Distribution Characters Of Vegetation Coverage And Soil Erosion In Wenanyi Watershed On Loess Plateau

Vegetation is an indispensable part of terrestrial ecosystem, and the increase of vegetation coverage could effectively slow down the occurrence of soil erosion. Watershed is the basic unit for soil and water conservation control, thus enhancing the soil and water conservation monitoring at watershed scale is a very important issue in the field of soil and water conservation at present. Compared with traditional research methods, remote sensing technology has a significant advantage to achieve the quick and dynamic monitoring of watershed vegetation coverage on Loess Plateau. According to the inter-disciplinary theories such as physical geography, geomorphology, landscape ecology, soil and water conservation, mathematical statistics and RS/GIS technology etc, by taking Wenanyi watershed in the hilly and gully region on Loess Plateau as the research object, the characters of vegetation coverage and soil erosion distribution in Wenanyi watershed was studied in the paper. The main conclusions are as follows:Firstly, it proposed a simple and practical way to determine the dimidiate pixel-based model for the vegetation coverage parameters. i.e. NDVIsoil & NDVIveg; By using Landsat TM image data, an improved calculation model of watershed vegetation coverage based on the NDVI vegetation index was constructed, and process for calculating watershed vegetation coverage calculation was proposed in the paper.Secondly, the temporal variation and spatial distribution of watershed vegetation coverage in Wenanyi watershed during pre and post the implementation of the policy of returning cultivated land into forest and grass were monitored and analyzed comprehensively. The results showed that vegetation coverage in Wenanyi watershed on the rise in general over the past 10 years; Vegetation coverage of each year along with a declining trend in higher elevations; Vegetation coverage decreased with the increase of slope; Vegetation coverage of each aspect was on the rise, and North Slope is relatively high while south slope is relatively low, Vegetation coverage of each year and each aspect show the same laws, i.e. north> northwest> northeast>east> southeast>west>southwest> south>flat.Thirdly, it revealed the distribution characteristics of soil erosion in the watershed. The results showed that the main erosion type of Wenanyi watershed is water erosion; The elevation characteristics of spatial distribution of water erosion with various intensities exhibits peak phenomenon, and the distribution above light erosion was concentrated on the region with the altitude about 1000-1100m; Influences of slope gradient on soil erosion were not a single direct proportional correlation;The aspect characteristics showed double-peak structure.At last, the paper discussed the relationship between vegetation coverage and soil erosion. The results showed that, on elevation scale, vegetation coverage was negatively correlated with soil erosion intensity; In the 0-20°slope range, with the slope increased, vegetation coverage was also negatively correlated with soil erosion intensity, while within the framework of greater than 20°, vegetation coverage and soil erosion intensity along with a declining trend in higher slope; In the aspect scale, the changes of vegetation coverage had less effects on the changes of soil erosion intensity.