Advances on soil enzymatic activities in grassland ecosystem

Soil enzymes play an important role in the soil ecosystem nutrient cycling and energy flow．Therefore, the study of soil enzymatic activities has important significance to investigate the structure, function and sustainable development of grassland ecosystem．The research of soil enzymes has experienced three different historical periods which were foundation period(Before 1950s), fast development period (1950-1980s) and mutual penetration with other disciplines period (1980s)．Soil enzymes are mainly derived from soil microbe. They can be divided into six categories which were oxidoreductase, hydrolase, transferase, lyase, ligase and isomerase．This paper summarizes several factors affecting soil enzymatic activities of grassland ecosystem, such as degradation levels, fertilization, grazing, soil microbe, season and so on．Based on previous research, we concluded that: 1) soil enzymatic activities tend to decrease with the aggravation of degradation, 2) soil enzymatic activities could be increased to some extent by fertilization, 3) soil enzymatic activities increased by light grazing but reduced by heavy grazing, 4) soil enzymatic activities positively correlated with soil microbe, 5) soil enzymatic activities varied with season. Finally, a prospect to the research and development of the relationship between degradation, restoration and improvement of QinghaiTibet plateau alpine meadow ecosystem and soil enzymatic activities was made.