Intraspecific Trait Variation Promoting Plant Community Assemblage in a Tropical Cloud Forest

Abstract

Trait-based approaches have been recognized as an effective way to understand the ecological process of structuring plant communities. Despite plant traits found to vary both between and within species, most previous studies of trait-based community assembly were tested with species mean trait values and seldom accounted for intraspecific trait variation (ITV). We measured five functional traits for 14,499 tree individuals and constructed species pools according to 217 species surveyed from three tropical cloud forests in Hainan island. Then we calculated Rao quadratic entropy index (RaoQ) and community weighted mean value (CWM) using species mean trait values and ITV and detected patterns of community assembly processes with null models. We found that most ITV explained about 40% variance accounting the total trait variation, indicating that ITV is comparable to the among-species trait variability. The observed among-species RaoQ index was significantly lower than expected, and the observed within- and among-species CWM values significantly differed from the expected, suggesting that both niche differentiation and habitat filtering drive community assembly. Our results clearly demonstrate that the within-species trait variation greatly contributes to trait variability and promotes plant coexistence by increasing niche differences within tree populations. Our findings put up a new sight focusing on the individual functional trait values to improve strategies of species selection in forest management practices.KeywordsCommunity assemblyInterspecific variationIntraspecific variationNiche differentiationHabitat filteringTropical cloud forest