Dynamic Study On Landscape Patterns After Conversion Of Farmland To Forests In Hongya Based On 3S Technology

The Conversion of Farmland to Forests Project (CFF) is a major strategic decision with focus on the long term sustainable development of national social economy in china, one of the six great forestry ecological projects in China, it is a fundamental measure to control water and soil erosion, restore soil degradation, improve ecological environment, it plays important role in keeping ecological balance, developing low carbon economy and maintaining regional ecological security. Stage achievements had been gotten since 1999 the implement of the project, but the landscape pattern and changes in ecological process need for long-term research and scientific assessment after the CFF, it is necessary to monitor the project implementation status and benefit evaluation, studying the changes of landscape pattern is important to evaluate the CFF reasonably.Based on RS,GIS and GPS technology, taked Hongya County Sichuan Province as example, the remote sensing image of Landsat TM in 1994(before CFF),Landsat TM in 2004(interim CFF),Landsat TM in 2007(after CFF) were used as information source, supplemented by topographic maps and other raster data, used landscape ecology theory and methods, studied the changes of landscape patterns before and after CFF, analyzed the impact of great forestry ecological projects to the changes of landscape pattern, provided reference about regional ecological environment protection, eco-tourism development and related eco-industries. The results indicate that:1. Used original band data of Land sat TM image, created new band NDVI, and excluded the original image the 6th band, re-synthesized new 7 band image data. Based on the new image, the resultant classification of landscape was obtained by using the methods of supervised classification and manual interpretation, improved the classification accuracy, the overall accuracy of 3 classification maps arrived at 87.35%,86.56%,89.32% respectively, the classification results were reasonable and they could be used in dynamic analysis of landscape pattern.2. With the support of ArcGIS, the analysis of area changes and conversion matrix in different landscape types showed that:The farmland area had reduced, the forestland area showed an increased trend, forest coverage before CFF, interim CFF and after CFF was 56.88%,66.52% and 68.42% respectively.1994-2004 the conversion of landscape types were much higher than 2004-2007, the conversion of landscape types trended to stabilization. According to the area changes and area conversion between farmland and forestland, the implement of the project caused farmland area decreased and mainly transferred into forestland, the CFF project achieved some success.3. The slope, aspect and elevation were extracted and slice level from DEM by ArcGIS, study on topographic differences of various landscapes by using ArcGIS of Spatial Analysis Module showed that:The distribution proportion of landscape types in the different topography level existed differences. Distribution of farmland was prone to low elevation during 1994-2007, the distribution proportion of farmland had declined significantly in 1000-1500m, while the distribution proportion of coniferous forest and broadleaf forest had increased maximum in this elevation level. The distribution proportion of farmland had decreased under steep slope, but coniferous forest and shrubbery had increased. Farmland trended to non-aspect, coniferous forest, broadleaf forest trended to shady slope, semi-shady slope, and shrubbery trended to the sunny slope, the trend of bamboo liked as farmland.4. Dynamic analysis of landscape pattern indexes under patch type level and landscape level showed that:The fragmentation degree of dry land and paddy field had increased, the patch shape became simple the spatial connectivity had decreased. The framentation degree of Coniferous forest, broadleaf forest and shrubbery had increased, the patch shape became complex, and the spatial connectivity had increased, but the framentation degree of bamboo forest had decreased, the patch shape became simple, and the spatial connectivity had significantly increased. Landscape was prone to diversification and homogenization, the framentation degree had increased, it indicated that the ecosystem became more complicated, ecological function became better after CFF project in Hongya County.5. Driving analysis of landscape changes showed that:both natural factors and human activity had some impact on landscape changes, but the human activity was the decisive factors among 13 years in Hongya County. The area of returned farmland was 14599.85 hm2 in Hongya County until 2007, account for 61.02% of farmland reduction area, we could see that policy dominated landscape changes in Hongya County from the changes of farmland and forestland after the implement of the CFF project.