| For a long time, because of so much attention paid on increasing food production and excess woodcutting in the Three Gorges reservoir area, resulting in the high proportion of steep sloping fields, low forest cover, severe soil erosion and ecosystem degradation significantly in this region. With the completion of the construction of the Three Gorges Project, the immigration prosperity and economic construction, the human's activity has non-stop to impact the land use and local Eco-Environment level. Owing to this, the paper uses the Caotang River basin in Fengjie County as an example, combining the theory and method of landscape ecology and restoration ecology, based on three remote sensing images of the Caotang River basin in 1990, 2000, 2007, analyses the changing character of landscape pattern by using 3S technology. Combined with other related materials, mastering the general situation of ecological systems on the basis of threat, respectively, from the sloping fields, soil erosion, and construction of Three Gorges Project to analyze the ecosystem threat characters of Caotang River basin, and finally for ecological restoration of Caotang River basin analysis.The main contents and conclusions of this paper are follows:(1) Because long-term effects of human activities and the change in the pattern of land use, the landscape pattern of Caotang River basin was greatly changed for the period 1990-2007. The main aspect was a significant reduction by 21.26 percentage points in cultivated land area, the area of garden, shrub-grassland and forestland was increased respectively by 3.51, 12.26 and 4.60 percentage points; advantage of the landscape shifted from farmland to shrub-grassland.(2) The period 1990 to 2007, the total sloping fields in Caotang River Basin fell from 16 356.40 hm2 to 8 038.62hm2. Among these, cultivated area which slope is steeper than 25°changed from 4 692.65 to 1 663.19 hm2, reduced by 8 percentage points.The area which slope is between 15°and 25°, 8°and 15°and less than 8°reduced respectively from 6 449.33 hm~2 to 3 221.88 hm~2, from 4 061.29 hm~2 to 2 341.65 hm~2 and from 1 153.13 hm~2 to 811.9 hm~2, but they were increased respectively by 0.65,4.30 and 3.05 percentage points. And cultivated area which steep slope gradient greater than 25°decreased 227.06 hm~2. In the past decade the green policies have some degree of success, but owe to the relatively backward economic development in the basin, less arable land and not in the area of slope greater than 25°regional farming is difficult to achieve, which is the main human factors of soil erosion. The average slope erosion modulus in Caotang River basin is 7 902 t/km2·a, erosion has reached the level of intensity, soil erosion situation is very grim, so the future of soil and water conservation task is more challenging.(3) The area of water-level-fluctuating zone is 346.23hm~2 in the Caotang River basin, accounting for 0.87% of the total area, of which construction land is 23.67hm~2, cultivated land is 251.28hm~2, garden is 60.52hm~2, shrub-grassland is 10.76hm~2. Drowned cultivated area is the largest, accounting for 53.25% area of flooded areas, and these lands are mostly fertile farmland. Reduction of arable land, migrants moving from lower place to higher, which are bound to increase the intensity of land development, further intensify the conflict between land and population in the basin.(4) In consideration of the key factors which caused degradation of sloping fields in Caotang River basin, the measures of ecological restoration and reconstruction were analyzed from three main aspects: ecological engineering, agricultural agronomic and biological measures.
|
PDF Full Text Request