Environmental filtering of species with different functional traits into plant assemblages across a tropical coniferous-broadleaved forest ecotone

Abstract

Ecotones between coniferous and broadleaved forests in tropical regions are poorly understood. Our aim was to understand community assembly across the ecotones by integrating changes in both plant functional traits and environmental factors. The coniferous, ecotone, and broadleaved zones along each of the 15 investigation transects were discerned and surveyed. We measured eight functional traits of 174 woody species and 10 environmental factors along transects across the ecotones. We assessed between-site differences by using ANOVA, and correlations between functional traits and the environmental factors by RDA ordination. With the variation of vegetation zones from coniferous through the ecotone to broadleaved, the functional traits of plants at the community level changed in accordance with the changes in soil and light regimes. The low soil nutrients and low soil water in the coniferous zone were the major constraints for most lowland rain forest species with acquisitive traits, while high soil nutrients, high soil water and low light in the broadleaved zone had strong filtering effects on the conifer and tropical monsoon rainforest species with conservative traits. The soil and light conditions were the major determinants for the functional community structure of the vegetation types across the tropical coniferous and broadleaved forest ecotone.