Pulse Effect of Precipitation: Spatial Patterns and Mechanisms of Soil Carbon Emissions
Zhaoxia Jiang, Hongfeng Bian, Li Xu, Mingxu Li, Nianpeng He
Abstract
The rapid and strong release of CO 2 caused by precipitation (known as the pulse effect) is a common phenomenon that significantly affects ecosystem C cycling. However, the degree to which the pulse effect occurs overlarge regional scales remains unclear. In this study, we conducted continuous and high-frequency measurements of soil CO 2 release rates ( R s ) for 48 h after simulated precipitation, along a precipitation gradient of different grassland types (i.e., meadow, typical, and desert) in Inner Mongolia, China. Pulse effects were assessed using the maximum R s ( R soil–max ) and accumulated CO 2 emissions ( A Rs–soil ). Strong precipitation pulse effects were found in all sites; however, the effects differed among grassland types. In addition, an apparent decrease in both R soil–max and A Rs–soil was observed from the east to west, i.e., along the decreasing precipitation gradient. A Rs–soil values followed the order: temperate meadow grassland (0.097 mg C g –1 soil) > typical temperate grassland (0.081 mg C g –1 soil) > temperate desert grassland (0.040 mg C g –1 soil). Furthermore, R soil–max and A Rs–soil were significantly positively correlated with soil quality (SOC, POC, and N, etc.; P < 0.01). A Rs–soil ( P < 0.05) and A Rs–SOC ( P < 0.01) were significantly affected. A Rs–soil and A Rs–SOC were also positively correlated with soil microbial biomass significantly ( P < 0.05). R soil–max and A Rs–soil had similar spatial variations and controlling mechanisms. These results greatly support the substrate supply hypothesis for the effects of precipitation pulses, and provide valuable information for predicting CO 2 emissions. Our findings also verified the significant effect of soil CO 2 release from precipitation pulses on the grasslands of arid and semi-arid regions. Our data provide a scientific basis for model simulations to better predict the responses of ecosystem carbon cycles in arid and semi-arid regions under predicted climate change scenarios.