| Water resource is the main factor to influence the development of ecosystem in the inland river basins of the arid regions, northwest China. Especially ,with the exploitation in West China, the shortage of water resource and the contradiction of water resource allocation between economy and ecosystem have been severe constraints to the sustainable development of these regions, so it is essential to take these problems into account. In this paper, based on the principle of landscape ecology, using the Remoting Sense,GIS and a landscape structure analysis program, FRAGSTATS, taking Jiuquan oasis located in the middle reaches of Heihe River Basin as a example, the author studied the landscape pattern, change and ecological security. The conclusions are as follows:1. Make up the landscape type map of Jiuquan oasisFirstly ,we determined ecological classification of Jiuquan oasis landscape, then, build RS interpretation symbols of these types .On the basis of these data, using GIS (such as Arcview 3.2 and Arc/Info), we distinguished landscape elements and built spatial data base of these types. At last, the landscape type maps of Jiuquan oasis in 1986 and 2000 can be obtained.2. The analysis of landscape pattern and change of Jiuquan oasisAccording to the two landscape maps in 1986 and 2000, using Arcview 3.2 , its extended modules and FRAGSTSTS: spatial analysis program for quantifying landscape structure, we obtained the following results.(1) Oasis patches are heterogeneous mosaic of patches embedded in the matrix element Gobi-desert with absolute dominance.The characteristics of Gobi-desert are big patch size, high contagion. On the contrary, oasis types have relatively centralizedAbstractdistribution, big patch density and high diversity. These oasis types are largely distributed along rivers and channels, embodying the characteristic of hydrophilicity.(2) During the time from 1986 to 2000, the change varied with the patch type in Jiuquan oasis.But, as a whole, there is still a pattern of sharp contrast between oasis landscape and desert landscape . At administrative level, the denstity of landscape increased, the largest patch index decreased, the shape became more regularly, the diversity of landscape increased according to the SHDI and SHEI; at the same time, the landscape fragmentation degree ascended. As for the reason, the human activities have contributed to the landscape changes in Jiuquan oasis.(3) Study scale is very important in landscape ecology. We will draw different conclusions at different scales. At administrative level, the matrix is bare Gobi-desert, the landscape pattern embodied the characteristic of arid region, at oasis level, the Flat Glebe is the matrix.3. The analysis of ecological security of Jiuquan oasis(1) Threatened degree of desertification and salinization of jiuquan oasis. By using GIS, we studied the spatial neighboring characteristics between desert /salina and other oasis patch types in 1986 and 2000. Then, based on the foundation data, we calculated the threatened degree of desertification and salinization of jiuquan oasis. The results are as follows: the threatened degree of desertification increased, the threatened degree of salinization decreased , and the degree of desertification increase is stronger than the degree of salinization decrease.(2) The assessment of fitting oasis size and arable oasis size based on the actuality of water resource and the quantity of ecological water requirement. The result indicated that according to the present quantity of water resource in 1986, the area of oasis can increase 12608.07ha, but the area of flat glebe is bigger than arable oasis size; however, in 2000, the area of oasis is bigger than the fitting oasis size and the area of flat glebe is also bigger than arable oasis size. Ecological requirement can't be satisfied, so the measure of moving back flat glebe to woodland should be taken.(3) We selected indices to quantify the function and benefit of the Jiuquan agriculture ecosystem...
|
PDF Full Text Request