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在我国南方,天然次生阔叶林转变为杉木人工林是一种常见的管理措施.为研究森林利用方式转变对土壤微生物量的影响,我们在中国科学院会同森林生态实验站比较了天然次生阔叶林、第一代和第二代杉木人工林土壤理化性质和微生物量.杉木人工林土壤有机碳、全氮、铵态氮和微生物量碳氮含量明显低于天然次生阔叶林.第一代、二代杉木人工林土壤微生物量碳仅为天然次生阔叶林的53%和46%,微生物氮为97%和79%.杉木人工林土壤微生物量碳占有机碳的比例也低于天然次生阔叶林土壤,但微生物量氮则相反,为杉木人工林高于天然次生阔叶林.因此可以得出,天然次生阔叶林转变为杉木人工林以及杉木林连栽引起了土壤生物学特性和土壤质量降低.图2表3参36.“,”Conversion of natural secondary broad-leaved forest to Cunninghamia lanceolata plantation is a common management practice in subtropical China. In this study, we compared soil physico-chemical properties, microbial biomass in one natural secondary broad-leaved forest and two C. lanceolata plantation sites to estimate the effects of forest conversion on soil microbial biomass at the Huitong Experimental Station of Forestry Ecology, Chinese Academy of Sciences. Concentrations of soil organic carbon, total nitrogen, NH4+-N and microbial biomass carbon and nitrogen were much lower under C. lanceolata plantations as compared to natural secondary broad-leaved forest.Soil microbial biomass C in the first and second rotation of C. lanceolata plantations was only 53%, 46% of that in natural secondary broad-leaved forest, and microbial biomass N was 97% and 79%, respectively. The contribution of microbial biomass C to soil organic C was also lower in the plantation sites. However, the contribution of microbial N to total nitrogen and NH4+-N was greater in the C. lanceolata plantation sites. Therefore, conversion of natural secondary broad-leaved forest to C. lanceolata plantation and continuous planting of C.lanceolata led to the decline in soil microbial biomass and the degradation of forest soil in subtropical China.