forest into eight, five-metre strata. All caterpillars were assigned to a stratum based on their collection height, reared, identified, and classified into one of three defensive traits: aposematic, cryptic and shelter-building. Caterpillar species richness and diversity showed a midstory peak, whereas density followed the opposite pattern, decreasing in the midstory and then increasing towards the highest strata. This trend was driven by some highly dense shelter-building caterpillars in the upper canopy. Specialisation indices indicated decreasing levels of caterpillar generality with increasing height, a midstory peak in vulnerability, and increasing connectance towards the upper canopy, although the latter was likely driven by decreasing network size. Both aposematic and shelter-building caterpillars had significantly higher parasitism rates than cryptic caterpillars. Our results highlight nuanced changes in caterpillar communities across forest strata and provide evidence that defences strategies are important indicators of parasitism rates in caterpillars and that both aposematic and shelter-building caterpillars could be considered a “safe haven” for parasitoids.

Mapping the way: identifying priority potential corridors for protected areas connectivity in Colombia

Colombia has experienced alarming rates of deforestation, posing a threat to forest biodiversity both inside and outside protected areas. Furthermore, a decline in ecological connectivity can potentially disrupt vital ecological processes such as pollination, gene flow, breeding, seed dispersal, among others. To address this issue at a national scale, it is crucial to identify and conserve a comprehensive network of ecological corridors.In this study, we identified high priority potential ecological corridors linking protected areas in Colombia. We categorized a representative set of 16 threatened mammal species into four ecological profiles. Then, we used Least Cost Path (LCP) analysis to model potential corridors between protected areas as those that minimized resistance for forest species dispersal. To prioritize conservation efforts, we applied the decrease in the Probability of Connectivity index (dPC) to identify corridors with the highest priority.Our findings emphasize the importance of preserving large forest patches within protected areas for species inhabiting lowland and sub-Andean forests. However, for species residing in Andean and high Andean forests, restoration measures (e.g., increasing forest cover) between protected areas are needed to enhance landscape permeability and facilitate their dispersal, thereby contributing to their conservation.Our results have practical implications for decision-makers involved in conservation efforts. These findings can aid in identifying conservation priorities for existing protected areas and their surrounding forest habitats in Colombia. Additionally, we provided expert-based resistance values for different forest mammals that can be further used in other large scale connectivity analyses, including other countries where these species inhabit.

Successional dynamics of carbon sequestration in forests of the eastern United States

AbstractCarbon sequestration in the forests of the eastern United States is an important offset to the country's CO2 emissions. Much of the eastern forestland is the product of reforestation of abandoned agricultural land or recovery following clear‐cutting over a century ago. This has led to concerns that eastern forests are even‐aged and that rates of carbon sequestration will decline as forests increase in carbon. Our objective was to examine the successional dynamics of forest carbon sequestration—using live tree carbon stocks as a proxy for successional status—for the six broadly defined forest types present in the region. We used datasets from the National Forest Inventory (NFI) for the 31 US states from Minnesota south to Louisiana and eastward and analyzed live tree net carbon increment for 2007–2021, the period for which NFI plot remeasurement data were available for all 31 states. Spruce–fir and southern pines were the only forest types for which carbon increment declined even modestly over a significant fraction of the range of live tree carbon observed in the region, and southern pine–hardwood forests were the only forests in which predicted sequestration in live tree carbon declined to zero within the range of carbon stocks observed in the region. Northern hardwood–conifer forests, oak–hickory forests, and lowland forests experienced either no decline or a slight increase in sequestration in live tree carbon across the range of successional status observed in the region. Thus, the average stocks of live tree carbon per unit area increased steadily over the study period. At some point in succession, rates of mortality are expected to increase and balance gross growth, leading to zero net sequestration in live tree carbon. Mature and old‐growth stands, however, are rare in all six forest types, and mortality as a fraction of live tree carbon for all six forest types declined across the range of successional status present in the region. Our results thus provide no support for the hypothesis that the successional dynamics of forests in this region can be expected to lead to near‐term declines in net carbon sequestration.

