Degradation Of Grassland In Shangri-La Based On Remote Sensing Technolgy

The grassland resource is the basis of husbandry and tourism.But with the changing of natural environment and the development of social economy,grassland has undergone degradation of different degrees.As the priority in the treatment of grassland degradation is to clarify its distribution range and degradation degree.remote sensing technology plays an important role in grassland degradation research.By taking Xiaozhongdian Town and Jiantang Town in Shangri-La as research area using the data of HJ-1 satellite as data source,combin with filed investigation,to construct a remote sensing monitoring model based on vegetation index,the research on 2008-2017 grassland degradation in the area was carried out with the support of geographic information technology,in an attempt to provide scientific data and prevention and control measures for grassland degradation monitoring and degraded grassland remediation.The main research contents and results are as follows:(1)Construction of grassland degradation index.The Grassland Degradation Index(GDI)was calculated by using the grassland vegetation coverage,above-ground biomass,altitude,species richness,edible grass biomass and toxic weeds ratio.The GDI value obtained in the research was between 0.165 and 0.782.The optimal segmentation algorithm in cluster analysis is utilized to divide GDI into four levels indicating the degrees of grassland degradation.The categories are:1)GDI>0.516,non-degradation;2)0.375<GDI?0.516,light degradation;3)0.256<GDI?0.375,moderate degradation;and 4)GDI<0.256,serious degradation.(2)Construction of remote sensing model of degraded grassland.HJ-1 satellite was taken as date source.Analyze 4 bands of information and seven common vegetation indexes(NDVI,DVI,RVI EVI,PVI,RDVI,and SAVI)were extracted after pre-processing and analyzed with GDI on correlation.The superior correlation index RVI was selected to construct the linear regression model with GDI.The remote sensing inversion criteria of grassland degradation grade were obtained through constructing inversion model.They are:1)non-degradation,RVI>5.289;2)light degradation,4.007<RVI?5.289;3)moderate degradation,2.875<RVI<4.007;4)serious degradation,RVI<2.875.(3)Spatio-temporal layout changes of grassland degradation.The land use classification was carried out in the study area by using the HJ-1A/B satellite remote sensing image,and then remote sensing monitoring model of degraded grassland was use to analyze the temporal and spatial changes of grassland in the study area from2008 to 2017.(1)The grassland area in the study area presented a continuous decreasing trend,with 66.53 km~2 of grassland area reduce in the past decade.The type of grassland was mainly transferred into cultivated land and construction land,concentrating near the urban area of Jiantang Town.(2)Change in degradation intensity.The non-degradation area decreased by 59.87 km~2 from 2008 to 2017 with a decreasing rate of 6.65 km~2/a;the light degradation area decreased at an average speed of 5.44 km~2/a during the research period;moderate degradation area increased by 41.17 km~2 in total during monitoring,with a fastest growth in 2008-2013 at 6.56km~2/a.While serious degradation area saw little changes with long-term stability.(3)Spacial distribution.The grassland in study was scattered,mainly concentrating in the center of the study area,distributing north-south in narrow strips.It presented a pattern of spreading from center to the outside with serious-weak-serious grades.(4)From the perspective of degradation(deterioration)and restoration of degraded grassland,its changing in monitoring was featured with deteriorating,with an increased degradation area of 111.50 km~2 in 2008 to 2017,far more than restoration area of 30.73 km~2/a.The current situation of grassland degradation gives no reason for optimism.(4)Countermeasures.The research suggests that the main factors leading to the degradation of grassland are overgrazing,less rain,toxic weed invasion and tourist destruction.Among them,human activities directly affect grassland ecological security.In order to maintain the healthy development of natural grassland,in future grassland treatment we should pay attention to:precise area selection and targeted treatment;artificial removal of toxic weeds,increasing artificial grassland and its production,reducing the number of large livestock,and regulating Tibetan pig breeding,so as to ease the grass-livestock contradiction;improving tourists'awareness of protecting grassland,and strictly prohibiting littering and destroying grassland.