| Ejina Oasis is located in the lower reaches of Heihe River Basin in the arid inland regions, the northwestern of China. It is a typical representative of oasis in the arid area, and also a crucial defensing ecological line in the northwestern of China. Since the 1960s, as the overusing of water in the middle reaches of Heihe River Basin, the amount of water falling to the lower reaches decreased drastically which lead to a series of ecological and environmental problems. In order to improve the ecological environment, the project of water allocation was launched in 2001.Taking Ejina Oasis landscape as the study object, and using the remote sensing images of 2001 and 2014 as data sources, this paper interpreted remote sensing images in use of remote sensing processing software, ENVI 4.7, to obtain information of landscape types. Based on the landscape type maps this paper analyzed the landscape changes of Ejina Oasis with landscape dynamic degree and the transfer matrix of landscape area; then carbon stock services, sand-fixing services and habitat services were evaluated and mapped with InVEST model and quantitative indicators,and then the spatio-temporal changes of landscape services from 2001 to 2014, hoping to expand the view of the landscape restoration of Ejina Oasis and provide scientific basis for the rational use of resources of the arid area. The main findings are as follows,(1)The main landscape types in Ejina Oasis are riparian vegetation, desert vegetation, water, urban and artificial construction and other landscape(including Gobi, Sand, Saline and so on).By analyzing landscape changes of the study area, we found that the area of Riparian vegetation, Desert vegetation, Water, Urban and artificial construction all increased to different extent, and the area of Riparian vegetation increased the most while Water fastest. On the other hand, only Other landscape decreased drastically. By analyzing the mutual transformation between the landscape types of the study area from 2001 to 2014, we found that, the transformation of riparian vegetation and desert vegetation mostly occurred between each other. Desert vegetation and Other landscape contributed larger to the transformation of Water. In addition, Other landscape (including Gobi, Sand and so on) contributed relatively large to the transformation of the other four landscape type.(2) Carbon stocks of the Oasis landscape and the amount of sand-fixing of the vegetation all increased by 1.022×106t and 1.239×106t from 2001 to 2014. And all the four vegetation landscape types’carbon stocks and the amount of sand-fixing increased to different degree, especially riparian vegetation increased the most. In addition, high value region of carbon stocks and the amount of sand-fixing in the area was mainly distributed in the core area of oasis, and high value region in 2014 was larger than that in 2001. Carbon stocks and the amount of sand-fixing were obviously effected by the river corridor, that is to say, the farther it was away from the river, the less the amount of carbon stocks and sand-fixing. At last, the amount of carbon stocks and sand-fixing in the east bank of the river was greater than the west bank.(3) Similar to the above two kinds of landscape services, high value of habitat service was mainly distributed in the core area of oasis and rendering gradient decreasing from the center to the periphery. On the other hand, the distribution of high value of habitat services was larger in 2014 than 2001.(4) A comprehensive evaluation of the three kinds of landscape service indicated that, the supply hotspot was mainly distributed in the core of the Oasis, and the distribution of high value integrated services was larger in 2014 than 2001. And also, the supply mean value of the four kinds of vegetation landscape were different, but overall, riparian vegetation contributed more to the three landscape services, while desert vegetation relatively less. |
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