Research On The Relationship Between Topographic Factors Of Plateau Sand Slopes And Vegetation Restoration Based On 3D Point Cloud

Grassland degradation and land desertification are serious problems in Tibetan plateau area because of climate change.Plateau area has a high altitude,a cold and arid climate and a fragile ecological environment,which bring many difficulties to improve the desertification environment.Environmental workers have carried out vegetation restoration in plateau sand slopes to improve the ecological environments.In order to explore how topography influences the vegetation restoration,it is necessary to investigate the topography of plateau sand areas and understand the growth condition and distribution of vegetation.The traditional investigation method is mainly based on field investigation.This kind of method is time-consuming and labor-consuming,and the investigation results are not precise enough.In this paper,we obtained high-precision Digital Elevation Model(DEM)and vegetation point cloud from 3D point cloud data,and accurate terrain information and vegetation features were obtained from DEM and vegetation point cloud separately.The relationship between topography and vegetation restoration was explored by utilizing terrain information and vegetation features.The 3D point cloud data has characteristics of high precision,high density and it can be obtained in a short time.In this paper,we took advantages of point cloud data,extracted topography information and vegetation information of the study area,and analyzed the relationship between the topography and vegetation restoration.The research work that this paper completed is as follows:(1)The obtained 3D point cloud data of the study area was utilized to generate highprecision DEM and extract slope,aspect,Topographic Wetness Index(TWI)from the DEM.In this study,we first selected a filtering method,which is suitable for the topography of the study area,to finish filtering point cloud,and the ground point cloud was extracted.DEM then was generated by using ground point cloud and Triangulated Irregular Network(TIN)interpolation algorithm.By using the Arc GIS software to process DEM,several topographic factors were obtained,including slope,aspect and TWI.(2)When vegetation point cloud was extracted from the original point cloud data and it was processed with Li DAR360 software,features of vegetation in the study area could be obtained.Firstly,the original point cloud was normalized by DEM,which can eliminate the influence of topographic relief.Secondly,the normalized point cloud was filtered to obtain non-ground point cloud.Thirdly,the non-ground point cloud was clustered into different point cloud blocks,and vegetation point cloud could be extracted by selecting point cloud blocks that satisfied the given constraints.Finally,parameters of vegetation features were calculated by using Li DAR360 software and the corresponding calculating methods.(3)According to the obtained topographic factors and vegetation features,the relationship between topography and vegetation restoration was analyzed.In this paper,we delineated 10 plots in the study area and acquired topographic information and vegetation information of these plots.Relationships between topography and vegetation restoration in each plot were analyzed generally,and influences of the elevation,slope,aspect and TWI on vegetation distribution were analyzed separately.According to the analysis results,topographic features of areas which had vegetation,and topographic features of plots that were suitable for vegetation growth were both obtained.According to the research work in this paper,the feasibility of utilizing 3D point cloud data to study ecological environments of plateau sand slopes is verified.This study also provides a new approach for environmental workers to conduct research on the relationship between topography and vegetation restoration.