Abstract:

Aims Phylogenetic structure of a community is a synthetical indicator reflecting underlying ecological processes. Understanding of the phylogenetic structure of a community will provide insights into the relative importance of different processes structuring the community. Our objectives are 1) examine the effects of environmental factors on phylogenetic structure; 2) test the prediction of neutral theory that the community is randomly assembled and the prediction of niche theory that the community is mainly determined by niche differentiation; and 3) determine the relative importance of neutral theory and niche theory in biodiversity maintenance in subtropical evergreen broadleaved forest.

Methods Gutianshan forest dynamic plot is located in the Gutianshan National Nature Reserve at Kaihua County, Zhejian Province of China. We randomly chose 1 000 subplots at five spatial scales of radii 5, 25, 50, 75 and 100 m in the Gutianshan forest dynamic plot and analyzed phylogenetic structure of subplots at these scales with net relatedness index (NRI). We analyzed the effect of environmental factors, including topographical factors, such as altitude, slope, aspect and convexity, and edaphic factors such as soil moisture, pH and 16 soil nutrients, on the community phylogenetic structure with multivariate regression.

Important findings Communities were phylogenetically clustered at all spatial scales, indicating that trees were more closely related to their neighbors than expected by chance. With increasing scale, the strength of clustering increased and then deceased. Multiple linear regression showed that environmental factors had almost no effect on phylogenetic structure at smaller scales, but strongly affected the community structure at larger scales (radius of 100 m). At the radius of 100 m, two types of different phylogenetic structure emerged: some of subplots kept clustering, yet others became overdispersed. The difference of phylogenetic community structures at scale of 100 m was mainly determined by altitude. Our results support the prediction of niche theory that the community phylogenetic structure is structured by niche differentiation, and do not support the prediction that the community phylogenetic structure is randomly assembled by ecological drift and dispersal limitation.

Key words: environmental factors, forest dynamics plot, phylogenetic structure, spatial scale