Tropical Seasonal Rain Forest Research Articles

Quantifying regional vegetation changes in China during three contrasting temperature intervals since the last glacial maximum

The need to reduce the uncertainty of predictions of vegetation change under global warming highlights the importance of understanding the vegetation patterns and possible mechanisms of vegetation response during past warming intervals. Here, we present quantitative regional vegetation reconstructions for China during the Last Glacial Maximum (LGM, 18 ± 2 14C kyr B.P.), early Holocene (EH, 8.5 ± 0.5 14C kyr B.P.), and mid-Holocene (MH, 6 ± 0.5 14C kyr B.P.), using the biomization method and based on 249 pollen records. In addition, we used an inverse vegetation modeling approach to investigate the effect of climate change and CO2 concentration on the observed vegetation changes. The results demonstrate that during the LGM, steppe expanded southeastwards, reaching the present-day temperate deciduous forest (TEDE) zone; in contrast, the forest in eastern China underwent a substantial southward retreat and its percentage reached a minimum. The warm mixed forest (WAMF) and TEDE shifted southwards of ∼10° N relative to today, and tropical seasonal rain forest (TSFO) was almost absent. In addition, the forest-steppe boundary shifted southwards to near the middle and lower reaches of the Yangtze River. During the EH and MH, the TSFO, WAMF, and TEDE exhibited respective northward shifts of 2°, 4° and 5° relative to today. In MH, the percentage of forest sites increased and reached a maximum, and the forest-steppe boundary had shifted northwestwards to near the present-day 300 mm isohyet. Our palaeovegetation reconstructions and model sensitivity experiments suggest that temperature was the dominant factor controlling the vegetation distribution during the LGM, while precipitation became increasingly more important during the Holocene throughout China. We further show that precipitation was the primary factor controlling palaeovegetation distribution in northern China, while temperature became increasingly more important in southern China. Our findings are potentially important for understanding the evolution of vegetation in China in response to ongoing global warming.

Does Wood Fuel Gathering for Household Use Follow an Optimality Model? A Study from Kakamega Forest, Western Kenya

Successful management of forests, especially in the context of subsistence wood fuel use, can be improved by the application of theoretic models that predict patterns of use. A first step in this approach is understanding the decision rules of people using forests. While optimal foraging theory is normally applied to foraging for food, it also makes sense to apply it in the context of “foraging” for wood fuel. In this study, we applied a time allocation model of optimal foraging theory to wood gathering decisions in communities around Kakamega Forest, a mid-altitude seasonal tropical rain forest. The model predicts that the amount of wood gathered should increase with the distance to the wood source. We found that the predictions of OFT are supported, but only for adults and more strongly on a weekly scale. Based upon the results, we then discuss future improvements of the model to better understand and predict human use.

Effects of forest transition on litterfall, standing litter and related nutrient returns: Implications for forest management in tropical China

Land-use change is widespread throughout the tropics where large areas of natural forests being converted to secondary forests and tree plantations. In order to search for appropriate forest management, it is necessary to evaluate litter production, its temporal variation, and nutrient return of these ecosystems. In this study therefore, we investigated litterfall production, standing litter and litter quality for 5 years in a tropical seasonal rainforest (TSR), tropical secondary forest (TSF), tropical anthropogenic forest (TAF), and a rubber monoculture (RM) in Xishuangbanna, SW China. Results showed that the annual mean litterfall was significantly higher in TSF (14.83 Mg ha−1 year−1), followed by TAF (12.69 Mg ha−1 year−1), TSR (11.20 Mg ha−1 year−1) and RM (9.21 Mg ha−1 year−1). Both precipitation and temperature exerted greater impacts on litterfall amount in TSR and TSF than that in TAF and RM. The peak litterfall occurred in the cool and dry season for all four forest sites. Average standing litter for 5 years followed the order of TAF (3.08 Mg ha−1) > RM (2.91 Mg ha−1) > TSR (2.52 Mg ha−1) > TSF (2.04 Mg ha−1). Total returns of C, N, P, and K to mineral soil showed a decreasing trend of TSF > TAF > TSR > RM, which had a variation pattern similar to that for litter production. Nutrient-use efficiency varied with the mineral elements involved, and they differed significantly across the four forest types. Overall, litter production and nutrient returns increased after conversion of tropical primary forest to secondary forest and anthropogenic forest, but both responses decreased after conversion to the rubber monoculture. Therefore, establishing a multilayered community on degraded tropical land or introducing native species into ageing rubber forest offers a promising way to maintain the sustainable use and management of local forest resources.

