Sino-French Institute for Earth System Science, College of Urban and Environmental Sciences, Peking University, Beijing, China.
Laboratorio de Biodiversidad y Funcionamiento Ecosistémico, Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS), CSIC, Sevilla, Spain.
Glob Chang Biol. 2023 Aug;29(15):4412-4429. doi: 10.1111/gcb.16765. Epub 2023 Jun 5.
Microbial communities in soils are generally considered to be limited by carbon (C), which could be a crucial control for basic soil functions and responses of microbial heterotrophic metabolism to climate change. However, global soil microbial C limitation (MCL) has rarely been estimated and is poorly understood. Here, we predicted MCL, defined as limited availability of substrate C relative to nitrogen and/or phosphorus to meet microbial metabolic requirements, based on the thresholds of extracellular enzyme activity across 847 sites (2476 observations) representing global natural ecosystems. Results showed that only about 22% of global sites in terrestrial surface soils show relative C limitation in microbial community. This finding challenges the conventional hypothesis of ubiquitous C limitation for soil microbial metabolism. The limited geographic extent of C limitation in our study was mainly attributed to plant litter, rather than soil organic matter that has been processed by microbes, serving as the dominant C source for microbial acquisition. We also identified a significant latitudinal pattern of predicted MCL with larger C limitation at mid- to high latitudes, whereas this limitation was generally absent in the tropics. Moreover, MCL significantly constrained the rates of soil heterotrophic respiration, suggesting a potentially larger relative increase in respiration at mid- to high latitudes than low latitudes, if climate change increases primary productivity that alleviates MCL at higher latitudes. Our study provides the first global estimates of MCL, advancing our understanding of terrestrial C cycling and microbial metabolic feedback under global climate change.
土壤中的微生物群落通常被认为受到碳 (C) 的限制，这可能是控制基本土壤功能和微生物异养代谢对气候变化响应的关键因素。然而，全球土壤微生物碳限制（MCL）很少被估计，也了解甚少。在这里，我们根据代表全球自然生态系统的 847 个地点（2476 个观测值）的胞外酶活性阈值，预测了 MCL，将其定义为相对于氮和/或磷，底物 C 的有限可利用性以满足微生物代谢需求。结果表明，全球陆地表面土壤中只有约 22%的地点显示微生物群落存在相对 C 限制。这一发现挑战了土壤微生物代谢普遍存在 C 限制的传统假设。在我们的研究中，C 限制的地理范围有限，主要归因于植物凋落物，而不是已被微生物加工的土壤有机质，作为微生物获取的主要 C 源。我们还确定了预测的 MCL 具有显著的纬度格局，中高纬度的 C 限制更大，而热带地区通常不存在这种限制。此外，MCL 显著限制了土壤异养呼吸速率，这表明如果气候变化增加了缓解高纬度地区 MCL 的初级生产力，那么中高纬度地区的呼吸速率可能会相对增加更多。我们的研究提供了全球 MCL 的首次估计，增进了我们对全球气候变化下陆地碳循环和微生物代谢反馈的理解。
