Spatiotemporal Variation Of Soil Erosion In Red River Basin,China

The land use of Chinese part of Red River Basin is complex. The wide farmland area combined with the concentrated rainfall, which result in the serious soil erosion. The soil erosion threats to the grain production as well as the river health, food security and water and electricity energy development to the lower Red River countries. This study discussed the spatiotemporal distribution pattern of soil erosion using the precipitation, soil data, DEM (Digital Elevation Model) data, remote sensing image, land use data and so on of Red River Basin and based on "3S" technology, mathematical statistics and CSLE. And then describe and explain pattern-process relations in the view of the response that soil erosion to the land use landscape pattern changes. The results can provide a scientific reference for land use planning and soil and water conservation.The main research findings are as follows:(1) The soil erosion area is 39951.87km2, the averaged erosion modulus is about 18.411t·ha-1·a-1, and the gross erosion is 13634.81×104t in 2000 period of Red River Basin. The soil erosion area is 32569.70km2, the averaged erosion modulus is about 18.68t·ha-1·a-1, and the gross erosion is 13827.00×104t in 2010 period. The erosion area ratio of the moderate and under moderate soil erosion is as high as 90%. However, the contribution of basin erosion of the severe and more than severe erosion which account for less than 10% erosion area is as high as 57.19% to 64.99%.(2) On the elevation gradient, soil erosion intensity showed an increasing trend at first and after then decreased with the increase of altitude. The main regions where erosion occurred and the core area needed to be managed concentrated on 1000 to 2000 meters. The soil erosion intensity on the regions above 1500 meters decreased, but it increased below the 1500 meters. The soil erosion extended to low altitude area.(3) On the slope areas, the spatiotemporal distribution character of soil erosion showed that the soil erosion prevention should focused on the 15° to 35° slope area. The soil erosion area reduced at all slope regions except less than 5°area. Soil and water management work has achieved initial results. But due to a slight increase of erosion modulus, the erosion is still increased.(4) On the soil type areas, red soil and latosolic red soil regions are the key area of soil and water conservation. The erosion area and erosion amount are all account for 20 percent of the basin in purple soils. Since the purple soils are mainly distributed in the northern, northeastern basin and the upstream rivers. Therefore, the soil and water conservation in these regions is rather important.(5) On the land use patterns areas, the most serious soil erosion was in farmland, followed by grassland and forestland. During the soil and water conservation in the basin, it is essential to enhance dry land (mountain) and high coverage grassland management and keep slope farmland distributed on 15° to 35° and 1000 to 2000 meters from serious erosion. At the same time, it is crucial to control the erosion amount of high altitude farmland. Futhermore, it is necessary to deal with the relationship between high coverage grassland and other grassland, forest land and farmland:making the land use transfer to be beneficial to soil and water conservation; creating conditions to transfer shrubland to typical forest land in the areas that suitable the forests expansion; reducing the area of shrubland appropriately; prohibiting the cultivation of shrubland in the meantime.(6) The results of RDA indicated that combination of the eight explanatory variables including Number of Patches index of dry land (hilly area), Total Area Index of high coverage grassland, Connectance Index of middle coverage grassland, Perimeter-Area Fractal Dimension Index of dry land (mountain), Total Area Index of shrubland, Total Area Index of forest land and SHAPE-AM Index of forest land can well explain the change of soil erosion. To control soil erosion effectively, it must be take some targeted measures:firstly, adjust the layout of mountainous farmland appropriately, regular farmland to avoid the excessive fragmentation of cultivated land, return farmland to forest and grass in a timely manner to the small piece of cultivated land with lower productivity. Secondly, make sure the concentrated distribution to the high coverage grassland, take measures to return the unsuitable cultivated land to forest and grass land, do not weaken the grass land's overall function of keeping soil and water to pursuit the short-term benefits. Finally, take measures to reduce the area of the single shrub patches appropriately.