Soil quality is a synthesis of many physical, chemical and biological properties of soils and of some important processes
of forming these properties 〔1〕 . The biological properties of soils can sensitively reflect the change of the soil quality and health 〔2〕 . Therefore, it is increasingly paid an attention to that the parameters of soil biological properties, such as the microorganism biomass, composition of microorganism communities and their biodiversity, and active enzyme, are used to characterize the change and dynamics of soil quality 〔2～5〕 . The research on the desertification evolution of the physicochemical properties of farmland soils has been carried out in Horqin Sandland where desertification is serious 〔6〕 . This paper analyzes the desertification evolution of the biological properties of soil quality by researching the
activation of soil enzyme and of basal soil respiration in the rainfed farmland of Horqin Sandland in the
desertification process. The results show that the response of the activation of soil enzyme and the basal soil respiration are sensitive to the environmental change in the desertification process. The activation of catalase, urease and alkaline phosphatase related to the soil physicochemical fertility factors and the basal soil respiration are reduced with the increase of the desertification degree. The soil enzyme activation and respiration activation have a strongly positive correlation with the soil organic matter and the content of N and P nutrients, and, therefore, can be regarded as the important supplementary indicators of the change of soil quality properties in the desertification process.