Metals Accumulation of Tropical Shrub Melastoma malabathricum L. (Melastomataceae) Populations and Their Relation To Soil Edaphic Factor

Melastoma malabathricum L. (Melastomataceae) is a widely distributed tropical shrub that grows in Southeast Asia. Recent research found that M. malabathricum has a bioremediatory potential that can accumulate high concentrations of toxic metals such as Al, Pb, As, and Cr. Thus, this study aimed to investigate the metal hyperaccumulation in M. malabathricum from various populations and their relation to soil edaphic factors. We collected mature leaves and soils of M. malabathricum from 15 different populations in Negeri Sembilan, Selangor, and Pahang in Peninsular Malaysia. These 15 populations consist of lowland forests, dump sites, riparian, oil palm and rubber plantations, paddy fields, and mining sites. We found that M. malabathricum accumulated high concentrations of Al (3.45±1.58 to 8.697±1.61 mg g-1) followed by Fe (1.02±0.02 to 1.07±0.04 mg g-1), Pb (0.013±0.001 to 0.016±0.001 mg g-1), As (0.008±0.005 to 0.23±0.004 mg g-1), and Cr (0.005±0.0003 to 0.02±0.01 mg g-1). The highest concentration of soil Al was 85.95±5.00 mg g-1, Fe with 69.960±7.47mg g-1, Pb with 0.192±0.03 mg g-1, As with 0.156±0.06 mg g-1 and Cr with 0.133±0.03 mg g-1. We found no significant association between high foliar metal concentrations of the metals (Al, Pb, As & Cr) with the soil chemical properties but some soil metal elements were intercorrelated with foliar metal concentrations. Understanding the potential of M. malabathricum in accumulating high levels of metal elements, provides useful information for phytoremediation works. Further research is required to investigate the mechanism uptake and tolerance of heavy metals in M. malabathricum.

Mixed signals of environmental change and a trend towards ecological homogenization in ground vegetation across different forest types

Forest ground vegetation may serve as an early warning system for monitoring anthropogenic global-change impacts on temperate forests. Climate warming may induce a decline of cool-adapted species to the benefit of more thermophilous plants. Nitrogen deposition has been documented to potentially result in soil eutrophication or acidification, which can increase the proportion of species with higher nutrient requirements and species impoverishment caused by competitive exclusion. Abiotic forest disturbances are changing the light conditions in the forest understorey environment. In this resurvey study, we tested the magnitude and direction of change in alpha (species richness) and beta (within-site dissimilarity) diversity and composition of forest ground vegetation in forests of different types in Slovenia over fifteen years. Using plant-derived characteristics (Ellenberg-type indicator values) and by testing a priori predictions concerning expected effects of environmental drivers, we show that the magnitude and direction of forest ground vegetation diversity and floristic changes varies greatly between forest sites. Divergent responses at different sites resulted in low net change of alpha and beta diversity and a weak overall environmental signal. The largest decrease in species number was observed in lowland oak-hornbeam forests, which were also among the sites with the greatest compositional shifts. Changes in beta diversity did not show any consistent trend, and anticipated floristic convergence was not confirmed when all sites were considered. Thermophilization was mainly detected in montane beech sites and alpine spruce forests whereas eutrophication signal was most significant on nutrient-poor sites. Vegetation responses were strongly dependent on initial site conditions. Shrinkage of ecological gradients (process of ecological homogenization) suggests that sites positioned at the ends of the gradients are losing their original ecological character and are becoming more similar to mid-gradient sites that generally exhibit smaller changes. Our results point to the importance of local stand dynamics and overstorey disturbances in explaining the temporal trends in forest ground vegetation. Ground vegetation in Slovenian forests is changing in directions also dictated by multiple regional and global change drivers.

Sonitha adetoun – a new species from the Congolian lowland forests (Lepidoptera, Lasiocampidae, Lasiocampinae, Gastropachini)

A new species Sonitha adetoun sp. n. is described from the Congolian lowland forests. It is compared with closely related Sonitha lila Zolotuhin & Prozorov, 2010 and Sonitha integra Zolotuhin & Prozorov, 2010. Adults, genitalia and maps with collecting sites are illustrated.

