Data from: Partitioning the effect of composition and diversity of tree communities on leaf litter decomposition and soil respiration

The decomposition of plant material is an important ecosystem process influencing both carbon cycling and soil nutrient availability. Quantifying how plant diversity affects decomposition is thus crucial for predicting the effect of the global decline in plant diversity on ecosystem functioning. Plant diversity could affect the decomposition process both directly through the diversity of the litter, and/or indirectly through the diversity of the host plant community and its affect on the decomposition environment. Using a biodiversity experiment with trees in which both functional and taxonomic diversity were explicitly manipulated independently, we tested the effects of the functional diversity and identity of the living trees separately and in combination with the functional diversity and identity of the decomposing litter on rates of litter decomposition and soil respiration. Plant traits, predominantly leaf chemical and physical traits, were correlated with both litter decomposition and soil respiration rates. Surface litter decomposition, quantified by mass loss in litterbags, was best explained by abundance-weighted mean trait values of tree species from which the litter was assembled (functional identity). In contrast, soil respiration, which includes decomposition of dissolved organic carbon and root respiration, was best explained by the variance in trait values of the host trees (functional diversity). This research provides insight into the effect of loss of tree diversity in forests on soil processes. Such understanding is essential to predicting changes in the global carbon budget brought on by biodiversity loss.植物残体分解是调控碳循环与土壤养分有效性的核心生态系统过程。因此，量化植物多样性对分解过程的影响，对于预测全球植物多样性下降对生态系统功能的作用至关重要。植物多样性可通过两条路径影响分解过程：一是直接通过枯落物（litter）自身的多样性，二是间接通过宿主植物群落的多样性及其对分解环境的调控效应。本研究依托一项林木生物多样性实验，该实验独立且可控地操控了功能多样性（functional diversity）与分类多样性（taxonomic diversity）。我们分别测试了活立木的功能多样性、功能特征身份（functional identity），以及分解用枯落物的功能多样性、功能特征身份，对枯落物分解速率与土壤呼吸速率的单独效应与联合效应。研究测定了植物性状（主要为叶片化学与物理性状），其与枯落物分解及土壤呼吸速率均存在相关性。通过分解袋（litterbags）质量损失量化的地表枯落物分解，其最优预测因子为构建该枯落物的林木物种的丰度加权平均性状值。与之相对，涵盖溶解性有机碳（dissolved organic carbon）分解与根系呼吸（root respiration）的土壤呼吸，其最优预测因子为宿主林木的性状值方差（即功能多样性）。本研究揭示了森林林木多样性丧失对土壤过程的影响机制，此类认知对于预测生物多样性丧失引发的全球碳收支（carbon budget）变化至关重要。