Study On The Evaluation Of Grassland Desertification In Qiangtang Plateau

In the context of global climate change and human activities,the alpine grassland desertification is serious increasingly,moreover,the life of the residents is facing unprecedented challenges,therefore,it is of great significance to explore the desertification of the alpine grassland to the economic development of alpine plateau.In our study the remote sensing images from 1984 to 2013 year were analyzed via the method of landscape index,the object is to obtain the spatiotemporal dynamic distribution of desertification in the alpine meadow of Qiangtang plateau and the main driving factors.Meanwhile,the different gradients of the desertification,the driving factors of desertification and desertification restoration were selected to reflect the variation and analyze the internal mechanism of the desertification among biodiversity,above ground biomass,and soil nutrient status.Some results were shown as:(1)Spatiotemporal dynamic distribution of the desertification grassland in Qiangtang plateau;The desertification grassland of Qiangtang plateau mainly distributed in the northern regions of the Qiangtang plateau,which occupied most of the study area.The desertification grassland was improved in the study period,but there is a potential desertification risk in Qiangtang plateau.The human activities were more significant driving factors than the environmental factors in the desertification of the alpine grassland in the Qiangtang plateau.(2)The correlation between the biodiversity,above ground biomass,and soil nutrient status in the desertification.The biodiversity and above ground biomass of alpine grassland increased firstly and then decreased under the desertification gradient in the study area.The soil water content,temperature,total carbon and available nitrogen played positive roles in the alpine grassland but pH.The soil compactness of desertification grassland has a promoting effect on above ground biomass but the biodiversity,and the soil temperature had a passive effect on above ground biomass and biodiversity via the method of direct impacting and the method of indirect impacting which based on the direct effect of the soil total carbon,organic carbon,total nitrogen and total phosphorus.(3)The study of the main driving factors of the desertification of alpine meadowThe main driving factors of the desertification of alpine meadow were the overgrazing and rodent in Qiangtang plateau.The biodiversity and above ground biomass were decreasing under the rodent gradient in the study area.Soil compactness,soil total carbon,total nitrogen and available phosphorus played passive roles in the alpine grassland but soil temperature.The soil compactness had passive effect on above ground biomass but biodiversity,and the soil temperature had a promoting effect on above ground biomass and biodiversity via the method of direct impacting and the method of indirect impacting which based on the direct effect of the total carbon,total nitrogen and available phosphorus.The distribution of rodent depended mainly on the grassland vegetation types.In the study,we obtained that the rodent promoted the above ground biomass but biodiversity and there is a potential risk of desertification.Soil density,soil total carbon,organic carbon,total nitrogen,available nitrogen promoted alpine grassland but soil temperature.The soil compactness had a promoting effect on above ground biomass but biodiversity,and the soil temperature had a negative effect on above ground biomass and biodiversity via the method of direct impacting and the method of indirect impacting which based on the direct effect of soil total carbon,organic carbon,total nitrogen and total phosphorus.In summary,overgrazing had a negative influence on the alpine grassland via the destroying of the above ground biomass and biodiversity.Alpine grassland of the rodent had a potential risk of desertification via the destroying of biodiversity.(4)The internal mechanism of the desertification restoring process and the correlation between the biodiversity,above ground biomass,and soil nutrient statusThe fencing had a non-significant positive effect on the above ground biomass and biodiversity.The soil water content,total nitrogen,and available nitrogen had a certain positive effect on alpine grassland in the Qiangtang plateau.The soil water content had a promoting effect on above ground biomass and the biodiversity but soil temperature via the method of direct impacting and the method of indirect impacting which based on soil total nitrogen and available nitrogen.