Flowering and Fruiting Phenology of Woody Trees in the Tropical-Seasonal Rainforest, Southwestern China

The reproductive phenology of tropical plants is potentially driven by a number of abiotic and biotic factors. However, it is still unclear as to which climatic factors and biotic interactions drive the reproductive phenology of woody trees in the tropical seasonal rainforest of Xishuangbanna region in Southwest China. We conducted observations on woody plants (including trees and shrubs) phenology between November 2004 and October 2007 at bi-weekly intervals in the one hectare permanent plot of tropical seasonal rainforest in Southwest China. A total of 357 individuals of 76 species (70 genera, 37 families),comprising of 59 (78%) woody trees and 17(22%) shrub species were observed. Our results demonstrate that flowering an fruiting frequencies show slight temporal variation between years. Flowering was significantly correlated with day-length, temperature and rainfall and fruiting was significantly correlated with rainfall and temperature. This finding indicates that woody tree reproductive phenology was primarily associated with temperature and rainfall and to a lesser extent with day-length. Reproductive phenology is also linked to seasonal patterns with flowering peaking in the late dry season and fruiting peaking in the late wet season. Moreover, reproductive phenology is also significantly associated with reproductive ecological guilds such as pollination types and dispersal modes. Community reproductive phenology is associated with climatic seasonality and biotic interactions. It also suggests that seasonal phenology patterns may play a fundamental role in community reproductive success in the tropical seasonal rainforest of Xishuangbanna region of South-west China.

Asplenium cyrtosorum (Aspleniaceae), a new fern from Yunnan, China

A new species, Asplenium cyrtosorum, is described and illustrated from Pu’er, southwestern Yunnan, China. It was observed to grow in humid and shady conditions in the tropical seasonal rainforest. The new species differs from the morphologically most similar species A. trapezoideum by its shape of rhizome, length of rhizome scales, structure of laminae, pinna pairs and rachis structure.

Seed dormancy-life form profile for 358 species from the Xishuangbanna seasonal tropical rainforest, Yunnan Province, China compared to world database

Seed dormancy profiles are available for the major vegetation regions/types on earth. These were constructed using a composite of data from locations within each region. Furthermore, the proportion of species with nondormant (ND) seeds and the five classes of dormancy is available for each life form in each region. Using these data, we asked: will the results be the same if many species from a specific area as opposed to data compiled from many locationsare considered? Germination was tested for fresh seeds of 358 species in 95 families from the Xishuangbanna seasonal tropical rainforest (XSTRF): 177 trees, 66 shrubs, 57 vines and 58 herbs. Seeds of 12.3% of the species were ND, and 0.3, 14.8, 60.6, 12.0 and 0% of the species had morphological (MD), morphophysiological (MPD), physiological (PD), physical (PY), and combinational (PY + PD) dormancy, respectively. PD was more important than ND in all life forms, PY was highest in shrubs, MD was not important in any life form and MPD was most common for herb and vines. The seed dormancy profile for XSTRF differs considerably from the composite profile for this vegetation type worldwide, most obviously in ND being much lower and PD much higher in XSTRF.

Seed Germination Requirements of Ficus virens (Moraceae) as Adaptation to Its Hemi-Epiphyte Life Form

Epiphytes and hemi-epiphytes are important floristic, structural and functional components of tropical rainforests. Their specific responses to light, temperature and water conditions during seed germination allow them to coexist with tropical forest trees. Here we investigated the effects of temperature, red to far-red light ratio (R:FR ratio) and water stress on seed germination of Ficus virens in tropical seasonal rainforest in Southwest China. We used incubators to create required temperature regimes, polyester filters to produce R:FR ratio gradients and mannitol solutions to simulate water stress. It was found that seed germination of F. virens was inhibited in the simulated understory conditions, i.e., at lower temperature (22/23°C), especially when combined with the R:FR ratio of 0.25, for which the germination percentage was less than 20%. In contrast, the seed germination percentages in the simulated canopy environment (22/32°C) showed no significant difference between R:FR ratios, with an average seed germination percentage as high as 65.8%. Seed germination delayed and decreased along with increasing water stress and was completely inhibited at -2.5 MPa, which might suggest that it is a kind of adaptation for F. virens seeds to detect the rainy season as germination chance on the canopy. Therefore, our study revealed the physiological mechanism for F. virens to be able to adapt to canopy environment.

