Data from: Biotic and abiotic variables influencing plant litter breakdown in streams: a global study

Plant litter breakdown is a key ecological process in terrestrial and freshwater ecosystems. Streams and rivers, in particular, have high rates of carbon dioxide evasion and they contribute substantially to global carbon fluxes. However, there is little information available on the relative roles of different drivers of plant litter breakdown in fresh waters, particularly at large scales. We present a global-scale study of litter breakdown in streams to compare the roles of biotic, climatic and other environmental factors on breakdown rates. We conducted an experiment in 24 streams encompassing latitudes from 47.8ºN to 42.8ºS, using litter mixtures of local species differing in quality and phylogenetic diversity, and alder (Alnus glutinosa) to control for variation in litter traits. Our models revealed that breakdown of alder was driven by climate, with some influence of pH, while variation in breakdown of litter mixtures was explained mainly by litter quality and phylogenetic diversity. The influence of these litter variables and pH was modulated by temperature, indicating that different mechanisms may operate at different latitudes. These results reflect global variability caused by multiple factors, but unexplained variance points to the need for expanded global-scale comparisons.

植物碎屑分解（plant litter breakdown）是陆地与淡水生态系统中的核心生态过程。其中溪流与河流的二氧化碳逸出（carbon dioxide evasion）速率颇高，对全球碳通量（global carbon fluxes）贡献显著。然而，目前针对淡水生态系统中植物碎屑分解的各类驱动因子相对作用的相关研究仍较为匮乏，在大尺度研究层面尤为如此。本研究开展了一项全球尺度的溪流碎屑分解调查，旨在对比生物因子、气候因子及其他环境因子对分解速率的影响作用。本研究在覆盖北纬47.8°至南纬42.8°纬度区间的24条溪流中开展野外实验：以品质与系统发育多样性（phylogenetic diversity）存在差异的本土物种碎屑混合物作为实验材料，并以桤木（Alnus glutinosa）作为对照以消除碎屑性状（litter traits）差异带来的干扰。模型结果显示，桤木碎屑的分解主要受气候因子调控，pH值也存在一定影响；而本土物种碎屑混合物的分解速率差异则主要由碎屑品质与系统发育多样性决定。上述碎屑相关变量与pH值的影响效应均受温度调控，这表明不同纬度下可能存在不同的调控机制。本研究结果反映了多因子驱动下的全球尺度变异特征，但仍存在未解释方差（unexplained variance），这提示未来需要开展更多全球尺度的对比研究以完善相关认知。