Functional features of tropical montane rain forests along a logging intensity gradient

Abstract

Logging is a pervasive disturbance, which often causes extensive destruction of forest community structure and severely impacts biodiversity in tropical regions. Previous work on the effects of anthropogenic activities on biodiversity have concentrated on taxonomic diversity. However, the effects of disturbances such as logging on the functional composition of communities (and thereby, ecosystem function) are poorly understood. Here, we examined variation in the functional traits and assembly processes of tropical montane rain forest communities along a gradient of logging intensity (clear-cut, selective logging, and old-growth) at three spatial scales (100 m2, 400 m2, and 2500 m2) in China. We measured six functional traits of species, including specific leaf area (SLA), leaf dry matter content (LDMC), leaf chlorophyll (LChl), leaf nitrogen content (LNC), leaf phosphorus content (LPC), and wood density (WD) in each forest plot. Functional composition changed along the disturbance gradient from logged to old-growth forests. Species with resource-acquisitive strategies (high SLA, LNC, and LPC) dominated the clear-cut forest. In contrast, species with resource-conservative strategies (high LDMC, LChl, and WD) dominated the old-growth forest, while species in the selectively-logged forest showed intermediate values. Across forests with different logging intensities, environmental filtering appeared to be the key process governing community assembly. Spatial scale had a significant effect on functional diversity and community assemblage but did not affect functional traits at the community level. At larger spatial scales, the functional richness and functional dispersion of the three forest types all increased and different community assembly processes were more obvious. Logged forests still need more time to recover levels of functional diversity observed in old-growth forest. Selective logging maintained more functional diversity than clear-cutting in these tropical montane rain forests.