Research On The Relations Between Topographic Variables And Distribution Of Saline Soil And Vegetation

Soil salination often occurs in these area, where the climate is drought, the soil's evaporation is very intensity, and the water table is high and contain high dissolubility salt. It was occurred by certain climate, terrain, and hydrogeology, and they together influenced the water and salt movement. Combine terrain analysis which based on DEM with RS technic could provide service and guidance with multi-arid scale, high updating frequency and high estimate precision.This paper takes the Delta Oasis of Weigan and Kuqa Rivers as study area.Firstly, this paper give expression to the spatial change of the study area by calculating five kinds of topographic information: elevation, slope, aspect, topographic relief and topographic wetness index based on DEM, and then analyse macroscopical topographty characters, elevation statistic characters, topographic relief and effect of DEM interpolation on the slope.Then, take the planet datas of 2007 as basic data source, we get the distribution informations about the soil salinity with supervised classification methods and NDVI data, which give expression to the status of land salinization and vegetation. At last, combine all of the topographic informations with classication results and NDVI, I analyse the relationship between saline land and elevation, slope, aspect and topographic relief, and the correlation between NDVI and slope, aspect, TWI. Conclusions can be drawn that:1. Analysis of topographty characters based on DEMElevation statistic characters: the main surface feature of the study area is plainness, the altitude is between 947 m -1050m; the terrain is degression from northwest to south- heast, and there is no break on the surface.Spatial distribution characters of topographic relief: according to the result of calc- ulation, the best size of statistic unit is confirmed to be 20×20(600×600㎡).2. Spatial differentiation of the saline land and mutiscale analysis of vegetation index and topogeraphic variablesElevation, slope, aspect and topographic relief has less influence on mild\moderate salinity soil; elevation, slope and topographic relief has distinctness influence on severe salinity soil without aspect.Correlations between NDVI and elevation, slope, SI, EI, TWI were identified by the Spearman non-parametrical method, Moran's I coefficients were also calculated for all selected variables, which indicate that: on the non- saline land, topographic is not the leading action on water\salt moving; on the saline land, correlations between NDVI and elevation were highly significant at all scales, at the 600m grain scale, the correlation coefficients between slope were become significant.