Scale dependence of species diversity pattern in a near-mature forest in Jiaohe of Jilin Province

Both habitat filtering and dispersal limitation are the key ecological processes affecting the structuring of community diversity pattern. The spatial scales at which different ecological processes work were determined in the structuring of species diversity pattern. The effect of 40 woody species on the local species richness was examined by individual species-area relationship model. The significance of deviation of individual species-area relationship from neutral condition was analyzed by homogeneous Poisson process, heterogeneous Poisson process, homogeneous Thomas process and heterogeneous Thomas process. The results revealed that Corylus mandshurica, Rhamnus davurica, Lonicera praeflorens, Acer ginnala and Fraxinus rhynchophylla were diversity accumulators at 0-50 m spatial scales. Tilia mandshurica at 0-25 m scale and Carpinus cordata at 0-35 m scale were diversity repellers, while most of other species were neutrals. The dispersal limitation greatly affected the structuring of community diversity pattern; however, the effect of habitat filtering was relative small. Heterogeneous Thomas model could simultaneously exclude the effects of habitat filtering and dispersal limitation. The results indicated that diversity accumulators were dominant at 0-20 m spatial scales in forest community. The proportion of diversity neutrals at scale 20 m increased with the increasing spatial scales, and the diversity neutrals dominated the structuring of the community diversity. Diversity repellers kept in a very low proportion at all scales. Thus, the niche differentiation and neutral processes jointly determined the structuring processes of community diversity, and the relative importance of both was closely correlated with the spatial scales.