Soil Respiration and Driving Factors of Farmland Ecosystems in China

Soil respiration plays a crucial role in global carbon (C) budget. It is important to conduct the research in the typical agricultural regions, China to understand its spatial and temporal variations and their controlling factors. This will benefit not only quantitative evaluation of soil respiration at a regional scale, but also the agricultural C budget in China and even in the world. In this study, we integrated soil respiration data in agricultural ecosystems between 2000 and 2012 in China, and analyzed the seasonal and spatial variations and the factors influencing soil respiration in five typical agricultural regions (Southeast, Southwest, North, Northwest, and Northeast China). The results showed that obvious seasonal variation was observed in five agricultural regions. The annual mean rate of soil respiration in farmland ecosystems of China was (682.8±18.3) g C m-2 year-1, and total C efflux from soil respiration in agricultural region of China was about 0.90 Pg C year-1. The order of soil respiration rate in five agricultural regions was Southeast>Southwest>North>Northeast>Northwest. The significant difference in soil respiration rates was found between water-cultivation and dry-cultivation regions (P<0.05). Soil respiration in dry-cultivation regions was 1.3 times higher than that in water-cultivation ones. Soil respiration rate was significantly affected by crop types (P<0.05), with an order of cotton>corn>soybean>rice>wheat. Significant correlations were found in soil respiration with annual mean temperature, soil temperature, soil water content, and NPP (P<0.01). There was no significant correlation between soil respiration and annual precipitation.