Spatial distributions of intra-community tree species under topographically variable conditions.

Growing public awareness of the importance of protecting biodiversity requires the development of forest practices that increase the complexity of stand structure. Understanding the ecological processes of different forest vegetation provide insights into community coexistence mechanisms. In this paper, the spatial patterns of three different communities, evergreen broadleaf forest, deciduous broadleaf forest, and mixed needleleaf and broadleaf forest at Mt. Huangshan, China, were quantified with four structural parameters, the mingling index, the uniform angle index, the diameter dominance index and the crowdedness index. All trees with a diameter at breast height of more than 5 cm were measured. Our analyses highlighted that most trees in the three communities were extremely dense and slightly clumped, with a moderate size differentiation and high mixed structure. In mixed needleleaf and broadleaf forest, the distribution pattern of tree species was better than the other two forests. Overall, spatial patterns in mixed needleleaf and broadleaf forest exhibited a strong stability-effect, that is, the stand had a suitable environment for the stable survival of the forest. With the increasing of elevation, the degree of the mingling index and the crowdedness index increased, however, there was no influence on the uniform angle index and the diameter dominance index. Further, at the same elevation, four structural parameters of shady slope were larger than that of sunny slope. Then we found the relationship between stand spatial structure and environment factors had important influence on forest structure. Our work contributes to the knowledge of population structure, and further provide theoretical basis for the sustainable development of forest resources and protecting biodiversity of Huangshan Mountain. In future studies, it is necessary to explore the limiting factors of community spatial distribution by combining species diversity and functional traits. [ABSTRACT FROM AUTHOR]