Study On The Relationshop Between Different Land Use Types And Soil And Water Conservation Benefits In Purple Soil Area

Soil and water erosion in hilly areas of the middle Sichuan Basin is extraordinary seriously in China. This area has an enormous population, but the field is not enough. It is enrolled in the prevention and cure project in upper reaches of Yangtze River. The research is about the relationship between different land use types and soil and water conservation benefits of forty small farming watersheds in purple area. The major conclusion is as the following.(1)After the management of the forty small farming watersheds, soil erosion modulus of different land use types from big to small is wasted land (12322.59t/km~2·a), slope land(2396.74t/km~2·a), wood land(1478.35t/km~2·a), other forest land(1434.20t/km~2·a), other land(839.19t/km~2·a) and flat tilled land(-633.35t/km~2·a). The management for soil and water conservation should be carried out on slope land and wasted land first.(2)After the management of the forty small farming watersheds, the number of retained runoff per unit area by rice paddies and slope land is 437.5 thousand m3/km~2 and negative 280 thousand m3/km~2;the number of retained runoff per unit area by bush land, small wood land and grass land is 1,055.3 thousand m3/km~2,290.6 thousand m3/km~2 and 2,191.5 thousand m3/km~2。The average retained runoff ratio of different land use types from big to small is rice paddies(171.34%), small wood land(62.95%), bush land(23.22%), grass land(2.00%) and slope land(-75.88%). Rice paddies dose actively in retaining runoff but slope land dose negatively.(3)After the management of the forty small farming watersheds, the number of intercepted soil per unit area by slope land, wood land and small wood land is 1.9 thousand t/km~2, 2.0 thousand t/km~2 and 3.0 thousand t/km~2.In the different kinds of basic farmland, the sand content in slope land per unit area is biggest and it means that the soil erosion on slope land is very serious.(4)The overriding influence factor about the area of changing slope to the ladder is the management area of water and soil erosion and the minor influence factor is the area of all watershed, the area of abrupt slope and the area of fruit-bearing forest. The overriding influence factor about the area of soil and water conservation forest is the management area of water and soil erosion and the minor influence factor is the area of water and soil erosion, the area of terrace, the area of slope land, the area of wood land and the area of small wood land. The overriding influence factor about the area of fruit-bearing forest is the management area of water and soil erosion, the area of fruit-bearing forest and the area of wood land. The overriding influence factor about the area of prohibit measure is the management area of water and soil erosion and the minor influence factor is the area of water and soil erosion, the area of slope land, the area of wood land and the area of fruit-bearing forest. The overriding influence factor about the area of soil conservation farming measure is the management area of water and soil erosion and the minor influence factor is the area of all watershed, the area of water and soil erosion, the area of other land, the area of terrace, the area of slope land and the area of wood land.