Research Of Ecological Security In Shule River Basin Based On Land Use And Landscape Pattern

Shule River, located in western part of Gansu province, is one of the three large inland rivers in Hexi Corridor and has the characteristics of typical inland arid area; its ecological environment is superbly vulnerable. Along with the implementation of western development strategy, China has paid more and more attention to protection and construction of western ecological environment. The ecological security pattern of Shule River Basin is extremely important. Landscape ecology, remote sensing and geographic information technology provide methods for the analysis of landscape pattern and ecological security of the basin. Based on the collected hydrological and geological data, the social economic data, remote sensing images as well as the land use data of Shule River Basin, the principles and methods of landscape ecology were applied; then, the appropriate landscape pattern indexes were selected; finally, the landscape pattern characteristics and the land use dynamic change of the river basin from 1980 to 2010 were analyzed in the thesis. In addition, the suitable ecological security evaluation model for the basin were constructed on the basis of landscape pattern indexes; the risk areas were divided so as to evaluate the ecological security of the basin; space-temporal evolution of its ecological security degree was analyzed and the spatial correlation was studied. Besides, the minimum cumulative resistance(MCR) model were used to build river basin ecological security pattern taking nature reserves, waters, forest land as the “source”, and ecological security level, elevation and slope as resistance factor to generate resistance surface. The potential corridors and nodes were identified and the optimized ecological security network was established; some suggestions and countermeasures were put forward for the sustainable development of the river basin. The main conclusions of the thesis are as follows:(1) Grassland, desert and unused land are the main landscape types of Shule River Basin. The area of arable land and urban industrial and mining land is ever-growing during the research time, and gradually presents aggregated distribution; the area of the transformation between the two accounts a bigger proportion; Quantity change degree is the most dramatic. Sandy land is always the basin landscape with the most complex shape. The distribution of wetlands is more and more fragmentized; the degree of change of water area and wetlands are relatively strong. The mutual transformation among other unused land, desert, saline-alkali land and the grass is the main part of the basin land use change.During the study period, the land use conversion speed of basin reduces gradually, the number of landscape patches decreases obviously; landscape diversity increases; the fragmentation trend is obvious. The change of landscape shape before 2000 tended to complicate and then tends to simplify.The dynamic degree of land use and landscape pattern in Shule River Basin from 1980 to 1995 is far more than that from 1995 to 2010.(2) The ecological security level in south of Shule River Basin is higher than that in the north; the low safety areas are mainly distributed in the northern river basin; while the higher safety areas are distributed in the southern mountain area and in the middle and lower reaches of the river alluvial plain; high safety areas are distributed in the southeastern Qilian Mountain area, the junction of Subei County and Yumen City. From 1980 to 1995, the areas of Shule River Basin with ecological security level change are mainly located in the southwest and the east; the area of the places with the ecological security level change from 1995 to 2010 is less than that from 1980 to 1995. Lower safety level area is the largest regional area in the study area from the start to finish, followed by the low safety level area while higher safety and high safety level areas account quite small proportions in the study area, with the sum of the two less than 10%. In general, its ecological security level has been improved in 30 years.(3) There is a certain accumulation effect in landscape ecological security index in space of Shule River Basin. If the areas have high ecological security value, the value of the surrounding area is high, and vice versa. At the same time, on the local space, the characteristics of the “homogenous agglomeration and heterogeneous separation” are obvious. From 1980 to 2010, Moran’s I Index showed a depressed trend; the degree of spatial autocorrelation weakened; space homoplasy gradually reduced. From 1980 to 2010, its spatial distribution of ecological security indexes was mainly high-high(H-H) aggregation and low-low(L-L) aggregation types, while high-low(H-L) aggregation and low- high(L-H) aggregation were scattered in distribution.(4) The optimized ecological network combines ecological source region, potential corridors and nodes and other landscape components, and makes it become a whole with the mutually nested points, lines and surfaces. Compared with the status quo of river basin ecological security pattern, the potential ecological security network makes full use of the existing river system, gets through the corridors, avoids urban industrial and mining land and transportation lines, connects the ecological source regions such as nature reserve through corridors and radiation roads, and sets up key points in the ecological fragile district as the “pedals” of species dispersal.