Abstract: The impacts of climate change on ecosystems will be expanded in the future. Soil enzyme is one of the active components in grassland soil,and it is closely related to soil nutrient content.In this study,the top-opened growth chambers were used to simulate the temperature increase and rainfall increase in a typical steppe in 2011 so as to explore the response of soil nutrient content and enzyme activity to climate change in semiarid area.The experiment was carried out under four treatments,there are CK (controlled),T (temperature controlled),P (rainfall increased) and TP(both temperature and rainfall increased) respectively.The values of soil nutrient availability and of activity of four enzymes were measured.It was found that the contents of soil nitrate nitrogen and ammonium nitrogen were increased by 40.2% and 129.1% respectively by increasing temperature.The nitrate nitrogen content was increased by 63.5% by increasing rainfall,but the ammonium nitrogen content was decreased by 63.6%.The activities of catalase and sucrose enzyme were decreased by 4.8% and 13.3% respectively by increasing temperature.Contrarily,the activities of alkaline phosphatase,sucrose enzyme and urease were increased by 7.1%,35.7% and 14.9% respectively by increasing rainfall,but there was no significant effect of rainfall increase on catalase (P>0.05).The contents of nitrate nitrogen and ammonium nitrogen were in an increase trend under the interaction of both temperature increase and rainfall increase (P<0.05).The responses of four soil enzyme activities to climate change were different,which may be related to the change of nutrient cycling with climate change.

Key words: climate change, typical steppe, soil nutrient, soil enzyme activity, increase temperature and precipitation, Inner Mongolia