[Dynamic changes of topsoil organic carbon in subalpine spruce plantation at different succession stages in western Sichuan Province].

Soil samples at 0-30 cm depth were collected from the primary spruce (Picea asperata) forest and its plantations at different succession stages (22-, 47-, and 65-year-old) in subalpine zone of western Sichuan Province to study the dynamic changes of soil organic carbon stock and labile organic carbon content. The soil total organic carbon (TOC) stocks in 0-10, 10-20, and 20-30 cm soil layers decreased from 95.87, 79.08, and 71.55 t x hm(-2) in 22-year-old plantation to 56.12, 34.75, and 31.06 t x hm(-2) in 65-year-old plantation, respectively, and the TOC stocks in these soil layers in 47 and 65-year-old plantations were less than those (88.08, 71.16 and 64.81 t x hm(-2), respectively) in primary forest. The easily oxidizable organic carbon (EOC) contents in 0-10, 10-20, and 20-30 cm soil layers decreased from 35.89, 26.91, and 26.00 g x kg(-1) in primary forest to 20.25, 14.50, and 12.36 g x kg L(-1) in 65-year-old plantation, the microbial biomass carbon (MBC) contents decreased from 524.44, 273.26, and 257.97 mg x kg(-1) in primary forest to 312.41, 186.95, and 152.18 mg x kg(-1) in 65-year-old plantation, and the particulate organic carbon (POC) contents decreased from 40.23, 27.10, and 19.55 g x kg(-1) in primary forest to 12.33, 7.31, and 5.32 g x kg(-1) in 65-year-old plantation, respectively. The results suggested that within the long succession period of primary P. asperata forest to its plantations in the subalpine zone of western Sichuan Province, soil TOC and labile organic carbon were in the state of net consumption.