铅锌废渣场周边土地利用方式转变对土壤胞外酶活性的影响

Effects of land use conversion around a lead-zinc slag heap on soil extracellular enzyme activities

以铅锌废渣场周边7种典型土地利用方式(坡耕地、梯田玉米地、梯田萝卜地、梯田荞麦地、云南松林地、柳杉林地、次生林地)为对象,采用时空互代法研究了铅锌废渣场周边土地利用方式转变过程中土壤养分、重金属含量以及6种土壤胞外酶活性(β-1,4-葡萄糖苷酶、纤维素二糖水解酶、β-1,4-木糖苷酶、亮氨酸氨基肽酶、β-1,4-N-乙酰葡萄糖苷酶和酸性磷酸酶),同时分析了环境因子与6种土壤胞外酶酶活性的相关关系。结果表明,坡耕地转化为其他土地利用方式过程中,土壤中有机碳、全氮、全磷、硝态氮和铵态氮含量呈上升趋势。胞外酶活性基本呈现一致的规律性,表现为次生林地、云南松林地和柳杉林地高于梯田菜地,高于坡耕地。坡耕地转变为次生林地、梯田萝卜地和梯田玉米地,有助于降低土壤中Zn含量;除梯田玉米地和云南松林地外,当坡耕地转变为其他土地利用方式后,土壤中Cu含量显著降低。此外,相较于重金属,土壤养分(有机碳、总氮和铵态氮)对土壤胞外酶活性有着更大的影响,是酶活性变化的主要驱动因素。

In this study,seven typical land use types around a historical lead-zinc slag heap were selected as the research objects,including sloped farmland,terraced corn field,terraced radish field,terraced buckwheat field,Yunnan pine forest,Cryptomeria fortunei forest,and secondary forest.The soil contents of nutrients and heavy metals and the activities of six extracellular enzymes(β-1,4-glucosidase,cellobiohydrolase,β-1,4-xylosidase,β-1,4-N-acetylglucosaminidase,L-leucine aminopeptidase,and acid phosphatase)were examined using space-for-time substitution.We analyzed the relationship between environmental factors and extracellular enzyme activities.The results showed that soil nutrients(organic carbon,total nitrogen,nitrate nitrogen,ammonium nitrogen)increased after sloped farmland was converted to other land use types.The activities of six extracellular enzymes exhibited a similar pattern,which were higher in secondary forest,Yunnan pine land,and C.fortunei forest than those in terraced radish field and lowest in sloped farmland.The conversion of sloped farmland to secondary forest,terraced radish field or terraced corn field could reduce soil Zn content.Soil Cu content significantly decreased when sloped farmland was converted to other land use types,except for the terraced corn land and Yunnan pine forest.Compared with heavy metal pollution,soil nutrient(organic carbon,total nitrogen,and ammonium nitrogen)contents showed a greater influence on soil extracellular enzyme activities,being the major factors driving changes in enzyme activities during land use conversion.