The within-species leaf economic spectrum does not predict leaf litter decomposability at either the within-species or whole community levels.

摘要

Despite recent progress in characterizing the within-species variability (WSV) of plant functional traits, the importance of this WSV in driving ecological processes such as leaf litter decomposability within species or at the whole community level is poorly understood. We ask whether leaf and litter functional traits vary within species to form a spectrum of variability analogous to the leaf economics spectrum that occurs among species. We also ask whether this spectrum of trait variation within species is an important driver of leaf litter decomposability. To address these questions, we quantified both WSV and between-species variation of leaf and litter traits and litter decomposability of 16 co-occurring temperate rain forest plant species along soil toposequences characterized by strong shifts in soil nutrient status in New Zealand. We found considerable WSV of both leaf and litter traits for all species, and a within-species spectrum of coordinated trait variation for 11 species. The WSV of leaf and to a lesser extent foliar litter C to N and C to P values were often strongly related to soil C to N and C to P ratios across plots. Further, in many cases, WSV and its covariation with species turnover contributed significantly to the community-level aggregate trait response to variation in soil fertility. Contrary to our expectations, the WSV in leaf and litter traits did not generally predict within-species variation in leaf litter mass loss, nor N and P release, during decomposition. Further, inclusion of WSV did not improve predictions of leaf litter decomposability using community-level trait measures. Synthesis. Our findings support the view that WSV of plant functional traits is an important component of plant community responses to environmental factors such as soil fertility. However, the apparent decoupling of WSV of leaf economic traits from WSV of ecological processes such as litter decomposability suggests that consideration of WSV may not be necessary to understand the contributions of trait variation to determining the breakdown of plant litter and therefore, potentially, ecosystem processes. Our findings support the view that within species variation (WSV) of plant functional traits is an important component of plant community responses to environmental factors such as soil fertility. However, the apparent decoupling of WSV of leaf economic traits from WSV of litter decomposability suggests that consideration of WSV may not be necessary to understand the contributions of trait variation to determining the breakdown of plant litter and therefore, potentially, ecosystem processes.