Data from: Individual size variation reduces spatial variation in abundance of tree community assemblage, not of tree populations

Research on individual trait variation has gained much attention because of its implication for ecosystem functions and community ecology. The effect of individual variation on population and community abundance (number of individuals) variation remains scarcely tested. Using two established ecological scaling laws (Taylor's law and abundance–size relationship), we derived a new scaling relationship between the individual size variation and spatial variation of abundance. Tested against multi-plot tree data from Diaoluo Mountain tropical forest in Hainan, China, the new scaling relationship showed that individual size variation reduced the spatial variation of community assemblage abundance, but not of taxon-specific population abundance. The different responses of community and population to individual variation were reflected by the validity of the abundance–size relationship. We tested and confirmed this scaling framework using two measures of individual tree size: aboveground biomass and diameter at breast height. Using delta method and height-diameter allometry, we derived the analytic relation of scaling exponents estimated under different individual size measures. In addition, we used multiple regression models to analyze the effect of taxon richness on the relationship between individual size variation and spatial variation of population or community abundance, for taxon-specific and taxon-mixed data, respectively. This work offers empirical evidence and a scaling framework for the negative effect of individual trait variation on spatial variation of plant community. It has implications for forest ecosystem and management where the role of individual variation in regulating population or community spatial variation is important but understudied.

个体性状变异（individual trait variation）研究因其对生态系统功能与群落生态学的潜在价值，已受到学界广泛关注。目前，个体变异对种群与群落丰度（即个体数量）变异的影响仍鲜有实证验证。本研究依托两项成熟的生态缩放定律——泰勒定律（Taylor's law）与丰度-大小关系（abundance–size relationship），推导得到个体大小变异（individual size variation）与丰度空间变异之间的新型缩放关系。通过中国海南吊罗山热带森林的多样地树木数据开展验证后发现，个体大小变异会降低群落集合丰度的空间变异，但对类群特异性种群丰度的空间变异无显著调控效果。群落与种群对个体性状变异的差异化响应，可通过丰度-大小关系的有效性得以体现。我们采用地上生物量（aboveground biomass）与胸径（diameter at breast height）两种树木个体大小度量指标，对该缩放框架进行了检验与确认。借助德尔塔法（delta method）与树高-直径异速生长关系（height-diameter allometry），我们推导了不同个体大小度量方式下所估算的缩放指数的解析关联。此外，我们分别针对类群特异性数据与类群混合数据，构建多元回归模型，分析类群丰富度对个体大小变异与种群或群落丰度空间变异之间关系的调控作用。本研究为个体性状变异对植物群落空间变异的负向效应提供了实证依据与缩放分析框架，可为森林生态系统管理与保护提供重要参考——个体变异在调控种群或群落空间变异中扮演着关键角色，但目前相关研究仍较为匮乏。