Transition from abstract thermodynamic concepts to perceivable ecological indicators

Entropy and exergy are the central concepts in thermodynamics, and many researchers have used them to characterize ecosystem development. However, these concepts are very abstract to outsiders. Direct measurements of the indicators related to entropy and exergy are difficult and involve large errors. Schneider and Kay (1994) bridged thermodynamic concepts, i.e., entropy and exergy, with perceivable ecological indicators, i.e., canopy surface temperature (Tsurf) and net radiation (Rn) in their maximum exergy destruction principle. However, the connection between entropy and exergy with Tsurf and Rn was based on the similarity between the ecosystem and the Bénard cell, and not on thermodynamic reasoning. Considering the coherence of entropy production and exergy destruction, we analyzed the relationship between entropy production and Tsurf and Rn, based on the first and second laws of thermodynamics, and verified it using long-term monitoring data of a tropical seasonal rain forest. We demonstrated that total entropy production (exergy destruction) linearly increased with increasing Rn and decreasing Tsurf theoretically. Empirical data showed that the total entropy production increased, whereas specific entropy production decreased during the growing season. This indicates that plant growth can enhance exergy conversion efficiency. Rn, Tsurf, and related indicators can be used as surrogates for thermodynamic indicators to measure ecosystem status and development. The bridge between thermodynamic concepts and measurable ecological indicators will improve the application of thermodynamics in ecology studies and the understanding of thermodynamic processes in ecosystem.

Impact of tropical forest conversion on soil bacterial diversity in tropical region of China

In Xishuangbanna, a China's tropical region, monoculture rubber plantations have expanded dramatically over the past two decades. However, the effect of conversion of tropical forests to rubber plantations on the soil microbial compositions and diversity remains poorly understood. This study investigated the bacterial diversity and biomass in rubber plantations, secondary tropical forest and tropical seasonal rainforest in Xishuangbanna, southwest China, based on an analyses of PCR-amplified 16S rRNA genes. Our findings revealed that soil of rubber plantation was different from secondary tropical forest and tropical seasonal rainforest in bacterial compositions at phylum, family as well as OTU (Operational Taxonomic Units) levels. The most abundant phylum in rubber plantations was Firmicutes, however, in secondary tropical forest and tropical seasonal rainforest it was Proteobacteria. In both dry season and rainy season, diversity indices of rubber plantations were significantly higher than those of secondary tropical forest and tropical seasonal rainforest, indicating that bacterial diversity increased after conversion. However, the total microbial biomass carbon (MBC) decreased after conversion. RDA results showed that soil pH and total phosphorus maybe the two most important factors controlling bacterial communities, and explained 49.2% and 38.1% of total variance of phylum compositions, respectively. Management practices, especially the application of fertilizers with phosphorous would thus probably influence the taxonomic composition and diversity of bacterial communities in this region.

Lack of phylogenetic signals within environmental niches of tropical tree species across life stages

The lasting imprint of phylogenetic history on current day ecological patterns has long intrigued biologists. Over the past decade ecologists have increasingly sought to quantify phylogenetic signals in environmental niche preferences and, especially, traits to help uncover the mechanisms driving plant community assembly. However, relatively little is known about how phylogenetic patterns in environmental niches and traits compare, leaving significant uncertainty about the ecological implications of trait-based analyses. We examined phylogenetic signals within known environmental niches of 64 species, at seedling and adult life stages, in a Chinese tropical forest, to test whether local environmental niches had consistent relationships with phylogenies. Our analyses show that local environmental niches are highly phylogenetically labile for both seedlings and adult trees, with closely related species occupying niches that are no more similar than expected by random chance. These findings contrast with previous trait-based studies in the same forest, suggesting that phylogenetic signals in traits might not a reliable guide to niche preferences or, therefore, to community assembly processes in some ecosystems, like the tropical seasonal rainforest in this study.

