Effects Of Rest-grazing In Green-up Period On Alpine Grassland Plant Community And Soil Characteristics

As an important grassland ecosystem and grazing ecosystem in my country,the alpine grassland on the Qinghai-Tibet Plateau plays an important role in environmental protection and regional economic development.The rapid increase in the number of grazing livestock caused by population growth has led to further expansion of the damage to the grassland by grazing,problems such as grassland degradation have emerged.In order to explore the effects of rest-grazing on the plant community and soil physical and chemical properties of the alpine grassland in northwestern Sichuan,and to explore effective and feasible methods for the restoration of degraded grasslands,this study set up a typical alpine grassland in Hongyuan County,Aba Prefecture,Sichuan Province,on the southeastern edge of the Qinghai-Tibet Plateau.3 different grazing treatments(control: whole year’s rest-grazing;traditional grazing: grazing from the end of May to September,the grazing intensity is 3 yaks/ha;rest-grazing in green-up period: grazing from the end of June to the end of September,the grazing intensity is 3 yaks/ha).Mainly studied the effects of rest-grazing in green-up period on the coverage of plant communities and family genera,biomass,underground biomass,species diversity,and soil physical and chemical properties.The main results are as follows:1.The whole year’s rest-grazing and rest-grazing in green-up period significantly improved the total coverage of the community and the sub-coverage of the Poaceae(P<0.05).There was no significant effect on the coverage of Cyperaceae,Fabaceae,Asteraceae and Others(P>0.05).2.The whole year’s rest-grazing significantly increased the total biomass of the community and the biomass of Poaceae and Others(P<0.05);while rest-grazing in green-up period and traditional grazing significantly reduced the biomass of Others(P<0.05),no significant effect on the biomass of Cyperaceae and Asteraceae(P>0.05);below-ground biomass has no significant response to rest-grazing(P>0.05).3.Rest-grazing in green-up period has no significant effect on Pielou evenness index and shannon-wiener diversity index(P>0.05),while the rest-grazing in green-up period significantly increased the number of species(P<0.05).4.Rest-grazing has no significant effect on the soil moisture content(P>0.05),and has no significant effect on the soil bulk density of the 0-10,10-20 cm soil layer(P>0.05),while in the 20-30 cm soil layer the soil bulk density was significantly reduced in rest-grazing in green-up period(P<0.05).5.The whole year’s rest-grazing and rest-grazing in green-up period have no significant effect on the organic carbon in the 0-20 cm soil layer(P>0.05),and significantly increased the organic carbon content in the 20-30 cm soil layer(P<0.05).Rest-grazing treatments had no significant effect on the pH value of 0-20 cm soil layers,while the pH value of traditional grazing soil was significantly higher than the whole year’s rest-grazing(P<0.05).Rest-grazing increased the total nitrogen content of0-10 cm and 10-20cm(P>0.05),reaching a significant level in the soil layer of20-30cm(P<0.05);rest-grazing had no significant effect on the total phosphorus content of the soil(P>0.05);the whole year’s rest-grazing significantly increased the total potassium content of the soil(P<0.01).The available nitrogen content of the rest-grazing in green-up period is extremely significantly higher than the whole year’s rest-grazing sample plot in the 0-10 cm soil layer(P<0.01),and significantly higher than the traditional grazing sample plot(P<0.05),The rest-grazing in green-up period plot in the 10-20 cm soil layer was significantly higher than the whole year’s rest-grazing plot(P<0.05),The rest-grazing in green-up period was significantly higher than traditional grazing in the 20-30 cm soil layer(P<0.05).The available phosphorus content in the three soil layers is the rest-grazing in green-up period plot is significantly higher than the whole year’s rest-grazing plot(P<0.01),the 0-20 cm soil layer whole year’s rest-grazing plot is significantly lower than the traditional grazing(P<0.05).The content of soil available potassium in the rest-grazing in green-up period plot was extremely significantly higher than whole year’s rest-grazing plot(P<0.01).The 0-10,20-30 cm soil layer rest-grazing in green-up period plot is significantly higher than the traditional grazing plot(P<0.05)There was no significant difference between the whole year’s rest-grazing plot and traditional grazing(P>0.05).There is no significant difference in soil C/N,C/P and N/P in 0-20 cm soil layers(P>0.05).The C/N of the 20-30 cm soil layer in the traditional grazing plot was significantly higher than the rest-grazing in green-up period(P<0.05),and the C/P and N/P in the rest-grazing plot were significantly higher than those in the traditional grazing plot(P<0.05).