三峡库区不同林龄柑橘土壤酶活性的演变

土壤酶驱动土壤生态系统养分的循环和控制生态系统的功能。本研究以生长年限为10、20年和30年的柑橘林0~20 cm和20~40 cm土层土壤为研究对象,主要探讨了土壤脲酶、转化酶和过氧化氢酶活性随着柑橘林龄的延长和土壤深度的增加的变化规律。结果表明,随着柑橘林龄的延长,0~20 cm土层土壤过氧化氢酶活性10年和20年样地之间无显著性差异,但都显著大于30年的样地;而0~20 cm土层土壤转化酶和脲酶活性逐渐提高,20年时达到最大值,其后又降低。随着土壤深度的增加,过氧化氢酶、转化酶和脲酶活性在3个林龄的柑橘林中都呈现显著的下降趋势。相关性分析的结果表明,土壤转化酶活性、脲酶活性都与土壤有机碳和微生物量碳氮之间都具有显著的正相关性,而过氧化酶氢活性与土壤理化特性及其微生物量之间都无显著的相关性。主成分分析结果进一步显示,土壤转化酶活性、脲酶活性、有机碳和微生物生物量碳氮均在第一主成分中具有较大的载荷,对第一主成分的贡献最大。以上结果表明脲酶和转化酶活性能够做为柑橘土壤质量变化的敏感指标。

Changes in Soil Enzyme Activities at Different Ages of Citrus Stands in Three Gorges Reservoir Area,China

Soil enzyme catalyzes soil nutrient cycles and control the function of ecosystem. The changes in activities of catalase, invertase and urease in 0~20 cm and 20~40 cm soil depths were determined at different ages(ie. 10-, 20-, and 30-years old)of citrus stands in Three Gorges Reservoir Area. The results showed that catalase activity in 0~20 cm soil depth were lower in 30-year-old than those of 10- and 20-year-old sites which had no significant difference. Invertase and soil urease activities in 0~20 cm soil depth increased gradually, and tende to be highest under 20-year old site, and thenafter it decreased again. Soil catalase, invertase and urease activities decreased with soil depth at each citrus stand age. Soil urease and invertase activities showed significant relationship with soil organic C, microbial biomass C, and micro-bial biomass N whereas soil catalase activity had no significant relationship with soil physical, chemical and microbial properties. The results of principal components analysis showed that invertase activity, urease activity, organic C, microbial biomass C, and microbial biomass N were the major contributors in the first principal component due to more high factorial loads. Therefore, the results indicated that soil urease and invertase activities might be sensitive indicators for the change in soil quality in citrus stand.