School of Forestry and Environmental Studies, Yale University, New Haven, CT, 06511, USA.
Department of Terrestrial Ecology, Netherlands Institute of Ecology (NIOO-KNAW), 6700 AB, Wageningen, The Netherlands.
Nat Ecol Evol. 2017 Dec;1(12):1836-1845. doi: 10.1038/s41559-017-0367-4. Epub 2017 Nov 13.
Our basic understanding of plant litter decomposition informs the assumptions underlying widely applied soil biogeochemical models, including those embedded in Earth system models. Confidence in projected carbon cycle-climate feedbacks therefore depends on accurate knowledge about the controls regulating the rate at which plant biomass is decomposed into products such as CO. Here we test underlying assumptions of the dominant conceptual model of litter decomposition. The model posits that a primary control on the rate of decomposition at regional to global scales is climate (temperature and moisture), with the controlling effects of decomposers negligible at such broad spatial scales. Using a regional-scale litter decomposition experiment at six sites spanning from northern Sweden to southern France-and capturing both within and among site variation in putative controls-we find that contrary to predictions from the hierarchical model, decomposer (microbial) biomass strongly regulates decomposition at regional scales. Furthermore, the size of the microbial biomass dictates the absolute change in decomposition rates with changing climate variables. Our findings suggest the need for revision of the hierarchical model, with decomposers acting as both local- and broad-scale controls on litter decomposition rates, necessitating their explicit consideration in global biogeochemical models.
我们对植物凋落物分解的基本理解为广泛应用的土壤生物地球化学模型提供了假设基础，包括那些嵌入地球系统模型中的假设。因此，对碳循环-气候反馈的预测的信心取决于对控制植物生物质分解为 CO 等产物的速率的准确了解。在这里，我们检验了凋落物分解的主要概念模型的基本假设。该模型假设，在区域到全球尺度上，分解速率的主要控制因素是气候（温度和湿度），在如此广泛的空间尺度上，分解者的控制作用可以忽略不计。利用从瑞典北部到法国南部的六个地点进行的区域尺度凋落物分解实验-并同时捕获潜在控制因素的内部和之间的变化-我们发现，与分层模型的预测相反，分解者（微生物）生物量强烈调节区域尺度上的分解。此外，微生物生物量的大小决定了随着气候变量的变化，分解速率的绝对变化。我们的研究结果表明，需要对分层模型进行修订，将分解者作为凋落物分解率的局部和广泛控制因素，这需要在全球生物地球化学模型中明确考虑。
