陆地生态系统凋落物分解对全球气候变暖的响应

 陆地生态系统凋落物分解是全球碳收支的一个重要组成部分, 主要受气候、凋落物质量和土壤生物群落的综合控制。科学家们普遍认为全球气候变化将对陆地生态系统凋落物分解产生复杂而深远的影响。该文结合凋落物分解试验的常用方法——缩微试验、原位模拟实验和自然环境梯度实验, 归纳现有研究结果, 意在揭示全球气候变化对陆地生态系统凋落物分解的直接影响(温度对凋落物分解速率的影响)和间接影响(温度对凋落物质量、土壤微生物群落及植被型的影响)的普遍规律。各种研究方法都表明: 在水分条件理想的情况下, 温度升高往往能加快凋落物的分解速率; 原位模拟实验中, 凋落物分解速率因物种、增温方法和地理方位而异; 全球气候变化能改变凋落物质量, 但可能不会在短期内影响凋落物的分解速率; 凋落物质量和可分解性的种间差异远大于增温所引发的表型响应差异, 那么, 气候变化所引发的植物群落结构和物种组成的变化将对陆地生态系统凋落物分解产生更强烈的影响; 土壤生物群落如何响应全球气候变化, 进而怎样影响凋落物分解过程, 这些都还存在着极大的不确定性。

A REVIEW OF RESPONSES OF LITTER DECOMPOSITION IN TERRESTRIAL ECOSYSTEMS TO GLOBAL WARMING

Litter decomposition in terrestrial ecosystems, an important process in the global carbon budget, is mainly controlled by climate, litter quality and soil organisms. Scientists generally think that global warming could have profound and complicated effects on litter decomposition in terrestrial ecosystems. In this review, we summarized results from microcosm studies, in situ artificial warming experiments and natural gradient research to evaluate direct effects (temperature increment on litter decomposition rates) and indirect effects (temperature increment on litter quality, soil organisms and vegetation) of global wanning on litter decomposition in terrestrial ecosystems. Each method of study indicated that temperature elevation can often increase litter decomposition rates when litter moisture is maintained. Experimental warming studies implied that litter decomposition rates vary among species, methods and geographical sites. Global warming is likely to alter litter quality and decomposability, but these changes will not influence short-term litter decomposition rates. Interspecific differences in litter quality and decomposability are dramatically stronger than warming-induced differences. Thus, warming-induced changes in species composition and community structure may have stronger impacts on litter decomposition processes in terrestrial ecosystems. Effects of warming-induced changes in soil organisms on litter decomposition are highly uncertain.