Soil carbon sequestration in China through agricultural intensification, and restoration of degraded and desertified ecosystems

The industrial emission of carbon (C) in China in 2000 was about I Pg yr(-1), which may surpass that of the United States (1.84 Pg C) by 2020. China's large land area, similar in size to that of the United States, comprises 124 Mha of cropland, 400 Mha of grazing land and 134 Mha of forestland. Terrestrial C pool of China comprises about 35-60 Pg in the forest and 120-186 Pg in soils. Soil degradation is a major issue affecting 145 Mha by different degradative processes, of which 126 Mha are prone to accelerated soil erosion. Total annual loss by erosion is estimated at 5.5 Pg of soil and 15.9 Tg of soil organic carbon (SOC). Erosion-induced emission of C into the atmosphere may be 32-64 Tg yr(-1). The SOC pool progressively declined from the 1930s to 1980s in soils of northern China and slightly increased in those of southern China because of change in land use. Management practices that lead to depletion of the SOC stock are cultivation of upland soils, negative nutrient balance in cropland. residue removal. and soil degradation by accelerated soil erosion and salinization and the like. Agricultural practices that enhance the SOC stock include conversion of upland to rice paddies, integrated nutrient management based on liberal use of biosolids and compost, crop rotations that return large quantities of biomass. and conservation-effective systems. Adoption of recommended management practices can increase SOC concentration in puddled soil. red soil, loess soils, and salt-affected soils. In addition, I soil restoration has a potential to sequester SOC. Total potential of soil C sequestration in China is 105-198 Tg C yr(-1) of SOC and 7-138 Tg C yr(-1) for soil inorganic carbon (SIC). The accumulative potential of soil C sequestration of I I Pg at an average rate of 224 Tg yr(-1) may be realized by 2050. Soil C sequestration potential can offset about 20 per cent of the annual industrial emissions in China. Copyright (C) 2002 John Wiley Sons, Ltd.