Understanding the dominant controls on litter decomposition

Litter decomposition is a biogeochemical process fundamental to element cycling within ecosystems, influencing plant productivity, species composition and carbon storage. Climate has long been considered the primary broad-scale control on litter decomposition rates, yet recent work suggests that plant litter traits may predominate. Both decomposition paradigms, however, rely on inferences from cross-biome litter decomposition studies that analyse site-level means. We re-analyse data from a classical cross-biome study to demonstrate that previous research may falsely inflate the regulatory role of climate on decomposition and mask the influence of unmeasured local-scale factors. Using the re-analysis as a platform, we advocate experimental designs of litter decomposition studies that involve high within-site replication, measurements of regulatory factors and processes at the same local spatial grain, analysis of individual observations and biome-scale gradients. Synthesis. We question the assumption that climate is the predominant regulator of decomposition rates at broad spatial scales. We propose a framework for a new generation of studies focused on factoring local-scale variation into the measurement and analysis of soil processes across broad scales. Such efforts may suggest a revised decomposition paradigm and ultimately improve confidence in the structure, parameter estimates and hence projections of biogeochemical models.

枯落物分解（litter decomposition）是生态系统内元素循环的核心生物地球化学过程，对植物生产力、物种组成与碳储量均具有关键调控作用。长期以来，气候被视为调控枯落物分解速率的核心大尺度驱动因子，但近期研究表明植物枯落物性状或可占据主导地位。然而，现有两种分解范式均依赖于跨生物群区（biome）枯落物分解研究的推论，此类研究普遍采用样地水平均值开展分析。本研究通过重新分析一项经典跨生物群区研究的数据集，证实此前研究或存在高估气候对分解过程调控作用的问题，同时掩盖了未被观测的局地尺度因子的影响。以本次重新分析为研究基础，我们倡议枯落物分解研究采用如下实验设计：提升样地内重复采样密度，在相同局地空间粒度下开展调控因子与过程的同步观测，对单个观测样本进行分析，并覆盖生物群区尺度的环境梯度。综合分析显示，我们对"气候是大空间尺度下分解速率的主要调控因子"这一传统假设提出了质疑。我们提出了新一代研究的框架，其核心是将局地尺度变异纳入跨大尺度土壤过程的观测与分析体系。此类研究有望推动分解范式的修订，并最终提升生物地球化学模型的结构合理性、参数估算精度乃至预测结果的可信度。