Coexistence of three common species in a temperate mixed forest: Linking seedling microhabitats and functional traits

Abstract

Community ecologists often assume that species-level trait differences drive habitat differentiation that promotes species coexistence. Direct empirical studies testing trait–habitat relationships in forest ecosystems are critical for understanding the functional basis of tree coexistence and predicting the effects of forest disturbance on diversity, but such studies have been rarely performed. Considering the importance of the regeneration niche in tree coexistence, here, we tested regeneration niche differentiation and species-level trait–habitat relationships by measuring nine microhabitat variables and seven functional traits of seedlings of three common tree species in a temperate mixed forest in Taibai Mountain in China. Our results showed that most tree seedlings grew in microhabitats with more light and distant neighbor than random points. The three species were separated in the microhabitat space defined by canopy cover and neighbor distance gradients and in the trait space defined by leaf economic traits, seed mass, and wood density. Leaf economic traits were mostly related to light microhabitat variables, whereas seed mass and stem wood density were mostly associated with neighbor distance. These results suggested that the heterogeneity of light availability and neighbor distance were the main ecological gradients in distinguishing different tree species in seedling microhabitats. Differences in seedling functional traits drive the differentiation of species regeneration niches, potentially facilitating the coexistence of tree species. Leaf economic traits, seed mass, and wood density could be used to predict the regeneration microhabitat of tree species.