A Study On Influences Of Land Use Pattern Changing On Soil And Water Loss In Small Watershed Of Loess Plateau Gully Region

Exploring the erosion rules, seeking the ways and methods to protect plateau and control soil and water loss, is an important task of soil and water conservation in Loess Plateau at present. This paper based on the Land Resource Science, Landscape Ecology Science, Soil and Water Conservation Science and combining with RS, GIS technologies, took the small watershed of Yangjiagou in Loess Plateau Gully Region as the main study area,and compared with Dongzhuanggou watershed, analysised the soil and water loss changing situation of Yangjiagou small watershed through "Standards for classification and gradation of soil erosion" issued by Ministry of Water Resources, to explore the impact of land use and landscape pattern change on soil and water loss, then promoted optimal allocation model of land use pattern, in order to provide theory for soil and water loss control in Loess Plateau. The results show that:(1) Since taking soil and water conservation measures in early fifties, the land use and landscape pattern in Yangjiagou watershed have a large change. The area of forest land was increased greatly and the area of unexploited land was lowered sharply. In addition, the area of grassland,garden land and communication land were increased in different degree. The area of cultivated land showed the changes of first increasing and then decreasing.The main changes of land use was unexploided land to forest land. In general, the land use pattern has changed into forests land and cultivated land in main from unexploided land and cultivated land in main.(2) The unexploeded land, cultivated land, forest land in Yangjiagou watershed were of larger landscape fragmentation, more complex shapes and developed more quickly. The communication land, garden land, grassland were relatively stable. In general, the landscape fragmentation, shape index, evenness and diversity in Yangjiagou watershed were all increased more and less. (3) The soil and water loss situation had improved significantly. The number of annual flow and the annual rainfall were reduced, the water storage was increased, the sediment yield was reduced, the soil bulk density was reduced and the soil porosity was increased. The area of slight, mild soil and water loss was increasing and the area of strength, extremely strong, severe soil and water loss were shringking.(4) The mainly souces of soil erosion were unexploited land and cultivated land. The landscape of unexploited land and cultivated land which had large contribution to soil erosion showed patch number increasing, average patch area decreasing and fractal dimension and shape index decreasing recently.(5) Although the soil and water loss had been effectively controlled in Yangjiagou watershed, we should strengthen soil and water loss control, adjust land use type and land use structure. A part of steep cultivated land should be converted into forests, the quality of forests should be improved, the further planting should be taken to improve the utilization of unexploited land.