Effects of Grassland Conversion From Cropland on Soil Respiration on the Semi-Arid Loess Plateau, China

Soil respiration is considered to be the second largest terrestrial carbon flux, and is influenced by land use changes. The impact of a cropland to grassland program on soil respiration was quantified. It tried to identify the dominant factors driving soil respiration along the restoration project of "Grain for Green Program" on the semiarid Loess Plateau, China. Soil respiration and different abiotic and biotic factors were measured for cropland and grasslands after five, 15, and 30 years of natural restoration. Soil respiration (g Cm(-2)d(-1)) was significantly greater for grassland with litter left that had been restored for 15 years than for cropland and grassland (five years), but did not significantly change from 15 to 30 years. Soil temperature and litter were the main factors affecting soil respiration along the restoration chronosequence. The contribution of litter to soil respiration after 15 years restoration was about 12%. The temperature sensitivity of the soil respiration ranged from 1.30 in the wheat land to 2.44 in the 30 years restoration grassland with litter left, and it increased with litter removed in the grasslands. Our findings suggest that grasslands after 15-year natural restoration must be utilized properly to balance changes in soil respiration with the soil organic carbon accumulation during the cropland to grassland restoration process.