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Effects of Environmental and Spatial Heterogeneity on Tree Community Assembly in Baotianman National Nature Reserve, Henan, China

ABSTRACT 
 The debate on species coexistence mechanisms never stops. The niche theory, neutral theory, and negative density dependence mechanism has been attracting considerable attention in recent years, but an integrated research on species coexistence mechanisms has rarely been conducted. In this study, a previous investigation at a plot in Henan Province was used as a basis to analyze the spatial structure of the community with principal coordinates of neighbor matrices (PCNM). Variance partitioning was used to analyze the effects of topography, soil, spatial, and stand density on species distribution. Results show that the community structure in the broad, medium, and fine scales generally showed a highly significant spatial structure. Topography, soil, spatial variables, and stand density explained 3.4, 11.7, 12.1 and 19.49% of species distribution, respectively. The aforementioned results suggest that spatial factor was an important factor that affects community structure. Species distribution was evidently influenced by environmental spatial heterogeneity. It had a very important function for density-dependent effects acting on species distribution. Niche theory, neutral theory, and negative density dependence mechanisms affected community building in different degrees.