Abstract: Soil enzymes are the specific biological catalysts for biochemical reaction in soil, and one of the indicators of evaluating soil health. This study was conducted at the grasslands in the western slope of the Helan Mountain and its piedmont in Alxa, Inner Mongolia, China. With measuring the distribution characteristics of soil enzyme activities, the relationships between soil enzyme activities and soil, vegetation and climatic factors were studied. The results are as follows: (1) Soil enzyme activities were decreased with the decrease of altitude and in an order of alpine meadow > mountain steppe > mountain desert steppe > steppe desert, and the difference was significant in topsoil (0-10 cm in depth); (2) Soil enzyme activities were decreased with the increase of soil depth; (3) According to the partial correlation and stepwise regression analysis, the main factors affecting the activities of soil urease and saccharase were soil microbial biomass carbon, soil organic carbon and total nitrogen, soil alkaline phosphatase activity was mainly affected by soil microbial biomass carbon and total nitrogen, and soil catalase activity was mainly affected by soil microbial biomass, total nitrogen, pH value and precipitation.

Key words: grasslands, soil enzyme activity, altitude, soil microbe, Helan Mountain, Alxa