Study on the Degrading Process and Character of Community of Natural Grassland in Crisscross Part of Qinzang and Loamy Plateau——Taking Baiyin City of Gansu Province as an Example

The constitution of the flora,type and structure of the grassland,plant amount and the vegetation coverage and biomass on the degraded grassland in Baiyin City of Crisscross Part of QinZang and Loamy Plateau were studied and analyzed.The varying regularity in space of structure and character of vegetation in different degrading period on nature grassland was also studied.With the severity of degeneration of grassland,from initial stage to latter period,the plant in perch-bud first disappeared,the plant amount of vegetation community and the density of predominant plant were declined sharply.The converage,biomass and the proportion of the yield fresh grass to edible grass have also declined rapidly.In the end,the way was suggested in order to protect ecologic environment on natural grassland.