Trait-Based Community Assembly along an Elevational Gradient in Subalpine Forests: Quantifying the Roles of Environmental Factors in Inter- and Intraspecific Variability.

Ya-Huang Luo,Shao-Lin Tan,Marc William Cadotte,Jie Liu,Yue-Hua Wang,Lian-Ming Gao,De-Zhu Li,Kun Xu,Kurt O Reinhart

doi:10.1371/journal.pone.0155749

Abstract

Understanding how communities respond to environmental variation is a central goal in ecology. Plant communities respond to environmental gradients via intraspecific and/or interspecific variation in plant functional traits. However, the relative contribution of these two responses to environmental factors remains poorly tested. We measured six functional traits (height, leaf thickness, specific leaf area (SLA), leaf carbon concentration (LCC), leaf nitrogen concentration (LNC) and leaf phosphorus concentration (LPC)) for 55 tree species occurring at five elevations across a 1200 m elevational gradient of subalpine forests in Yulong Mountain, Southwest China. We examined the relative contribution of interspecific and intraspecific traits variability based on community weighted mean trait values and functional diversity, and tested how different components of trait variation respond to different environmental axes (climate and soil variables). Species turnover explained the largest amount of variation in leaf morphological traits (leaf thickness and SLA) across the elevational gradient. However, intraspecific variability explained a large amount of variation (49.3%–76.3%) in three other traits (height, LNC and LPC) despite high levels of species turnover. The detection of limiting similarity in community assembly was improved when accounting for both intraspecific and interspecific variability. Different components of trait variation respond to different environmental axes, especially soil water content and climatic variables. Our results indicate that intraspecific variation is critical for understanding community assembly and evaluating community response to environmental change.

Highlights

Plant functional traits are linked to the ecological strategies of species and directly influence species interactions, making them fundamental drivers of community assembly [1,2,3]
For specific leaf area (SLA), the community weighted mean (CWM) trait variation was almost completely generated by interspecific variation, which accounted for 89.0% of the total variation of SLA, and there was positive covariation between interspecific and intraspecific variation among the plots (Table 1)
The only exception we found was when we accounted for intraspecific variability in the CWM of leaf thickness, which significantly deviated from null expectations across all plots (P = 0.03), and the range of leaf carbon concentration (LCC), which was significantly smaller than expectations when both intra- and interspecific variability was included (P = 0.015) or when using interspecific variability alone (P = 0.025)

Summary

Introduction

Plant functional traits are linked to the ecological strategies of species and directly influence species interactions, making them fundamental drivers of community assembly [1,2,3]. Environmental filtering results in a relatively small range of trait values (i.e., under-dispersed or clustered) occurring in specific environmental conditions [9, 14], but other processes (such as competition) could select species with similar traits [15]. The composition of any given community likely results from a combination of environment filtering and limiting similarity [9, 19]. In addition to these deterministic processes, neutral dynamics randomly structure a community’s functional traits and community composition [20]

Methods

Results

Discussion

Conclusion