The Effect Of Different Grassland Communities At Winter-spring Pastures Around Qinghai Lake Drainage Basin On Grazing Time

Taking the grazing time as the research object and doing trails on grasslands ofGangcha county Hargai town that located in Qinghai lake basin,which were dividedinto fore forms included mesotherm grassland,abandoned grassland(abandonedplough in the1960s),alpine steppe and alpine meadow. Two grazing time includedgrazing from grass mature time to seedling (To avoid the sensitive period of growthand development of forage breeding) and conventional grazing were setted up.Continuously recording coverage of grassland community, the important value,diversity, aboveground biomass in two grazing periods. Exploring the feasibility ofgrazing grassland degradation time to remission of grassland degeneration.Thefollowing main results can be concluded through the research:1. The grazing grassland community coverage in fore grasslands which wasavoiding the growth sensitive period are significantly higher than those conductingconventional grazing time. The meadow community under the change of grazing timehave appeared a growth period, in which the community coverage of the mesothermgrassland,alpine steppe and meadow significantly increased that had positive meaningto grassland community protection;2. The grazing time has little impact on grassland community species compositionof mesotherm grassland,while it improved the occupation of dominant species ofAchnatherum. Abandoned land has responded strongly to grazing pastures time,dominant species, the second dominant species and the main accompanying speciescomposition and important value has changed. The response of alpine grassland tograzing time is relatively strong, which is mainly reflected in the change of thedominant species, Leymus and Poa annua under conventional grazing time to formthe dominant species,while the subdominant species in avoiding sensitive growthperiod grassland was covered with Elymus nutans and Poa annua. The response ofAlpine meadow grassland to grazing time mainly manifested in the dominant speciesand the main accompanying species, especially after the grazing time changed, Agropyron cristatum has become the subdominant species in community bringsignificant meaning to grassland production;3. The grazing time could change the community richness of the Magalef in alpinesteppe and the Pielou uniformity of the abandoned land significantly, while hasirregular effects on other community.The vegetation Shannon Wiener diversity effectwas not obvious;4. Grazing in the time avoiding the growth sensitive period could makecommunity aboveground biomass fresh weight significantly higher than grazing onconventional time. However, the influences to different grassland communities aredifferent, alpine meadow, alpine steppe and abandoned land pasture has increasedobviously except mesotherm grassland;5. The Cluster analysis showed that: abandoned grassland and alpine grasslandwas similarity. It is highly possible that the abandoned grassland was alpine grasslandbefore it was used.