Variations in Wood Anatomy in Afrotropical Trees with a special emphasis on radial and axial parenchyma.

Understanding anatomical variations across plant phylogenies and environmental gradients is vital for comprehending plant evolution and adaptation. Prior studies on tropical woody plants have paid limited attention to quantitative differences in major xylem tissues, which serve specific roles in mechanical support (fibers), carbohydrate storage and radial conduction (radial parenchyma, rays), wood capacitance (axial parenchyma), and water transport (vessels). To address this gap, we investigate xylem fractions in 173 tropical tree species spanning 134 genera and 53 families along a 2200 m elevational gradient on Mount Cameroon, West Africa. We determined how elevation, stem height, and wood density affect interspecific differences in vessel, fiber, and specific axial (AP) and radial (RP) parenchyma fractions. We focus on quantifying distinct subcategories of homogenous or heterogeneous rays and apotracheal, paratracheal, and banded axial parenchyma. Elevation-related cooling correlated with reduced AP fractions and vessel diameters, while fiber fractions increased. Lower elevations exhibited elevated AP fractions due to abundant paratracheal and wide-banded parenchyma in tall trees from coastal and lowland forests. Vasicentric and aliform AP were predominantly associated with greater tree height and wider vessels, which might help cope with high evaporative demands via elastic wood capacitance. In contrast, montane trees featured a higher fiber proportion, scarce axial parenchyma, smaller vessel diameters, and higher vessel densities. The lack of AP in montane trees was often compensated by extended uniseriate ray sections with upright or squared ray cells or the presence of living fibers. Elevation gradient influenced specific xylem fractions, with lower elevations showing elevated AP due to abundant paratracheal and wide-banded parenchyma, securing greater vessel-to-parenchyma connectivity and lower embolism risk. Montane trees featured a higher fiber proportion and smaller vessel diameters, which may aid survival under greater environmental seasonality and fire risk.

First record of the genus Pygoluciola Wittmer (Coleoptera: Lampyridae: Luciolinae) from Sri Lanka with two new species, P. rammale and P. ruhuna

We present the first record of the Southeast Asian firefly genus, Pygoluciola Wittmer, 1939 from Sri Lanka with descriptions of two new distinctive yellow species, P. rammale Wijekoon & De Silva sp. nov. and P. ruhuna Wijekoon & De Silva sp. nov. Both species are from a low-land forest in Southern Province, Sri Lanka, and females were associated with males when captured together in copula. An updated list of species, and key to males and known females of Pygoluciola is presented.

The Diversity of Butterflies (Order: Lepidoptera) in Pondok Ambung, Tanjung Puting National Park, Kalimantan Tengah

National parks are one of a site to maintain biodiversity from any damage. Tanjung Puting National Park is one of the national parks in Indonesia with a wide variety of biodiversity, namely butterflies. The aims of this study were to determine the diversity of butterfly species in 5 sub-ecosystems in Tanjung Puting National Park. The five sub-ecosystems are Camp Ambung, post-burn forest, heath forest, lowland forest and swamp forest. In this study, the butterflies were caught through the hunting method by using insect nets and the trapping method by installing food traps. This study was conducted from February to March 2022 for twice times a day from 8 to 12 in the morning and 1 to 5 in the afternoon. The results showed that butterflies collected were 121 species of butterflies from 6 families in Pondok Ambung, Tanjung Puting National Park. In detail, there were 88 species in Camp Ambung, 19 species in the post-burn forest, 14 species in the heath forest, 65 species in the lowland forest, and 38 species in the swamp forest. The diversity index from highest to lowest was Camp Ambung (3.71), lowland forest (3.49), swamp forest (3.02), post-burn forest (2.61), and heath forest (2.36).

