Effects of soil nutrient and soil microbial biomass on soil enzyme activities in abandoned croplands with different restoration age

In order to make a better understanding on the effects of soil nutrient and soil microbial biomass on soil enzyme activities under erosion environment,long-term located farmland with an abandoned age sequences of 0,1,5,7,10,15,20,25,30,40,and 50 years in Zhifanggou watershed (8.27km2 ),Shaanxi Province were studied,which was a typical erosion environment on loess hilly region. The coupling relationships among indexes of soil enzyme with soil nutrient and microbial biomass were analyzed by using stepwise and nonlinear regression. Soil enzyme activities had a significant correlation with soil fertilizer and soil microbial biomass except α-amylase (P0.05). For soil enzyme activities and soil fertilizer factors,Urease (URE) and cellulase (CEL) were affected by total N,alkaline phosphatase (ALP) and catalase (CAT) were affected by available N,saccharase (SAC) and polyphenol oxidase (PPO) were affected by available N and organic matter. For soil enzyme activities and soil microbial biomass,Urease (URE) was affected by soil microbial biomass P; alkaline phosphatase (ALP),catalase (CAT),saccharase (SAC) and polyphenol oxidase (PPO) were affected by soil microbial biomass C,cellulase (CEL) was affected by soil microbial biomass N. However,polyphenol oxidase (PPO) decreased with the increase of available N,organic matter and soil microbial biomass C. There was a significant logarithmic relationship among those indexes (y=b+alnx,P0.05).