Effects Of Large-scale Species Abundance Distribution Pattern And Environmental Heterogeneity On Local Community Structure Under Different Assembly Mechanisms

To understand the mechanism of maintenance of species diversity is a central goal of ecology.In the studies of focusing on local community dynamics,it is often assumed that large-scale species abundance distribution fits one kind of patterns,such as uniform or log-normal distribution.However,it has not been proved which pattern the natural community is more accordance.To study this problem,we consider four types of community structure models: uniform species pool and logarithmic normal species pool combined with neutral model and niche-neutral continuum model,respectively.We also analyzed the effects of environmental heterogeneity on local community structure under niche partitioning and neutrality mechanism.We applied an individual-based spatially explicit model to predict the community structure under different mechanism,and investigated the species diversity in the alpine meadows of the Tibetan Plateau on different slope aspect(south,southwest,west,northwest,north)to verify the results of the model.By combining simulation results of the model and field investigation,our results show that: 1)only in niche-neutral community linked to log-normal species pool,the species abundance distribution fits to logarithmic series distribution,other combinations fit to log-normal distribution.The field data shows that the species abundance distribution pattern is consistence with logarithmic series distribution.2)Based on the similarity analysis between dominant species and the whole community,we found that the similarity between niche-neutral community linked to log-normal species pool are more closed with field investigation.3)In simulation,the species abundance distribution in different habitat fits to the logarithmic series distribution.Field investigation shows that the species abundance distribution pattern accords with logarithmic series distribution in all slopes except the south slope on which and species abundance distribution fits to logarithmic normal distribution.4)The simulation results show that the species diversity of communities increased with environmental heterogeneity.The field surveys show that the species diversity of local community increases from south slopes to north slopes.5)The simulation results show that the similarity of community composition decreased when the environmental condition is more heterogeneous,the similarity between communities of the south slope to the communities along south to north decreased in the field.Conclusion: in subalpine meadow,local community plant diversity is maintained by combining niche and neutral dynamics,and the species abundance distribution pattern of pool is log-normal.There is a significant difference in species diversity and composition of plant communities with different slope aspects,main reason is the environmental heterogeneity increased with the slope aspects from south slope facing to north slope facing.