Diversity and assemblage structure of bark‐dwelling spiders in tropical rainforest and plantations under different management intensities in Xishuangbanna, China

Abstract In tropical Southeast Asia, large‐scale establishment of forest plantations has reduced forest diversity and altered arthropod assemblages by changing plant communities and ecological properties. Few studies address the impacts of forest change on important predatory groups on tree trunks. We compared spider assemblages on tree trunks in natural forests and three forest plantation types in the Xishuangbanna area of southwestern China, to determine how tropical forest management influences bark‐dwelling spider composition. Spiders were sampled using trunk traps in tropical seasonal rain forests (TSRF), rubber plantations (RP), rubber‐tea mixtures (RTM) and Aporosa yunnanensis plantations (AYP). Spider species composition differed between TSRF and forest plantations. Canopy cover in both seasons and grass cover and shrub cover in the dry season well explained species assemblages. Spider diversity between TSRF and forest plantations differed more distinctly in the rainy season. AYP had an intermediate level of disturbance, which was associated with highest species richness, whereas TSRF had the highest beta diversity. The mean number of individuals was the highest in RP, but species richness and beta diversity were the lowest. An intermediate level of disturbance increased alpha diversity of bark‐dwelling spiders, whereas intensive management that altered vegetation structure had adverse effects on these spiders. Preservation or enhancement of surface vegetation in RP may maintain or increase species richness of bark‐dwelling spiders. The highest beta diversity of the TSRF indicated that undisturbed natural forests better conserved regional spider diversity than plantations.

Change in Soil Microbial Community Compositions and Diversity Following the Conversion of Tropical Forest to Rubber Plantations in Xishuangbanan, Southwest China

The ecological consequences of converting tropical forests to rubber plantations on the soil microbial compositions and diversity remain unknown. By using an Illumina MiSeq sequencing analysis, we assessed the compositions and diversity of bacterial and fungal community in soils of rubber plantation (or rubber forest, RF), secondary tropical forest (STF), and tropical seasonal rainforest (TSR) in Xishuangbanna, southwest China. Our findings revealed that (a) for bacterial composition, Bacillaceae was the most dominant family (13.60%) in RF soil, while it only accounted for 4.13% in STF and 6.92% in TSR. For fungal composition, the largest family in soils of RF was Basidiomycota_unclassified. However, the largest family in STF and TSR was Russulaceae. (b) Number of operational taxonomic units, Chao index, and Shannon index of bacterial community in soil of RF were significantly higher than those of TSR and STF. However, these diversity indices of fungal community in RF were significantly lower than those o...

Coarse woody decay rates vary by physical position in tropical seasonal rainforests of SW China

Decomposition of woody detritus is an important but often ignored process in forest ecosystems. Moisture and temperature regimes are dominant controls over woody decay, contributing to significant variability at local, regional, and global scales. Our focus was on local variability in woody decay rates depending on their physical position. Woody detritus may decay on the forest floor, aboveground, or combination of both, depending on the mortality agent. In this study, we measured decay rates of logs, large branches on the forest floor, and snags over a three-year period. We also collected monthly respiration estimates, and analyzed woody detritus N and P content throughout the study. Logs exhibited the greatest mass loss with a decay-rate constant of k=0.606±0.020, followed by large branches (k=0.316±0.012) and snags (k=0.268±0.008). Heterotrophic respiration was greatest prior to the peak of rainy season, and was greatest for snag material during the first two years of sampling, probably a result of water saturation in ground material. Both N and P were released in all materials, but the rate of P release was much slower in snags. There were large differences of P concentration and C:P among the materials, but their value became similar after three years, indicating P limitation on microbial activities. Our results presented robust evidence for the physical-position-dependence of coarse woody detritus decomposition in the forests.

Soil phosphorus heterogeneity promotes tree species diversity and phylogenetic clustering in a tropical seasonal rainforest.

The niche theory predicts that environmental heterogeneity and species diversity are positively correlated in tropical forests, whereas the neutral theory suggests that stochastic processes are more important in determining species diversity. This study sought to investigate the effects of soil nutrient (nitrogen and phosphorus) heterogeneity on tree species diversity in the Xishuangbanna tropical seasonal rainforest in southwestern China. Thirty‐nine plots of 400 m2 (20 × 20 m) were randomly located in the Xishuangbanna tropical seasonal rainforest. Within each plot, soil nutrient (nitrogen and phosphorus) availability and heterogeneity, tree species diversity, and community phylogenetic structure were measured. Soil phosphorus heterogeneity and tree species diversity in each plot were positively correlated, while phosphorus availability and tree species diversity were not. The trees in plots with low soil phosphorus heterogeneity were phylogenetically overdispersed, while the phylogenetic structure of trees within the plots became clustered as heterogeneity increased. Neither nitrogen availability nor its heterogeneity was correlated to tree species diversity or the phylogenetic structure of trees within the plots. The interspecific competition in the forest plots with low soil phosphorus heterogeneity could lead to an overdispersed community. However, as heterogeneity increase, more closely related species may be able to coexist together and lead to a clustered community. Our results indicate that soil phosphorus heterogeneity significantly affects tree diversity in the Xishuangbanna tropical seasonal rainforest, suggesting that deterministic processes are dominant in this tropical forest assembly.

