Li Xiaojie, Feng Jiguang, Zhang Qiufang, Zhu Biao
Institute of Ecology, College of Urban and Environmental Sciences, Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University, Beijing 100871, China.
School of Geographical Sciences, Fujian Normal University, Fuzhou 350007, China.
Sci Total Environ. 2023 Dec 15;904:166170. doi: 10.1016/j.scitotenv.2023.166170. Epub 2023 Aug 9.
Fresh organic carbon (C) input will accelerate or inhibit the mineralization of native soil organic carbon (SOC), which is called positive or negative priming effect (PE), respectively. However, little is known about how warming affects the PE. Here, we adopted a widely-used ratio of SOC mineralization between substrate-added and unadded-control treatments to represent PE intensity and used the PE difference between ambient-control temperature and elevated temperature to indicate the effect of warming on PE (ΔPE). By conducting a meta-analysis of 146 observations from 57 independent soils worldwide, we found that experimental warming significantly decreased the PE by 0.26 (unitless). Among ecosystems, warming significantly suppressed the PE of cropland and grassland soils by 0.43 and 0.21 respectively, but did not change the PE of forest soils. Moreover, we found significant positive correlations of ΔPE with the initial soil C/N ratio and the effect size of warming on microbial biomass. Between substrate types (i.e., containing N or not), warming significantly decreased the PE induced by N-containing substrates. These results suggested that the response of PE to warming is likely regulated by soil N availability and warming-induced changes in microbial biomass. As such, we proposed a conceptual framework-the microbial N mining hypothesis dominates in soils with low C/N ratio where warming inhibits PE by promoting N mineralization, while the stoichiometric decomposition hypothesis dominates in soils with high C/N ratio where warming stimulates PE by promoting N mineralization. Collectively, these findings provide important insights into how warming affects SOC dynamics via inhibiting PE, which may weaken the positive feedback between soil C emission and climate warming.
新鲜有机碳（C）的输入会加速或抑制土壤原生有机碳（SOC）的矿化作用，分别被称为正激发效应（PE）或负激发效应。然而，关于升温如何影响激发效应，我们知之甚少。在这里，我们采用添加底物处理与未添加底物的对照处理之间SOC矿化率的常用比值来表示激发效应强度，并利用环境对照温度与升温之间的激发效应差异来指示升温对激发效应的影响（ΔPE）。通过对全球57种独立土壤的146个观测数据进行荟萃分析，我们发现实验升温显著降低了激发效应，降低幅度为0.26（无量纲）。在不同生态系统中，升温显著抑制了农田和草地土壤的激发效应，分别降低了0.43和0.21，但对森林土壤的激发效应没有影响。此外，我们发现ΔPE与初始土壤碳氮比以及升温对微生物生物量的效应大小之间存在显著正相关。在底物类型（即是否含氮）之间，升温显著降低了含氮底物诱导的激发效应。这些结果表明，激发效应对升温的响应可能受土壤氮有效性和升温诱导的微生物生物量变化的调控。因此，我们提出了一个概念框架——微生物氮挖掘假说在低碳氮比土壤中占主导地位，升温通过促进氮矿化抑制激发效应；而化学计量分解假说在高碳氮比土壤中占主导地位，升温通过促进氮矿化刺激激发效应。总的来说，这些发现为升温如何通过抑制激发效应影响土壤有机碳动态提供了重要见解，这可能会削弱土壤碳排放与气候变暖之间的正反馈。
