Microclimatic variation in tropical canopies: A glimpse into the processes of community assembly in epiphytic bryophyte communities

TL;DR

This study investigates how microclimatic variation, light, and host tree size influence the composition and phylogenetic structure of epiphytic bryophyte communities in tropical rainforests, revealing significant vertical turnover within trees.

Contribution

It provides new insights into the relative importance of microclimatic factors and host tree characteristics in shaping epiphyte community assembly at fine spatial scales.

Findings

Vertical bryophyte community turnover is about 30% higher than horizontal turnover.

Microclimatic variation from tree base to canopy significantly influences community composition.

Vertical microclimatic differences are more impactful than host tree age in community assembly.

Abstract

Epiphytic communities offer an original framework to disentangle the contributions of environmental filters, biotic interactions and dispersal limitations to community structure at fine spatial scales. We determine here whether variations in light, microclimatic conditions and host tree size affect the variation in species composition and phylogenetic structure of epiphytic bryophyte communities, and hence, assess the contribution of environmental filtering, phylogenetic constraints and competition to community assembly.A canopy crane giving access to 1.1 ha of tropical rainforest in Yunnan (China) was employed to record hourly light and microclimatic conditions from 54 dataloggers and epiphytic bryophyte communities from 408 plots. Generalized Dissimilarity Modelling was implemented to analyse the relationship between taxonomic and phylogenetic turnover among epiphytic communities, host-tree characteristics and microclimatic variation.Within-tree vertical turnover of bryophyte communities was significantly about 30% higher than horizontal turnover among-trees. Thus, the sharp vertical variations in microclimatic conditions from tree base to canopy are more important than differences in age, reflecting the likelihood of colonization, area, and habitat conditions between young and old trees, in shaping the composition of epiphytic bryophyte communities.