Abstract: Taking a mown Leymus chinensis meadow in Hulunbuir as the research object, we studied soil microbial response and microbial relationship under different shortterm fertilization treatments by measuring soil microbial quantity, microbial biomass and enzyme activity. Results showed that: (1) Fertilization significantly increased the quantity of soil fungi. With increasing fertilization levels, the quantity of fungi and actinomycetes showed an increasing tendency, but the bacterial quantity decreased. (2) Fertilization significantly increased soil microbial biomass carbon and microbial quotient, while the microbial biomass nitrogen, soil sucrase, urease and catalase were not significantly affected. (3) The soil fungi quantity was significantly positively correlated with soil microbial biomass carbon after fertilization, and the bacterial quantity was significantly positively correlated with the quantity of actinomycetes. (4) Low fertilization level (N 3.5 g·m^-2+P 1.7 g·m^-2) was suitable for the growth of soil microorganisms. A close relationship was found between the soil microorganisms after fertilization. Microbial quantity was the most sensitive to short-term fertilization, secondly was the enzyme activity and microbial biomass. The fungi had more sensitive response to fertilization.

Key words: agro-pastoral ecotone in Northern China, environmental effect, land use/cover change (LUCC), driving force