| The Three Gorges Reservoir Area (TGRA) lies in the upper reach of Yangtze River Basin in central China. It has attracted worldwide attention because of the largest water conservation project in the world. This attention has not been only for its comprehensive social and economic benefits, but also for the potential security impacts on the natural environment and the potential geological disasters, as well as on the biological diversity imposed on the surrounding reservoir area. With population growth and human activities in the region since1980s, the land use/cover has changes rapidly because of excessive cultivation and over-felling. For example, the woodland area and the diversity of vegetation reduced quickly, which has resulted in forest fragmentation. Such changes have huge impacts on the eco-environment and biodiversity across the region. The objective of this study was to analyze the spatiotemporal pattern of land use and land cover (LUCC) in TGRA during1988-2007a, and therefore provide essential information for decision makers and planners to develop and implement land resources management and ecological environment protection in TGRA.Based on remote sensing, such as GPS and GIS technology;, combining mathematics model and space statisical analysis methods, the land use/land cover change, and land use structure optimization, landscape patern and its influencing factors, and ecosystem services were studied. The main results were listed as following:(1) The digitized stand maps from1988to2007were used to analyze change land use and land cover. The results showed that forest and farmland were the dominant land use and land cover types, which accounted for approximately90%of the study area. Significant increase in woodland and rapid decrease in farmland was observed in the study period. The farmland decreased by30.58%from31950.75km2in1988to22180.05km2in2007, while forest increased by26.91%from22312.08km2in1988to28317.02km2in2007. In the study period, there is a significant regional difference in LUCC and the change in the east was greater than in the southwest. The major patterns of land use change were the conversions of woodland to farmland and grassland, farmland to woodland and grassland, and grassland to woodland. The "’woodland to farmland" and the "woodland to grassland" changes indicated a high rate of deforestation. On the other hand, the "farmland to woodland" and "farmland to grassland" change indicated the land abandonment as well as the regeneration of woodland and grassland in this area. The conversion among farmland, woodland and grassland in this19a period was mainly due to the population expansion and the policy of conversion of farmland to woodland and grassland.(2) The multi-scale evolution of landscape pattern was analyzed. The results showed that in the study period, the spatial pattern of forest varied obviously. The increase in MPS was associated with a decrease in PD and a substantial increase in LPI, showing that the woodland became more clumped and gained land area from other classes of land. In the whole study period, there is a significant regional difference in landscape indices of forest and the changes in the east and middle was greater than in the southwest. Farmland area in the TGRA decreased rapidly. The NP increased from30223to31512between1988and2007. The PD increased from0.149per100ha to0.155per100ha, while the MPS decreased obviously from105.73to70.40ha. These results showed that the farmland became more fragmentation. The patch shapes grew simple and patches distribution concentrated, indicating that exploration and utilization intensity on farmland became much higher than before. The SHDI, SHEI gradually increased from1988to2007, showing that the heterogeneity degree of landscape increased and landscape type had a developing tendency towards complex direction.(3) By using the omprehensive information datebase of land landscape pattern and the regression model, factors influenced the landscape pattern were analyzed. The results show that the factors influencing the landscape type varied from land to land. For these major land use types, climatic and topography are the main factors influencing the landscape pattern.(4) Based on the data of land use/cover change in the three gorges area, the ecosystem service was quantitatively assessed. The results showed that:the ecosystem service value increased by144.04billion Yuan, and the ecological environment land use status were significantly improved from the year1988to2007. Forest land and farm land account for about90%of the ecosystem service value in the TGRA. Decrease in farm land area has significantly adverse impact, while the increase in area of forest land, grass land and water can positively influences on ecological environment. Comparing in different region, the ecosystem service value was much higher in the east part with complicated topography than that in the southwest part with low mountains and hills.(5) In order to lower the risk of soil erosion, the land use structure in TGRA was optimized. After optimization, the area of forest land increased5900Km2, and forest cover increased from10.3%to59.1%. The area of farmland and grassland decreased to33.8%and3.78%, respectively. The increased area of forest land comes from the decreased of farmland with steep slopes, the grassland with low attitudes or unused land with small slopes. Likewise, the soil erosion modulus and soil erosion amount decreased from2514.741km-2a-1,145.02×1061to2068.01t km-2a-1,119.31×106t, respectively. These results showed that soil erosion risk can be significantly decreased and the ecological environment can be substantially promoted after optimization of land use structure, which are benefit to the sustainable development of TGRA. |
