Content and seasonal change in soil labile organic carbon under different forest covers
不同森林植被下土壤活性有机碳含量及其季节变化

Based on the concentrations of soil labile organic carbon (SLOC) pools under native evergreen broad-leaved forest (NBF), and three plantations of pure Cunninghamia lanceolata , pure Michelia macclurei and their mixed forest in different seasons, the effect of forest types on the content and seasonal changes of SLOC was analyzed for Huitong County of Hunan Province. The results show that SLOC content decreases after native evergreen broad-leaved forest are substituted by planted forest. Compared with C. lanceolata plantation, C. lanceolata and M. macclurei mixed forest (MCM) increases SLOC content. However, the difference is statistically insignificant except for water-soluble organic carbon (WSOC). Substantial seasonal fluctuations in SLOC under forests are observed. Throughout the year, WSOC decreases in the following order of NBF > MCM > pure M. macclurei plantation (PM) > pure C. lanceolata plantation (PCF). For soil microbial biomass carbon (MBC), hot-water extractable C (HWC) and hot-water extractable carbohydrate-C (HWcC) is in the following order of NBF > PM > MCM > PCF. Compared with PCF, MCM increases soil quality. However, seasonal trends of SLOC under different forest covers are not completely consistent, suggesting that seasonal fluctuations in SLOC are influenced not only by climatic factors like temperature and precipitation, but also by vegetation type.