| The project of converting farmland to forest (also known as Grain for Green Project, GGP) is one of the six key forestry ecological programs of China. The GGP quickened the pace of soil erosion and land desertification control, increased the income of farmers, accelerated the adjustment of industrial structure and promoted the development of environment quality to good direction. The GGP as a complex project was related to different regional ecological and economic and social sustainable development. Form begin pilot of 1999 to full implementation of 2002, the GGP has now entered a phase of the later stage (2011-2020), the problem that how to effectively evaluation the ecology benefits of the GGP was not only needed to research and solve at present, but also concerned by national and researchers. A case study on the Hongya County in hilly region in Sichuan Basin, based on the remote sensing imagines of TM, and in combining with the 3S technologies and mathematical statistics methods, this paper analyzed the changes of the land use/ cover and ecology benefits before GGP (1994-1999) and after GGP (1999-2007), and explored the impact of the GGP on different regional ecology benefits.(1) Based on the 1994,1999,2007 multi-source remote sensing imagines of TM, the land use/cover types was built by using supervised classification, the overall classification accuracy of 1994,1999,2007 was 87.35%,82.61%,89.32%, the kapper index of 1994,1999,2007 was 0.8609,0.8087,0.8850, the results were stable and reliable.(2) Forest and farm land were the major types of Hongya County. The changes of land use/cover types were not obvious between 1994 and1999, but significant changes were observed during the period of 1999 to 2007, a large number of farm land converted to forest, the total area of farm land had decreased 2.39 X 104hm2, The major decreased of farm land was cropland; the total area of forest had increased 2.25×104hm2, The major increased of forest was broad-leaved forest.(3) According to the principle and availability of indicators selection, and in combining with the specialists inquired method, this paper choose plant cover, water supply, soil erosion modulus and biodiversity as indicators for ecology benefit of GGP in Hongya County.(4) The paper analyzed the dynamic of the evaluation indicators of ecology benefit, based on the 3S technology and field investigation, and in combining with the relative dates. Before GGP construction (1994-1999), the plant cover had decreased in Hongya County, the area of high plant cover had decreased 1.74×105hm2; water conservation had decreased 0.07 X 107m3; the soil erosion intensifies, The each soil erosion grade was increased except slightly erosion, the area of slightly erosion had decreased 0.31×105 hm2, the vegetation evenness index had increased 0.007. After GGP construction (1994-1999), the plant cover had increased in Hongya County, the area of high plant cover had increased 0.98×105hm2, the area of low plant cover had decreased 0.65×105hm2; water conservation had increased 1.37×107m3; the soil erosion had decreased, The each soil erosion grade was decreased except slightly erosion, the area of slightly erosion had increased 0.40 X 105 hm2, the vegetation evenness index had increased 0.057.(5) The model of ecology benefit was established by using data standardization method and analytic hierarchy process (AHP), and analyzed the dynamic of the ecology benefit in Hongya County during the GGP. The ecology benefit of Hongya County was south-west high and north-east low, the ecology benefit was overall in the middle level. Before GGP construction (1994-1999), the ecology benefit had decreased, the area of relatively poor level had increased 1653.21hm2; the area of poor and general level had decreased 1250.01 hm2 and 333.27 hm2; the fairly good level decreased slightly. After GGP construction (1994-1999), the ecology benefit had increased, the area of fairly good and good level had increased 17526.33 hm2 and 8495.19 hm2, the poor and relatively poor level had decreased 6973.47 hm2 and 19155.69 hm2; the highest increased of area was general level, the highest decreased of area was relatively poor level, and the fairly good level changed most, its annual variance ratio was 83.5%. |
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