The research on the impact of rainfall on soil respiration is significant to predict accurately the carbon balance of terrestrial ecosystems under future climate change. It is consensus that a certain degree of drought would suppress soil respiration, as well as the processes of water, carbon and nitrogen would be excited after re-watering by precipitation or irrigation. However, some research showed the suppression of soil respiration by precipitation. As a disturbance factor, the effect of precipitation on soil respiration is complex because of different vegetation and soil type in different regions. It is necessary to reveal the impact of rainfall amount, intensity and duration on soil respiration under different soil water content, as well to make clear the turning point of suppression or excitation of soil respiration in different regions. In a maize cropland located at eastern Loess Plateau, soil respiration and its components was measured continuously around 3 rainfall incidents based on in situ observation technique, and the impact of rainfall on soil respiration and its components was analyzed. The study was conducted in Shouyang county, Shanxi Province. It is a semi-humid area. The seasonal variation of precipitation is large, about 70% of annual amount occurs from June to September. In the field of maize cropland, soil respiration and its components were measured continuously by LI-8150 Soil CO₂ Flux System. Soil respiration was divided into microbial respiration and root respiration respectively based on root exclude method. Each treatment was repeated twice, and there were 4 observation fields in total.
There were 3 rainfalls recorded during July and August, and we analyzed the variation of soil respiration and its components before and after the 3 rainfalls. The results showed that rainfall suppressed the soil CO₂ efflux obviously under high soil water content. When soil volumetric water content was higher than 21.2%, 20.7% and 21.8%, respectively, soil respiration, microbial respiration and root respiration decreased obviously with the increase of soil water content, and the sensitivity of soil respiration to soil temperature also decreased. The variation of soil respiration and its components were influenced by both soil temperature and moisture. The amount and duration of rainfall and soil water content before rainfall decided the intensity and duration of response to precipitation. The temperature sensitivity of soil respiration and its components were different with each other. The temperature sensitivity of microbial respiration was the highest, Q₁₀ was 5.14, and the second highest was soil respiration with Q₁₀ 3.86. The temperature sensitivity of root respiration was the lowest, and Q₁₀ was 3.24. The ratio of root respiration to soil respiration increased after rainfall because the different sensitivity of respiration to temperature and moisture. Two factor model, including soil temperature and soil water content, was able to evaluate the response of soil respiration and microbial respiration to the variation of environmental factors in the maize ecosystem.