[Estimates and affecting factors of soil organic carbon storages in Yunnan-Guizhou-Guangxi Region of China].

Soil organic carbon (SOC) plays a key role in the terrestrial eco-systems. However, there is a large variation in SOC estimates at regional and global scales. In order to improve the accuracy of SOC estimates, the SOC storage in Yunnan-Guizhou-Guangxi Region of China (include Yunnan Province, Guizhou Province and Guangxi Zhuang Municipality) was estimated using 798 soil profiles and 1:500 000 digitized soil map, and the dominant affecting factors on SOC density were also discussed employing stepwise regression and path analysis. Results showed that the SOC storages estimated in the 0-20 cm and 0-100 cm layers are 4.39 Pg and 10.91 Pg, respectively; and the corresponding SOC density are 56.2 Mg x hm(-2) and 139.8 Mg x hm(-2), respectively. The mean SOC density of Yunnan-Guizhou-Guangxi Region is higher than that of China. The environmental factors (including altitude, longitude, latitude, annual mean precipitation and annual mean temperature), soil parent materials and land use could explain 37.9% and 30.7% of the variability of SOC density to the upper 20 cm and 100 cm, respectively. The environmental factors are the dominant affecting factors of SOC density. The effect of temperature is more important than that of precipitation, and the temperature and precipitation mainly vary with altitude and latitude, respectively. Except for temperature and precipitation, there are also other factors varying with altitude, longitude and latitude significantly affect SOC density. And the effects of other factors are more important than that of precipitation.