Sharp declines in observation and capture rates of Amazon birds in absence of human disturbance

Across the globe, unprecedented declines have been reported across a range of taxa. Among the most well documented are declines in bird populations, with most declines attributable to human activities such as deforestation and other alterations to habitats. There is increasing evidence that bird populations also have declined at sites within large expanses of relatively undisturbed lowland tropical forest, such as in Amazonia. Causes of such declines likely are varied and may be related to direct or indirect effects of climate change. Here, we use mist-net data and direct observations to examine changes in bird numbers over a 22-yr period on two 100-ha study plots in an Amazonian lowland forest of eastern Ecuador. As previously reported, capture rates experienced large declines from 2009 on; observation rates also showed large declines through 2013 but subsequently have shown no consistent trend up or down. Overall capture rates and observation rates are now approximately half the rates during the first decade. Most foraging guilds also declined over time, with declines particularly pronounced among insectivorous groups. With few exceptions, patterns of change were similar between plots suggesting a more general response rather than responses to local factors on each plot. Capture rates and observation rates of ∼90% of the most common species in both understory and canopy were lower during the latter part of the study, with only a few species (∼10%) showing increases. Similarly, large declines were seen in both canopy and understory mixed-species flocks. Large declines in bird numbers have been noted in other tropical sites that have conducted long-term population studies, including Panama and Brazil, suggesting a response to large-scale factors, such as climate change. While not yet documented, the consequences of losing approximately 50% of population abundance are likely substantial and could result in local extinction of rare species, altered species interactions and social organization, as well as declining ecological function and biotic integrity of these tropical forest ecosystems.

Traits vary differently across a lowland forest–sand dune gradient in two common trees of the Amazon restinga coast

Intraspecific trait variation is a key feature that enables species to occur in heterogeneous landscapes. We studied Clusia grandiflora and Anacardium occidentale traits over a forest–dune gradient on the Brazilian Amazon coast (restinga). C. grandiflora showed a drought-avoidance strategy, storing water in its leaves, whereas A. occidentale showed conservative resource use in leaves, evidenced by its high dry-matter content and acquisitive resource in wood, showing lower wood density. Only A. occidentale changed its trait values through the forest–dune gradient, showing more conservative leaves in dunes and shrublands, despite a lower wood density than in forest. Leaf and wood traits are likely to be decoupled among Amazon coastal trees and their responses to environmental gradients are species-specific.

Tree Species–Soil Nutrients Association in Unlogged and Logged-over Tropical Forests, Sabah, Borneo

Natural forest cover in Sabah has been decreasing across all forest types for more than two decades since the 1990s, being replaced mostly by man-made forests. This contributes to the overall degradation of the forest ecosystem, which changes soil nutrient content and subsequently modifies forest species composition, as well as vegetation structure. This study investigated the association between soil nutrients and tree species in unlogged and logged tropical lowland forests in Sabah, Borneo, Malaysia. A total of eight and 27 sampling plots were established in randomly placed locations at the Danum Valley Conservation Area representing the unlogged site, as well as the Sapat Kalisun area of the Ulu Segama Forest Complex representing the logged site. Soil samples at two depths (0–5 cm; 5–10 cm) were collected from each plot and analyzed for soil nutrients: total N, available P, inorganic N (NO3 – and NH4 +), exchangeable cations (K+, Ca2+, Mg2+, and Na+), exchangeable Al3+, and exchangeable acidity. Results showed that certain exchangeable cations and soil nutrient concentrations were greater in the unlogged forest compared to the logged forest except for K+, Na+, and inorganic N. Greater inorganic N concentrations were observed in the logged forest, hence suggesting a dominant shift toward inorganic N in the soil. PCA results indicated that exchangeable acidity and exchangeable Al3+ were correlated to logged forests, whereas Ca2+ and Mg2+ were associated with unlogged forests. CCA ordination showed the existence of association between specific tree species with K+, Ca2+, Mg2+, and Na+ in the unlogged forest only. Logging, to some extent, influenced the status of certain soil nutrients but their association with tree species was complex. This could be attributed to the heterogeneous habitat resulting from past logging disturbances.

