Spatial pattern of trees in tropical lowland rain forest in Bawangling of Hainan Island,China
海南岛霸王岭热带低地雨林树木的空间格局

Aims Understanding processes underlying spatial distribution of tree species is fundamental to the study of spe-cies coexistence and diversity.Our objective was to determine the spatial structure and identify the processes that may generate spatial patterns of trees in a tropical lowland rain forest community on Hainan Island of South China.Methods Based on four models of point pattern analysis (homogenous Poisson process,inhomogenous Poisson process,homogenous Thomas process and inhomogenous Thomas process),we evaluated the potential contribu-tion of habitat heterogeneity and dispersal limitation to the formation of spatial patterns of tree species in two 1-hm2 stem-mapped forest dynamic plots.The relative importance of each process was assessed at six different spatial scales (< 2 m,2-5 m,5-10 m,10-15 m,15-20 m and 20-25 m).Important findings All stems combined revealed a strong aggregation at short distance (≤2 m),and the degree of aggregation decreased with increasing distance.Among the four models simulating tree distribution and pat-terning,the homogeneous Thomas process was the best-fit model.This result suggested that spatial patterns of tree species in tropical lowland rain forest might be formed by dispersal limitation.The homogeneous Poisson process that models the effect of spatial complete randomness was the second-best model.The inhomogeneous Thomas process and inhomogeneous Poisson process were equally important to forming spatial patterns of trees;they simulated the joint effects of habitat associations and dispersal limitation and modeled heterogeneity,respec-tively.The proportion of best-fit models differed across different scales.The dispersal limitation was a most im-portant mechanism in spatial patterning of tree species at most scales,while complete randomness process was second in importance.The joint effects of habitat associations and dispersal limitation mainly influenced tree dis-tribution at small scales (0-5 m).However,habitat heterogeneity only affected the distribution at larger scales (15-25 m).