Study On Characteristics Of Grassland Vegetation Community Under Different Grazing Management And Its Relationship With Environmental Factors In Hulunber Grassland

Vegetation degradation in the Hulunber grassland was the main factor restricting the utilization and sustainable development of grassland resources in the arid and semi-arid regions of northern China.In order to explore the impact of different grazing management on the restoration of degraded grassland ecosystems,this study took the "Seven-one" ecological family ranch as the research object in the three animal husbandry banners of Hulunber City(hereinafter referred to as the research area),Xin Barag Zuoqi,Xin Barag Youqi and Chenbarhu Banner.Guided by the restoration of ecological theory,the combination of field investigation and indoor analysis was used to study the vegetation community characteristics such as species composition,community type and community diversity under the four grazing management of grazing-prohibited,rest grazing,rotational grazing and perennial grazing.The relationship between environmental factors and vegetation distribution were analyzed to determine the response mechanism of vegetation community characteristics to grazing management.The results showed that:(1)The total number of species in the rest grazing and rotational grazing areas was greater than that in the grazing-prohibited and perennial grazing areas.The dominant species in different grazing management area were different in three banners,but the Cyperaceae and Gramineae plants were dominant species,among which the important value of Carex duriuscula,Leymus chinensis and Stipa krylovii were the highest.Liliaceae plants such as Allium bidentatum and Allium mongolicum were more distributed in grazing-prohibited and rotational grazing area of Zuoqi and rest grazing area of Youqi Rosaceae plants were more distributed in perennial grazing area of Zuoqi and rest grazing,perennial grazing area of Chenqi.The plants of Asteraceae were widely distributed in rotational grazing area of Zouqi and Chenqi while the Chenopodiaceae plants were widely distributed in grazing-prohibited and perennial grazing area of Chenqi.(2)The vegetation in the study area was mostly annual,perennial xerophytes and medium xerophytes.Two-way indicator species analysis showed that vegetation in Zuoqi can be divided into four community types,vegetation in Youqi can be divided into five community types,and vegetation in Chenqi can be divided into three community types.The communities and associated species were different in different grazing management’s areas.In Youqi and Chenqi,there were more xerophytes in the grazing-prohibited area and the perennial grazing area,and more middle xerophytes in the rest grazing area and the rotational grazing area.In Youqi,xerophytes were mostly distributed in the grazing-prohibited area,while xerophytes were mostly distributed in the perennial grazing area.(3)The changes of vegetation cover and biomass under different grazing management showed that the grazing-prohibited area and rest grazing area were larger than rotational grazing area and perennial grazing area.On the whole,the vegetation coverage and biomass of Zuoqi were the highest,followed by Chenqi,and the vegetation coverage and biomass of Youqi were the lowest.(4)The community diversity index was different according to the grazing management’s method.The variation of community diversity index in the different grazing management of Zuoqi and Chenqi showed that the rest grazing and rotational grazing could significantly promote the improvement of community diversity index.In Youqi,the community diversity index was higher and the community was more stable in the grazing-prohibited area and rest grazing area.On the whole,the vegetation restoration of the Zuoqiwas was better than that of Chen flag,and the vegetation restoration of Youqi was the worst.(5)Through canonical correspondence analysis and rank correlation analysis,the relationship between species distribution,community diversity index and environmental factors was analyzed.Results showed that soil water content,bulk density,compactness and organic matter content were the most important environmental factors affecting species distribution.Soil bulk density and water content were the main environmental factors affected the distribution of species in Zuoqi,and water content and organic matter in Youqi while water content and compactness in Chenqi.Soil water content,electrical conductivity,total nitrogen content and bulk density had significant effects on community diversity index.