Ecological indicator values of understorey plants perform poorly to infer forest microclimate temperature

AbstractQuestionEcological indicator values (EIVs) reflect species‘ optimal conditions on an environmental gradient, such as temperature. Averaged over a community, they are used to quantify thermophilization stemming from climate change, i.e. the reshuffling of communities toward more warm‐adapted species. In forests, understorey plant communities do not keep up with global warming and accumulate a climatic debt. Although the causes are still debated, this thermal lag may be partly explained by forest microclimate buffering. For the first time, we test whether community means of EIVs are able to capture microclimate (here, under forest canopies) temperature across, or also within forests.Location157 forest plots across three French deciduous forests covering a large macroclimatic gradient.MethodsTo assess whether EIVs can be used to infer the mean and range of microclimate temperature in forests, we measured understorey air temperature for ca. 1 year (10 months) with sensors located 1 m above the ground. We surveyed bryophytes and vascular plants within 400‐m2 plots, and computed floristic temperature from ordinal‐scale EIVs (Ellenberg, Julve) and degree‐scale EIVs (ClimPlant, Bryophytes of Europe Traits) for both temperature and continentality, i.e. temperature annual range. Finally, we fitted linear models to assess whether EIVs could explain the mean and range of microclimate temperature in forests.ResultsVascular plant and bryophyte communities successfully reflected differences in mean annual temperatures across forests but largely failed to do so for microclimate variation within forests. Bryophytes did not perform better than vascular plants to infer microclimate conditions. The annual range of microclimate temperatures was poorly associated with ordinal‐scale EIVs for continentality but was positively correlated with degree‐scale EIVs for annual range within lowland forests, especially for vascular plant communities.ConclusionOverall, the capabilities of EIVs to infer microclimate was inconsistent. Refined EIVs for temperature are needed to capture forest microclimates experienced by understorey species.

Distribution, density and trends of the Eurasian eagle owl (Bubo bubo) population breeding in March-Thaya floodplain forests: impact of owlets on sustainability of natural nests

Abstract In this study, we investigated the Eurasian eagle owl (Bubo bubo) breeding in lowland forests in the trans-border area between western Slovakia, eastern Austria, and southern Moravia. The research provides new information on the reuse of nests by eagle owls and presents initial insights into population density and trends of eagle owls in the March-Thaya floodplains. Our 19-year monitoring has shown that the eagle owl has become a widespread breeder over the study area, with an increasing population trend. A total of 151 breeding attempts by eagle owls have been identified, occupying 82 natural nests (originally built by at least nine species of birds) and 12 artificial nests. With an average of 6.2 active nests per 100 km2 and a maximum of 17 active nests found in 2021 (~10.6 pairs per 100 km2), our findings represent one of the highest eagle owl breeding densities found, especially in comparison with core populations nesting in the mountains (the Carpathians, north-eastern Alps and the Bohemian Massif). Regarding the dynamics of nest reuse, our results reveal that only a third of nests used by eagle owls were reused by other raptors or storks (Ciconia sp.). Almost 50% of the natural nests in which eagle owl bred, subsequently disintegrated after the owlets had fledged. Lastly, black stork (Ciconia nigra) nests re-used by eagle owls were twice as likely to have disintegrated after the owlets had fledged than nests built by other bird species. Our results suggest that black stork nests in the March and Thaya floodplain forests are most susceptible to destruction.

Phylogenetic evidence reshapes the taxonomy of Cacao and its allies (Theobroma and Herrania; Malvaceae, Byttnerioideae)

