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

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 such as size growth rate and mortality. 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.已有多项机制被提出，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。叶片分区理论（foliage partitioning theory）提出，由种间死亡率-生长比差异所引发的垂直叶片分布分化，可促进物种的稳定共存。与之相对，演替生态位理论（successional niche theory）则认为，由林隙动态驱动的水平光照异质性，会通过物种在生长速率与存活之间的种间权衡关系，增强物种共存能力。为区分这些物种共存理论，我们对马来西亚巴沙河森林保护区（Pasoh Forest Reserve）内50公顷样地中370个物种的树木清查数据开展了分析。我们采用群落级贝叶斯模型（Bayesian models）量化了每一物种的体型依赖型生长速率与死亡率。我们将观测得到的体型分布与基于体型依赖型种群统计速率得到的预测分布进行了对比。研究结果表明，观测到的体型分布并非仅与种群增长率相关，而是与体型生长速率、死亡率等种群统计特性紧密关联。在体型分布中幼树相对丰度较低的物种，在小树阶段呈现出高生长速率与低死亡率的特征，且其单位个体补充率较低。总体而言，我们的研究发现与叶片分区理论的预测结果相一致。