Effects Of Long-term Fencing Closure On Soil And Vegetation In Mountain Pasture Of Bayanbulak

Grassland degradation has caused some serious environmental and social problems in China, which is also the main constraint for grassland utilizing and sustainable development of economy in arid and semi-arid areas. In order to find the causes, mechanisms and ecological processes of grassland degradation and to work out reclamation measures, this paper chooses a long-term fencing mountain pasture managed by the Academia Sinica Bayanbulak Ecology Station as field spots, studies the development mechanism of fragible environment, the disturbance factors, species composition, community structure, species diversity and ecological process of vegetation restoration of grassland of the three lawn types which are Sub-alpine prairie, Sub-alpine prairie meadow and Sub-alpine meadow prairie respectively by field investigation and laboratory analysis. Results are as following.Firstly, fencing improved the plant diversity, community structure and the ecosystem function significantly. From the view of community structure, the grass inside fence was higher than outside, and the average height increased from 10.21cm to 36.75cm, the average coverage increased from 32% to 68%. The ouside Margalef's Index and Shannon—Wiener Index were more than inside, the inside Alatalo Index was more than outside. The grass yield was up from 30.67Kg/hm~2 to 333.34Kg/ hm~2.Secondly, fencing improved the soil physical and chemical properties significantly.The average organic matter content inside fence increased 16.75% in the surface layer. The average total nitrogen inside fence was 28.43% more than that of outside, the average available nitrogen content inside was 17.39% more than that of outside. The total phosphorus and available phosphorus and total potassium contents have no significant difference between inside and outside fence. The variation of soil pH was not significantly between inside and outside fence, both were weak alkali. The average soil volume weight was 0.82g/cm~3 inside fence and 0.91 g/cm~3 outside in 0-20cm surface soil, and the outside was 10.78 percent more than inside.Thirdly, long-term fence increased the quantity of microorganism inside significantly, and the percentge of soil bactera accounted for the main party in the soil microorganism composition, next was actinomycete, the fungi was the least. The surface layer was higher than the lower party in the vertical distribution of the soil microorganisms and it gradually decreased along with soil depth. No matter inside and outside the fence, the characteristics of soil microorganism had obvious relevance with soil physical and chemical properties. Fouthly, long-term fence increased soil enzyme activities inside fence of three kinds of pasture,and the four kinds of soil enzyme activities were remarkable discrepancy inside and outside fence. The trends of soil enzyme activities in the same profile were very similar except for urea enzyme and the surface layer is higher than the lower party.Finaly, soil enzyme activities had a very close relationship with soil physico-chemical properties such as water content, soil organic matter, available N, P and K. The enzyme activities of Urea enzyme, surase enzyme and hydrogen peroxidase had a very close relationship with microbial biomass except for phosphatase enzyme.