Influence of Precipitation Change on Soil Respiration in Desert Grassland

Abstract

Global climate change has significantly changed precipitation patterns. Soil respiration (SR), as an important pathway through which CO2 is released from the soil carbon pool into the atmosphere, may affect the carbon cycle process of terrestrial ecosystems and have a feedback effect on global climate change in response to precipitation change. However, at present there is limited understanding of how SR is affected by precipitation change. Field precipitation control experiments were conducted (with -40%, -20%, natural, 20%, and 40% precipitation) on desert grassland in the west of the Loess Plateau, to investigate the influence of precipitation change on SR dynamics and its relationship with soil water content, soil temperature, aboveground biomass, soil organic carbon, microbial biomass carbon, carbon-nitrogen ratio, and other factors. The results show that the diurnal variations of SR under different precipitation treatments were consistent in unimodal and bimodal models over three years. SR showed an increasing trend with added precipitation, relative to the control, and significant differences were observed between the second year (wetter) and the third year (drier) of the precipitation-manipulation experiment, indicating that precipitation changes had a legacy effect on SR. At the same time, SR was lowest under the -40% treatment and highest under the 40% treatment during the wetter year. The negative response of SR to precipitation exclusion treatments was stronger than the positive response to precipitation addition treatments. SR in drier years was significantly higher under precipitation addition treatments than the control, and the positive response of SR to increased precipitation treatment was significantly stronger than that under decreased precipitation treatment. In addition, soil water content, aboveground biomass, soil organic carbon, and carbon-nitrogen ratio were the environmental factors that obviously affected SR and increased with additional precipitation. SR increased with increases in soil water content, aboveground biomass, soil organic carbon, and carbon-nitrogen ratio, but decreased with increases in microbial biomass carbon. Among these factors, soil water content had the highest interpretation rate for SR, indicating that soil water content was the main environmental factor controlling SR in desert grassland. In both wetter and drier years, the amplitude of plant biomass input was lower than the amplitude of SR output under precipitation change, indicating that precipitation change may be unfavorable to soil carbon sequestration, especially in drier years, when precipitation change has a stronger influence on carbon pool output. Therefore, precipitation changes on SR in desert grassland in various dry and wet years may have different influences on the carbon cycle process of ecosystems, thus providing a reference for regional carbon budget assessment.