Abstract:

Aims The relative influence of ecological factors on the distribution of woody plant functional types in a natural tropical forest landscape is rarely explored. The three major objectives of this study were to 1) determine the relative importance of environment, anthropogenic disturbance and spatial influences on the distribution of woody plant functional types, 2) determine which variables influence distribution of woody plant functional types, and 3) examine the distribution of woody plant functional types in different habitats.

Methods Using data from 135 plots in a natural tropical forest landscape of Hainan Island, South China, we classified woody plant functional types using the characteristics of species wood density and potential maximum height. Three sets were used, presence-absence, species richness and abundance. Their relations to environment, anthropogenic disturbance and spatial factors were analyzed with redundancy analysis (RDA). We then used a partial RDA with variation partitioning to specify which proportion of the variation in functional types distribution pattern is explained by each of the three factors individually and which proportion is attributable to interactions between factors.

Important findings We found that environmental influence, anthropogenic disturbance and interaction between environmental and anthropogenic disturbance factors were of similar importance in functional types distribution. However, spatial influence and interaction between spatial and other factors were less important. Furthermore, we found that anthropogenic disturbance types, topographical factors, soil types, grit content, soil depth and X, Y coordinates all impacted the distribution of functional types. Generally, hardwood functional types are abundant in better, undisturbed sites, but softwood functional types occur in opposite settings. The distributional range of medium hardwood functional types is wider than the other two. Except for softwood shrub functional types, the others have high species richness and abundance in better sites, especially where soils are deep. This study suggests that the plant functional type approach enhances understanding of the relative influence of environment, anthropogenic disturbance and spatial factors on species distribution. Environment and anthropogenic disturbance are more important than spatial influence in the variation of species distribution. These conclusions can aid in developing large-scale conservation and management policies in tropical rainforest areas.

Key words: woody plant functional types, spatial pattern, ecological factors, variation partitioning, RDA, tropical rain forest