| This research has chosen Jiu Xian Shan watershed in the Yi Meng mountainous area as the study region. 0.25m high resolution images is the main information sources. Use the theory of soil and water conservation, the principle of land suitability as guidance, through the methods of man-machine interaction interpretation and investigation in the open air, environmental factors of watershed, soil erosion situation, the relationship between the environmental factors and soil erosion, land suitability have been analyzed and evaluated. And the main results are as follows:1. The environmental features of watershed is expounded.The watershed is like a dustpan form north to southward, the elevation of watershed is between 96.2m and 548.2m, watershed length is 4.12km, and the width is 2.19km, integrity coefficient of watershed is 0.53. The total length of the gully in watershed is 33.84km, gully density is 3.75km/km2, the average ditch slope is 3.40%; landscape is mainly in hilly, the landforms is mainly gentle and steep slope gradient level. Brown soil is the main soil,soil depth, soil physical characteristics and soil chemical characteristics is spatial variability.Soil layer thickness is between 10cm and 150cm, the soil bulk density is between 1.26 and 1.67g/cm3, total porosity is between 30.89% and 46.78%, non-capillary porosity is between 8.36% and 17.32%, soil organic matter is between 0.93 and 3.20g/kg, nitrogen content is between 0.02% and 0.04%, phosphorus content is between 0.26 and 1.14g/kg, potassium content is between 81.08 and 263.53μg/g. There are 66 species of higher plant in the watershed, 11 species is the dominant plant species, vegetation types can be divided into forest, shrub and grass.Vegetation coverage is main middle coverage, the proportion is 45.03% of the total area. Forest and arable land is the main land use, accounting for 58.86%, 20.87%.2. The situation characteristics of soil erosion and its impact factorare is grasped.The area of soil erosion in wastershed is 432.20hm2, accounting for 47.91% of total land area. The watershed is water-eroded in the soil erosion primarily, mild erosion and moderate erosion are is the main soil erosion intensity, intense and extremely strong erosion are in Local area. The spatial distribution of soil erosion shows some regularity, slight erosion mainly in the junction of plains and hilly mountain slope area; moderate erosion mainly in the north and south basin slope; strong and very strong erosion mainly in the higher elevations.Soil erosion is close to the land use, slope and vegetation cover.In circumstances similar slope factors, Shelter is better than shrub land and grassland, the refurbishment of the drought better than the irrigated terraces, timber and other land use types; under the influence of variety offactors,15-25 slope rating region is the largest area of soil erosion. For vegetation cover, the intensity of soil erosion will reduce with the vegetation cover increases.3. The land suitability of watershed is evaluated. The land of watershed is mainly medium appropriate level land and barely suitable level land, the area are 397.34hm2 and 282.95hm2, mainly distributed in shelter, and it have a small amount of highly appropriate level land(70.77hm2), mostly in irrigated areas, not suitable level land is the least, the area is 55.34hm2, mainly in the barren lands. Through soil suitability analysis, influenced by soil erosion the most is the middle class and the very strong level of land erosion in marginally suitable land area. And we should pay attention to soil erosion control work of these areas.4. The three-dimensional simulation of small watershed has been come ture. In the current study of soil Erosion monitoring and evaluation of land suitability, often use thematic maps, but lack of three-dimensional spatial.Use the digital elevation model, aerial photographs, soil erosion and land suitability rank correlation as the data source layer, does the three-dimensional simulation for the wateshed, and more intuitive display of characteristics about the small watershed topography, soil erosion and land suitability.After the survey of watershed nvironmental factors, soil erosion and land suitability, and analyzes the problems of watershed, propose to adjust land use structure, combined with climate and terrain conditions, increased vegetation coverage of shrub land and grassland, appropriate increase landscape ornamental plant species, rich color degrees of the whole watershed, repair the watershed Gufang and low standards of terraces, change part of the terraced slope, and further optimize the land surface configuration.
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