中科院华南植物园生态中心鼎湖山站博士后杜悦在合作导师闫俊华研究员以及王应平研究员的共同指导下，以全球248篇降水量变化控制实验研究论文的观测数据为基础，分析了草地和森林两类生态系统土壤呼吸对降水量变化的响应。发现草地和森林两类生态系统土壤呼吸对降水量变化的响应表现为不同的非线性（图1）。在草地生态系统中，土壤呼吸的响应为负不对称性（negative asymmetry, 对降水量减少的敏感性更大）。而在森林生态系统中，土壤呼吸的响应则随着降水量变化的强度而呈现不同模式，在中强度降水量变化条件下表现为正不对称性（positive asymmetry, 对降水量増加的敏感性更大），而在极端降水量变化条件下为负不对称性。该结果将为预测土壤碳动态对降水量变化的响应和反馈提供可靠依据。同时，草地和森林两类生态系统土壤呼吸对极端降水量变化的响应表现为一致的负不对称性，这预示着在未来降水量变异增大（极端降水事件频发）的情形下，土壤碳排放将显著降低。
相关研究结果于近期发表在国际主流学术期刊Global Change Biology（《全球变化生物学》）（IF = 8.555，生态学7/168）上。该研究得到国家杰出青年科学基金、国家自然科学基金等项目的资助。论文链接：https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.15270.
图1. 土壤呼吸与降水量变化百分比的相关关系（Relationships of response ratios of soil respiration with percentage changes in precipitation in grasslands and forests.）
The response of soil respiration to precipitation change is asymmetric and differs between grasslands and forests
Intensification of the Earth’s hydrological cycle amplifies the interannual variability of precipitation, which will significantly impact on terrestrial carbon cycle. However, it is still unknown whether previously observed relationship between soil respiration and precipitation remains applicable under extreme precipitation change.
To address this question, the postdoctor DU Yue, under the joint guidance of Prof. YAN Junhua and WANG Yingping, conducted a global synthesis of observations from a large dataset of field experiments (248 published papers including 151 grassland studies and 97 forest studies) across a wide range of precipitation-manipulation.
The response of soil respiration to precipitation change was highly nonlinear or asymmetric, and differed significantly between grasslands and forests, between moderate and extreme precipitation changes. Soil respiration response was negatively asymmetric (concave-down) in grasslands, and double-asymmetric in forests with a positive asymmetry (concave-up) under moderate precipitation changes and a negative asymmetry (concave-down) under extreme precipitation changes (Figure 1). The different asymmetric responses of soil respiration between grasslands and forests will greatly improve our ability to forecast the carbon cycle consequences of increased precipitation variability. Specifically, the negative asymmetry of soil respiration response under extreme precipitation change suggests that the soil carbon efflux will decrease across grasslands and forests under future precipitation regime with more wet and dry extremes.
This study entitled “The response of soil respiration to precipitation change is asymmetric and differs between grasslands and forests” was published in Global Change Biology. For further reading, please refer to: https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.15270.