The carbon cycle of sandy lands in China and its global significance

The quantitative C dynamics of desertified lands in Northern China were pre dicted for the years 2000 and 2030, based on the areas and conversion rates (positive and negative) of desertified lands in the past forty years and o rganic carbon contents of soils. The top 1.0 m soil layer of natural desert ified lands in China contained some 7,841 Tg of organic carbon as of 1992. In China, over the last 40 years, a total of 2,812 Tg of organic carbon was released from desert lands and, in the reverse process about 644 Tg of org anic-C were fixed into lands undergoing desertification. Thus, China's dese rt lands have shown a net release of 2,168 Tg of organic-C over the past 40 years, equivalent to 7,949 Tg of CO2. By the year 2000, the area of desert ified lands in China had increased 40,300 km(2) and released 368 Tg of orga nic-C into the atmosphere. By 2030 this area will increase to 249,700 km(2) and release about 1,996 Tg of organic-C into the atmosphere. Net releases of 151 Tg and 1,243 Tg of organic-C can be expected by the year 2000 and 20 30, respectively. This would be equivalent to a net release of 553 Tg of CO 2 by 2000 and 4,558 Tg by 2030. Thus, the organic carbon released through l and desertification in China could be an important factor affecting changes in concentrations of greenhouse gases worldwide.