亚热带常绿阔叶林种子性状对木本植物聚集格局的影响

Effect of seed traits on spatial aggregation of trees in a subtropical evergreen broad-leaved forest

种子的特征如种子的重量、大小和传播方式直接影响物种的扩散能力,从而影响物种空间分布的聚集强度。作者以古田山亚热带常绿阔叶林24 ha样地中89种木本植物为研究对象,分析了它们的种子大小、重量和扩散方式与物种聚集强度的关系。结果表明:在20 m范围内,样地内90%的物种为聚集分布,聚集强度随着尺度的增大而减弱,稀有种的聚集强度大于常见种。用系统发育独立比较(phylogenetically independent contrasts)方法排除了系统发育影响后,物种的多度与聚集强度呈显著相关(在15 m尺度,R2=0.32,P<0.001);种子大小与物种聚集强度的相关性较弱(R2=0.05,P<0.05),而种子重量与物种聚集强度之间的相关性相对较强(R2=0.14,P<0.05)。种子的传播方式显著地影响物种的聚集强度:无助力扩散物种的聚集强度显著地高于有助力扩散物种的聚集强度(F1,87=4.439,P=0.038),即长距离扩散导致物种的聚集强度减弱。可见,在亚热带森林中,种子性状通过影响种子扩散进而引起物种聚集强度的变化,是影响物种空间分布格局的重要生态因素。

The spatial distribution of species provides basic information for the study of species coexistence. Seed traits such as size, weight and dispersal syndromes influence the spatial distribution of species through various species-specific seed dispersal. In this study, we collected data on seed size, seed mass and seed dispersal syndromes of 89 woody trees in the Gutianshan subtropical evergreen broad-leaved forest. The relationship between seed size, seed mass, seed dispersal syndromes, and conspecific aggregation intensity were examined. Results showed that most of the species（-90%） were significantly aggregated across scales up to 20 m. The strength of spatial aggregation decreased with increasing spatial scales. Rare species were more aggregated than common species. Species abundance was significantly correlated with aggregation intensity（at spatial scale of 15 m, R2 = 0.32, P〈0.001） after removing the phylogenetic relationship among species using PIC（phylogenetically independent contrasts）. Seed size was weakly associated with aggregation intensity（R2 = 0.05, P〈0.05）, but seed mass was strongly correlated（R2 = 0.14, P〈0.05）. Seed dispersal syndromes significantly influenced species aggregation intensity： ballistically dispersed species were more significantly aggregated than assisted-dispersed species（F1, 87 = 4.439, P = 0.038）. Long-distances dispersal may lead to a reduction in aggregation intensity. In conclusion, species-specific seed traits and dispersal ability were ecologically significant factors impacting the spatial pattern of species distribution.