Effect of climatic changes and human activity on soil carbon in desertified regions of China

A total of 340 soil samples from 17 different types of sandy land regions in China were analyzed for soil organic carbon (SOC). Stepwise regression served to identify correlations betweenSOCand a number of climatic factors measured at the sampling sites: winter, summer, nighttime and daytime air temperatures (AT) and precipitation. In desertified lands SOC showed a direct correlation with precipitation, but no significant relationship with the mean air temperature. However, in northwest and northeast China decreases in SOC were linked to rises in day/night and seasonal temperatures, while in north China they were linked to a rise in mean temperature. Over the entire study period (1950–1990), precipitation in the region decreased by 25 mm decade−1, while the mean air temperature increased by 0.14◦, 0.28◦ and 0.15◦ decade−1 in the northwest, northeast and north central regions, respectively. Driven by rises in day/night and seasonal temperatures, long-term alterations to global ecosystem processes, particularly the carbon cycle, may significantly alter the number and diversity of plants in desertified ecosystems. Based on multiple regression analysis, over the past 40 years, about 20% of emissions from SOC in the northeast were attributable to air temperature; in the north central region 31 and 16% of emissions were attributable to precipitation and mean AT, respectively; while in the northwest 28, 18 and 32% of the emissions were attributable to mean AT, nighttime temperature, and decreasing precipitation, respectively. It is obvious that human activities are the main single causative factor in the release of SOC-derived greenhouse gases to the atmosphere from desertified areas.