Rainfall pulse response of carbon fluxes in a temperate grass ecosystem in the semiarid Loess Plateau

Rainfall pulses can significantly influence carbon cycling in water limited ecosystems. The magnitude of carbon flux component responses to precipitation may vary depending on precipitation amount and antecedent soil moisture, associated with nonlinear responses of plants and soil microbes. The present study was carried out in a temperate grass ecosystem during 2013–2015 in the semiarid Loess Plateau of China, to examine the response of carbon fluxes to precipitation using the “threshold-delay” model. The unique contribution of environmental variables, such as precipitation amount and antecedent soil moisture before rainfall (SWC_antecedent) to carbon fluxes in response to rainfall were also investigated. The lower threshold of effective rainfall was 6.6 mm for gross ecosystem production (GEP), 8.5 mm for net ecosystem production (NEP) and 4.5 mm for ecosystem respiration (RE); and the upper threshold of effective rainfall was 21.4 mm for GEP and NEP, and 16.8 mm for RE. Rainfall amount...降雨脉冲可显著影响水分受限生态系统的碳循环。碳通量组分对降水的响应强度会随降水量与前期土壤含水量的变化而改变，这与植物和土壤微生物的非线性响应密切相关。本研究于2013至2015年在中国半干旱黄土高原的温带草原生态系统中开展，采用“阈值-延迟”模型探究碳通量对降水的响应特征，并同时考察了降水量、降雨前前期土壤含水量（SWC_antecedent）等环境变量对降雨响应过程中碳通量的独有贡献。研究结果显示：生态系统总初级生产力（GEP，gross ecosystem production）的有效降雨下限阈值为6.6 mm，净生态系统生产力（NEP，net ecosystem production）为8.5 mm，生态系统呼吸（RE，ecosystem respiration）为4.5 mm；而有效降雨上限阈值则为：GEP与NEP均为21.4 mm，RE为16.8 mm。降水量……