不同森林植被下土壤活性有机碳含量及其季节变化

通过对湖南省会同县地区不同季节地带性常绿阔叶林、杉木纯林、火力楠纯林以及杉木火力楠混交林土壤各活性有机碳的含量测定,分析了森林植被对土壤活性碳库及其季节变化的影响.结果表明,常绿阔叶林转变为人工林后,土壤活性有机碳含量明显降低;与杉木纯林相比,火力楠与杉木混交可提高土壤活性有机碳含量,但只有土壤水溶性有机碳含量显著提高;各林地土壤活性有机碳具有明显的季节变化,一年中土壤水溶性有机碳含量的大小始终为常绿阔叶林>杉木火力楠混交林>火力楠纯林>杉木纯林,土壤微生物量碳、热水浸提有机碳和碳水化合物则表现为常绿阔叶林>火力楠纯林>杉木火力楠混交林>杉木纯林.与杉木纯林相比,杉木火力楠混交林可提高林地质量,但不同林地活性有机碳的季节变化规律表现不尽一致,表明土壤活性有机碳的季节差异不仅与温度、降雨等气候因素有关,还受到植被类型的影响.

Content and seasonal change in soil labile organic carbon under different forest covers

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.