GIS-based Land Eco-security Evaluation In The Three-Gorges Reservoir Area

Ecological security is an important component of national security, land eco-security is the basis of land sustainable development, but also the basis of socio-economic sustainable development. With the increasing environmental pollution and serious ecological damage, land eco-security has become the forefront research tasks and important area of ecology,geography,resources and environmental science current. Research on the backward economic developmentment,eco-fragile and sensitive area of the Three Gorges reservoir area is particularly important to the land restoration and improvement of ecological environmen.This paper take the area along the Yangtze River of Fengdu County in the Three Gorges Reservoir as an example, combined with the Three Gorges follow-up Project's land ecological functions planning of Fengdu County, using GIS this paper studied land use change,topography,geological disasters,vegetation cover and landscape patterns, on the basis,this paper analyzed the comprehensive evaluation of the land eco-security of research area. Lastly,combined of evaluation results and land use characteristics,divided study area into different ecological functional zones, proposed land-use optimization models and land protection of ecological restoration measures. Main contents and conclusions are summarized as follows:(1) In the period 1996-2005, land use change showed that cultivated land,,forest land,badlands are reduce, plantation, construction land increased are.increase,and plantation increase most Because of the economic center has shifted from the north shore to the south bank of the Yangtze River, causing the south shore's land use change faster than the north. Ecological buffer zone's main land-use type is cultivated land, with low forest cover, it's land ecosystem appear degradation trends, ecological environment is extremely fragile.(2) The topography and land eco-security is closely related,urban land are mainly distributed in the lower elevations around the Yangtze River reservoir banks, paddy fields, plantation, dry land, also concentrated in low altitude areas, which reflects the human interfere mainly embodied in the ecological buffer zone, while the higher elevation areas are mainly woodland, land ecological status is relatively good. Although with the slope's increasing, gravity caused soil erosion increased,but accompanied by the increasing in slope,the dominant position of woodland is gradually increase, and woodland reduce the ecological risks of land. However, the study area>25°of slope cultivated land accounts for the total area of cultivated land's 9.21%, between 15°-25°cultivated land also accounts for a considerable proportion, it's soil erosion should not be overlooked.(3) Geological disasters have seriously affected the pattern of regional land eco-security, the study showed that lithology, topography, vegetation cover and human economic activity are closely related to the development of geological disasters. According to layer overlay statistics, geological disasters mainly concentrated along the Yangtze river,long river vally.and surrounding the roads.where the town mainly distributed in, and they are a serious threat to the residents personal and property safety.(4) The vegetation cover are mainly distributed in 20%-40% in study area, and from the overall level, vegetation coverage showing a downward trend. Using landscape indices software Fragstats 3.3,the study area landscape pattern analysis shows that cultivated land have greater dominance in the north shore of the Yangtze, and woodland showed greater dominance in the south shore. From Landscape features perspective, the south shore's landscape fragmentation is less than the north shore, man-made landscape types concentrate distributed in the ecological buffer zone, and its diversity index, fragmentation index were higher than the entire area along the Yangtze River.(5) Reference to P-S-R framework, this paper proposed land eco-security index system of study area,using AHP and GIS achieved the land eco-security evaluation with grid unit. Studies showed that land eco-security status mainly composed of safer status and warning state in the study area, severe and moderate warning area mainly distributed in the ecological buffer area. By the land eco-security analysis, cleared the formation of the regional land eco-security pattern.(6) Based on the land eco-security assessment results, the research divided the study area into three ecological function areas:riverside urban ecological restoration areas, hills agro-ecological zones and low mountains forest-protected areas. Combinated with the characteristics of regional resources and existing ecological problems, this paper proposed different land use patterns and ecological risk prevention strategies, In order to provide a reference to the sustainable development of land.