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.学界已提出多种机制，用以解析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：由物种间死亡率与生长率之比的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，演替生态位理论则认为：由林隙动态引发的水平光照异质性，可通过种间生长率与存活能力的权衡关系提升物种共存水平。为区分这两种物种共存理论，我们分析了采自马来西亚巴沙河森林保护区（Pasoh Forest Reserve）50公顷样地（50-ha plot）的370个物种的树木清查数据。我们采用群落尺度贝叶斯模型（community-wide Bayesian models），量化了各物种的个体大小依赖的生长率与死亡率。我们将实测的个体大小分布，与基于个体大小依赖的种群动态参数预测得到的分布进行了对比。研究发现，实测的个体大小分布并非仅与种群增长率相关，而是与个体大小生长率、死亡率等种群动态特征密切相关。在个体大小分布中幼树相对丰度较低的物种，在小型树阶段表现出较高的生长率与较低的死亡率，且单株补充率较低。总体而言，本研究结果与叶片分区理论的预测相符。