Data from: Demographic properties shape tree size distribution in a Malaysian rainforest

Different mechanisms have been proposed to explain how vertical and horizontal heterogeneity in light conditions enhances tree species coexistence in forest ecosystems. The foliage partitioning theory proposes that differentiation in vertical foliage distribution, caused by an interspecific variation in mortality-to-growth ratio, promotes stable coexistence. In contrast, successional niche theory posits that horizontal light heterogeneity, caused by gap dynamics, enhances species coexistence through an interspecific trade-off between growth rate and survival. To distinguish between these theories of species coexistence, we analyzed tree inventory data for 370 species from the 50-ha plot in Pasoh Forest Reserve, Malaysia. We used community-wide Bayesian models to quantify size-dependent growth rate and mortality of every species. We compared the observed size distributions and the projected distributions from size-dependent demographic rates. We found that the observed size distributions were not simply correlated with the rate of population increase, but were related to demographic properties. Species with low relative abundance of juveniles in size distribution showed high growth rate and low mortality at small tree sizes, and low per-capita recruitment rate. Overall our findings were in accordance with those predicted by foliage partitioning theory.已有多项研究提出不同机制，用以阐释森林生态系统中光照条件的垂直与水平异质性如何促进树木物种共存。叶片分层理论（Foliage Partitioning Theory）提出，因物种间死亡率-生长比的种间差异所导致的垂直叶片分布分化，可促进物种稳定共存。与之相对，演替生态位理论（Successional Niche Theory）则认为，由林隙动态引发的水平光照异质性，可通过物种间生长速率与存活能力的权衡关系增强物种共存。为区分这两种物种共存理论，我们分析了马来西亚巴沙森林保护区（Pasoh Forest Reserve）50公顷样地内370个树种的树木清查数据。我们采用群落级贝叶斯模型（Bayesian models）量化了各物种的大小依赖型生长速率与死亡率。将观测得到的种群大小分布与基于大小依赖型种群统计速率得到的预测分布进行对比后发现，观测到的种群大小分布并非仅与种群增长率相关，而是与种群统计特征紧密关联。在种群大小分布中幼树相对丰度较低的物种，在小树阶段表现出较高的生长速率与较低的死亡率，且其单位个体补充率偏低。综合来看，我们的研究结果与叶片分层理论的预测相符。