RESEARCH AND PROSPECTS FOR SOIL RESPIRATION OF FARMLAND ECOSYSTEMS IN CHINA

Farmland ecosystems are important terrestrial ecosystems, representing about 10.5% of the earth's surface, and their CO2 emission amounts about 21%-25% of anthropogenic greenhouse gases emission. Farmland ecosystems are affected intensively by human activities; therefore, soil respiration of farmland ecosystems and their impacts are very important in the carbon budget of terrestrial ecosystems, as well as the global carbon cycle and carbon budget. With a long history of extensive agriculture, China provides a laboratory for soil respiration research. We review the previous decade of research advances in soil respiration of farmland ecosystems in China. Heat-water factors, crop biological characteristics and agricultural management activities played key roles in regulating the spatial and temporal variations of soil respiration. Root respiration accounts for 13%-77% of soil respiration, but the amounts are uncertain. Rational fertilization, straw return to soil and no-tillage are useful to soil CO2 emission reduction and soil carbon sequestration. We discuss key issues and further tasks, including comparison of soil respiration among typical farmland ecosystems in different areas, spatial variations of soil respiration, simulation of factors controlling soil respiration, and mitigation options of soil CO2 emission.