Rainforests north of the Tropic of Cancer: Physiognomy, floristics and diversity in ‘lowland rainforests’ of Meghalaya, India

The lowland rainforests of Meghalaya, India represent the westernmost limit of the rainforests north of the Tropic of Cancer. These forests, on the Shillong plateau, are akin to Whitmore's ‘tropical lowland evergreen rainforest’ formation and exhibit striking similarities and conspicuous differences with the equatorial rainforests in Asia-Pacific as well as tropical seasonal rainforests in southwestern China near the Tropic of Cancer. We found these common attributes of the rainforests in Meghalaya: familial composition with predominance of Euphorbiaceae, Lauraceae, Meliaceae, Moraceae, Myrsiticaceae, Myrtaceae and Rubiaceae; deciduousness in evergreen physiognomy; dominance of mega- and mesophanerophytic life-forms; abundance of species with low frequency of occurrence (rare and aggregated species); low proportional abundance of the abundant species; and truncated lognormal abundance distribution. The levels of stand density and stand basal area were comparable with seasonal rainforests in southwestern China, but were lower than equatorial rainforests. Tropical Asian species predominated flora, commanding 95% of the abundance. The differences include overall low stature (height) of the forest, inconspicuous stratification in canopy, fewer species and individuals of liana, thicker understory, higher proportion of rare species, absence of locally endemic species and relatively greater dominance of Fagaceae and Theaceae. The richness of species per hectare (S) was considerably lower at higher latitudes in Meghalaya than in equatorial rainforests, but was comparable with seasonal rainforests. Shannon's diversity index (H′ = 4.40 nats for ≥10 cm gbh and 4.25 nats for ≥30 cm gbh) was lower on higher latitudes in Meghalaya in comparison to species-rich equatorial rainforests, but it was the highest among all lowland rainforests near the Tropic of Cancer.

Factors controlling bark decomposition and its role in wood decomposition in five tropical tree species.

Organic matter decomposition represents a vital ecosystem process by which nutrients are made available for plant uptake and is a major flux in the global carbon cycle. Previous studies have investigated decomposition of different plant parts, but few considered bark decomposition or its role in decomposition of wood. However, bark can comprise a large fraction of tree biomass. We used a common litter-bed approach to investigate factors affecting bark decomposition and its role in wood decomposition for five tree species in a secondary seasonal tropical rain forest in SW China. For bark, we implemented a litter bag experiment over 12 mo, using different mesh sizes to investigate effects of litter meso- and macro-fauna. For wood, we compared the decomposition of branches with and without bark over 24 mo. Bark in coarse mesh bags decomposed 1.11–1.76 times faster than bark in fine mesh bags. For wood decomposition, responses to bark removal were species dependent. Three species with slow wood decomposition rates showed significant negative effects of bark-removal, but there was no significant effect in the other two species. Future research should also separately examine bark and wood decomposition, and consider bark-removal experiments to better understand roles of bark in wood decomposition.

Elevational Distribution of Adult Trees and Seedlings in a Tropical Montane Transect, Southwest China

Montane habitats are characterized by high variation of environmental factors within small geographic ranges, which offers opportunities to explore how forest assemblages respond to changes in environmental conditions. Understanding the distributional transition of adult trees and seedlings will provide insight into the fate of forest biodiversity in response to future climate change. We investigated the elevational distribution of 156 species of adult trees and 152 species of seedlings in a tropical montane forest in Xishuangbanna, southwest China. Adult trees and seedlings were surveyed within 5 replicate plots established at each of 4 elevational bands (800, 1000, 1200, and 1400 m above sea level). We found that species richness of both adult trees and seedlings changed with elevation, showing a notable decline in diversity values from 1000 to 1200 m. Tree species composition also demonstrated distinct differences between 1000 and 1200 m, marking the division between tropical seasonal rain forest (800 ...