Theobroma (Malvaceae, Byttnerioideae), the cacao genus, has a taxonomic history spanning over two centuries. Currently, it comprises 23 species of trees from lowland forests from the Tropical Americas. Herrania, a closely related genus described later, includes 17 additional species commonly referred to as “wild cacaos.” Phylogenetic relationships and morphological circumscriptions between Theobroma and Herrania have been the subject of debate. While Herrania has traditionally been treated as a separate genus based on evident morphological differences in leaf and petal features, it shares similarities with Theobroma in terms of habit, inflorescence, and fruit types. Recent phylogenetic evidence, incorporating a broader taxonomic sampling and a total-evidence analysis, suggested that Theobroma is paraphyletic, with Herrania nested within it. This finding supports the restoration of a classical circumscription of Theobroma wherein Herrania is considered a section of the former genus. Here, we provide a detailed account of the taxonomic history at infrageneric levels and propose one new subsection, two names at new ranks (to better allocate the diversity within T. sect. Herrania), and nine new combinations encompassing this expanded circumscription of Theobroma. In our study, we delimit Theobroma with forty species divided into six sections: T. sect. Glossopetalum (14 spp.), T. sect. Herrania (17 spp.), T. sect. Oreanthes (5 spp.), T. sect. Rhytidocarpus (1 sp.), T. sect. Telmatocarpus (2 spp.), and T. sect. Theobroma (1 sp.). Furthermore, we recognize three subsections within T. sect. Herrania. Alongside these newly proposed changes, we present a section-level identification key and provide diagnostic characters for each taxon.

Climbing aroids in a Panamanian lowland forest: We should reconsider our categories

AbstractBackgroundIn contrast to woody climbers, information on community composition or vertical extension within the forest is scarce for herbaceous climbers, even in well‐studied field sites like Barro Colorado Island. Moreover, questions regarding ontogenetic patterns (site of germination, changes in root/shoot connection with the soil) are unresolved because of a lack of field data.LocationBarro Colorado Island, Panama.MethodsIn 17 plots of 400 m2 each, which were distributed all over the island, we recorded all potential hosts (trees, palms, lianas) with a diameter at breast height larger than 1 cm, and all climbing aroids attached to them. For aroids, we recorded species identity, number of shoots, root connections to the ground, and vertical shoot extension. By distinguishing three size classes for each species in our analyses we deduced the site of germination and ontogenetic changes in the root/shoot connection with the soil.ResultsOnly 16% of all potential hosts were occupied by climbing aroids. We recorded 1196 individuals of 17 species. Aroids preferred larger trees and old‐growth forest. Species differed strongly in vertical distribution. Hemiepiphytic species germinate epiphytically, often high up in tree crowns and later establish root contact with the soil, while the majority of species establish on or close to the ground and reach moderate heights of 5–15 m (forest height ca. 35 m). In all of these species, we observed dieback of the proximal portion of the shoot to a varying extent but contact with the soil was invariably retained via adventitious roots.ConclusionsWe provide rare quantitative data on species richness and abundance of herbaceous climbers in a tropical lowland forest. Few species fall neatly into the categories of vines, nomadic vines and hemiepiphytes. This highlights the need for longitudinal observational and experimental studies to resolve the current debate on the appropriate grouping of these climbers.

No evidence of carbon storage usage for seed production in 18 dipterocarp masting species in a tropical rain forest.

Most canopy species in lowland tropical rain forests in Southeast Asia, represented by Dipterocarpaceae, undergo mast reproduction synchronously at community level during a general flowering event. Such events occur at irregular intervals of 2-10years. Some species do not necessarily participate in every synchronous mast reproduction, however. This may be due to a lack of carbohydrate resources in the trees for masting. We tested the hypothesis that interspecific differences in the time required to store assimilates in trees for seed production are due to the frequency of masting and/or seed size in each species. We examined the relationship between reproductive frequency and the carbon accumulation period necessary for seed production, and between the seed size and the period, using radiocarbon analysis in 18 dipterocarp canopy species. The mean carbon accumulation period was 0.84years before seed maturation in all species studied. The carbon accumulation period did not have any significant correlation with reproductive frequency or seed size, both of which varied widely across the species studied. Our results show that for seed production, dipterocarp masting species do not use carbon assimilates stored for a period between the masting years, but instead use recent photosynthates produced primarily in a masting year, regardless of the masting interval or seed size of each species. These findings suggest that storage of carbohydrate resources is not a limiting factor in the masting of dipterocarps, and that accumulation and allocation of other resources is important as a precondition for participation in general flowering.