Landscape Pattern Changes And Regional Ecological Security Assessment With Water Resource Allocation In Arid Oasis Area,Northwestern China

Ejin Oasis is located in the lower reaches of the Heihe River Basin, which is the northwest China’s second largest endorheic drainage. It is one of the important parts of the Ejin desert region, and also a crucial defensing ecological line in Northwest China. Taking the Ejin natural oasis landscape as the research object and using the remote sensing images of1987,2001and2009as the data sources especially focusing on watershed landscape, I apply the principle of landscape ecology and ecological evaluation method comprehensively in support of the3S technology. This thesis analyzes the dynamic change and the spatial distribution characteristics of the Ejina natural oasis landscape pattern before and after its water allocation. Then I build the ecological security assessment index system and evaluation criteria of the Ejin natural oasis landscape discussing the ecological security problems of the study area. Thus, this thesis provides a theoretical basis and scientific guidance for the maintenance of regional ecological security. The main research results show that:1) Water is the most important environmental factor to determine the vegetation development and evolution of the arid areas, and thus the vegetation in this region takes on obvious spatial distribution characteristics. The vegetation coverage is greater in the areas where are near to the riverway. These areas have more shrubs and forest vegetations, larger amplitude of the interannual variation and more sensitive response to water change; Whereas in areas far away from the river, the vegetations are mainly in the state of the desertification, the landscape patches are more broken, and the response to the water re-allotion is lag.2) The Ejin Oasis landscape takes on an obvious time evolution characteristics before and after the water allocation. From1987to2001, this region experienced the more serious desertification, vegetation reduction and ecological deterioration. After2001, the vegetation recovered obviously, and with the enlargement of the water area, the oasis enjoyed a positive evolution and the increasing vegetation coverage. 3) There are totally25indicators from the four aspects of landscape changes, water safety, environmental safety and socio-economic safety, which construct the ecological security assessment index system of the study area’s landscape. Using fuzzy comprehensive evaluation method, this thesis gets the ecological security index LSI of the Ejina natural oasis landscape is0.6556, which is generally on the side level. After nearly10years of water allocation, the ecological safety of the Ejin natural oasis landscape is gradually transferring from the deterioration to the good state. However, in order to achieve a more secure level, it still needs a much more scientific ecological planning.