Species associations of congeneric species in a tropical seasonal rain forest of China

Abstract:In tropical plant communities with diverse species, many congeners are found to coexist. Do environment or biotic interactions structure the coexistence of congeners in tropical forest communities? In this paper, we aimed to disentangle the effect of environment (first-order effects) and species interactions (second-order effects) on the spatial distributions of tree species. We used a classification scheme and torus-translation to test the first-order interaction of 48 species from 17 genera in a fully mapped 20-ha dipterocarp tropical seasonal rain-forest plot in Xishuangbanna, south-west China. Then we used heterogeneous Poisson null models to reveal significant uni- and bivariate second-order interactions. The results demonstrated that (1) 34 of the 48 studied species showed a significant relation with at least one topographic variable. This confirmed that topographical heterogeneity is important for distribution of these congeners. Spatial segregation (36.6%) and partial overlap (34.8%) were the most common bivariate association types in Xishuangbanna plot, which indicated first-order effects (environment) were strong. (2) For small-scale associations, 51% saplings (1 to ≤ 5 cm) (68.8% for large trees with dbh > 5 cm) of the species showed non-significant associations. For large-scale associations, 61.6% saplings (81.2% for large trees) of the species showed non-significant associations. Lack of significant species interactions provides evidence for the unified neutral theory. In conclusion, both environment and biotic interactions structure congeneric species' coexistence in tropical seasonal rain forest in this region.

Soil properties drive a negative correlation between species diversity and genetic diversity in a tropical seasonal rainforest.

A negative species-genetic diversity correlation (SGDC) could be predicted by the niche variation hypothesis, whereby an increase in species diversity within community reduces the genetic diversity of the co-occurring species because of the reduction in average niche breadth; alternatively, competition could reduce effective population size and therefore genetic diversity of the species within community. We tested these predictions within a 20 ha tropical forest dynamics plot (FDP) in the Xishuangbanna tropical seasonal rainforest. We established 15 plots within the FDP and investigated the soil properties, tree diversity, and genetic diversity of a common tree species Beilschmiedia roxburghiana within each plot. We observed a significant negative correlation between tree diversity and the genetic diversity of B. roxburghiana within the communities. Using structural equation modeling, we further determined that the inter-plot environmental characteristics (soil pH and phosphorus availability) directly affected tree diversity and that the tree diversity within the community determined the genetic diversity of B. roxburghiana. Increased soil pH and phosphorus availability might promote the coexistence of more tree species within community and reduce genetic diversity of B. roxburghiana for the reduced average niche breadth; alternatively, competition could reduce effective population size and therefore genetic diversity of B. roxburghiana within community.

Drought tolerance as a driver of tropical forest assembly: resolving spatial signatures for multiple processes.

Spatial patterns in trait variation reflect underlying community assembly processes, allowing us to test hypotheses about their trait and environmental drivers by identifying the strongest correlates of characteristic spatial patterns. For 43 evergreen tree species (> 1 cm dbh) in a 20-ha seasonal tropical rainforest plot in Xishuangbanna, China, we compared the ability of drought-tolerance traits, other physiological traits, and commonly measured functional traits to predict the spatial patterns expected from the assembly processes of habitat associations, niche-overlap-based competition, and hierarchical competition. We distinguished the neighborhood-scale (0-20 m) patterns expected from competition from larger-scale habitat associations with a wavelet method. Species' drought tolerance and habitat variables related to soil water supply were strong drivers of habitat associations, and drought tolerance showed a significant spatial signal for influencing competition. Overall, the traits most strongly associated with habitat, as quantified using multivariate models, were leaf density, leaf turgor loss point (π(tlp); also known as the leaf wilting point), and stem hydraulic conductivity (r2 range for the best fit models = 0.27-0.36). At neighborhood scales, species spatial associations were positively correlated with similarity in π(tlp), consistent with predictions for hierarchical competition. Although the correlation between π(tlp) and interspecific spatial associations was weak (r2 < 0.01), this showed a persistent influence of drought tolerance on neighborhood interactions and community assembly. Quantifying the full impact of traits on competitive interactions in forests may require incorporating plasticity among individuals within species, especially among specific life stages, and moving beyond individual traits to integrate the impact of multiple traits on whole-plant performance and resource demand.