The Impact of Land Use/Cover Change on Soil Organic Carbon Stocks and Quality in Mid- subtropical Mountainous Ar ea of Southern China
中亚热带山区土地利用变化 对土壤有机碳储量和质量的影响

Land use/cover change (LUCC) is widely recognized as one of the most important driving forces of global carbon cycles. The influence of LUCC from native forest to plantations, secondary forest, orchard and arable land on soil organic carbon (SOC) stores and quality was investigated by using "space for time" method in mid-subtropical mountainous area of southern China. The results show that LUCC has led to great decreased SOC stocks and quality. Considerable SOC and light-fraction organic carbon (LFOC) have been stored in native forest (142.2 t hm-2 and 14.8 t·hm-2, respectively). When native forest was converted to plantations, secondary forest, orchard and arable land, the SOC stocks decreased by 25.6% -28%.7%, 38.0%, 31.8% and 51.2%, respectively. The LFOC stocks decreased by 52.2-57.2% when native forest was converted to woodland plantations and second forest, and by 82.1% -84.2% when to economic plantation, orchard and arable land. After the conversion, the ratios of LFOC to SOC (0-60 cm) decreased from 13.3% to about 3.0%-10.7%. The SOC and LFOC stored in the upper 20 cm soil were more sensitive to LUCC when compared to the subsurface soil layer. Comparison suggests that the effects of the above mentioned LUCC on carbon release and quality deline were greater than the global average level, which could be explained by the vulnerable natural environment and special human management practices. Thus, it is significant to protect vulnerable environment, restore vegetation coverage and afforest plantation reasonably in mountainous area in mid-subtropics, for enhancing soil carbon sequestration, mitigating elevated atmospheric CO2 and sustainably developing ecological services.