Abstract: 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.

Key words: land use conversion, enzyme activity, soil nutrient, heavy metal.