Analysis Of Alpine Grassland Pasture Utilization Status Based On Low-altitude Remote Sensing

Overgrazing has a serious impact on the ecological environment of the Zoige alpine grassland and the production and life of herdsmen.The research on the status quo of pasture utilization based on low altitude remote sensing can provide certain theoretical basis and technical reference for pasture monitoring in alpine grassland.The research method of pasture utilization with high efficiency,high accuracy and low cost is of great significance for regulating grazing behavior and healthy and sustainable development of grassland ecological resources in Zoige alpine grassland.In this study,a small winter pasture in AMu township,HongYuan county,was used as the research experimental area.First,UAV was used to obtain aerial camera pictures of the experimental area,and the low altitude remote sensing ortho image of the area was obtained through processing.Secondly,three methods,vegetation index method based on threshold,remote sensing estimation model of biomass,and object-oriented scale segmentation,were used to extract the grassland information and herd quantity information of the image in the study area,and evaluate the accuracy of the extraction results.By analysis and comparison of different research methods,the best extraction method of grassland information and herd quantity information in this area is finally obtained,and the utilization status of the pasture is analyzed with the obtained method.The main research conclusions are as follows:(1)Compared with 11 kinds of visible vegetation index,the method of histogram entropy threshold,OTSU method and sample based threshold method are used to extract grassland information.V-MSAVI combined with sample based threshold method has the highest overall accuracy of 95.50%,and kappa coefficient is 0.8534,which is an effective method for extracting grassland information in Zoige alpine grassland.(2)Among the polynomial regression models constructed by the measured biomass and11 visible light vegetation indexes,the NGRDI model has the highest accuracy and the smallest error(R~2=0.8864,MAE=8.969 g/m~2,RMSE=9.703 g/m~2),which is the model method with the highest accuracy for biomass estimation in Zoige alpine grassland.(3)The accuracy rate of the object-oriented scale segmentation method to extract the number of herds is 94.74%,the wrong fraction rate is 3.57%,the missing fraction rate is5.26%,and the extraction accuracy is high,which is an effective method to extract the number of herds in the Zoige alpine grassland.(4)The pasture and grassland area in the study area accounts for 66.72%of the total pasture area in the study area,and the non-grassland area accounts for 33.28%of the total pasture area.The grassland coverage rate is relatively low,which is dominated by the low-coverage grassland with the coverage less than 40%,and the above-ground biomass of the grassland below 80g/m accounts for 96.96%of the total study area.~2The winter climate and environmental factors in the alpine grassland have an impact on the growth of herbage.The characteristics of the surface frozen soil are obvious.At this time,the height and coverage of herbage are at a low level in a year.In the non-grassland and low biomass areas,the main surface features are the frozen earth mounds,bare land and the withered and yellow grassland,which are in line with the characteristics of the winter pasture.(5)The pasture is located in the Zoige alpine grassland,with a total area of 128.5hectares.The grazing animal is yak,and the extraction result of herd quantity is 167.During this period,the grazing intensity of the pasture was 1.3,which was in an overgrazing state,and the above-ground biomass of the grassland could bear grazing activities for up to 22days.In order to ensure the reasonable use of the winter pasture,grazing activities should be transferred from the winter pasture to the summer pasture in mid-may.