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Lanzhou University (2016)

The Impact of The Oasis Development on Ecological Environment

张娟

Titre : The Impact of The Oasis Development on Ecological Environment

Auteur : 张娟

Grade : Master’s Theses 2016

Université : Lanzhou University

Résumé
The assessment of the impact of artificial oasis development in arid areas on ecosystem contributes to improving the understanding of the coordinated development of regional economy and then provides a theoretical basis to formulate sustainable ecology and economic development strategies. The development of basic space technologies, such as GPS, RS and GIS, brings great convenience for the assessment of ecosystem on the space scale. This study explores methods that are suitable for the evaluation of the ecological environment in arid areas relying on Geographical Situation Monitoring Project in Gansu Province— “Monitor Desertification in Hexi Corridor Oasis Dynamically”. With Guazhou-Dunhuang Basin as an example, we calculate the Ecological Environment Evaluation Index in 1986, 1995, 2005 and 2014, respectively, based on the Landsat TM/OLI remote sensing images. We then further analyze the impact of oasis exploitation on ecological environment with the process of the oasis development. Our contributions can be summarized as follows:1.We establish a simple ecological environment evaluation index that applicable to ecological environment in arid areas.By summarizing the relational literature about the assessment of ecological environment in arid areas, with the most basic ecological process-oasis and desertification as the focus, we select the Ecological Evaluation Index related to oasis : greenness and humidity ; the Ecological Evaluation Index related to desertification : desertification and salinity. Based on these four evaluation indexes, we apply distance function, and formulate ecological environment in arid areas. By comparing with the fieldwork data, we verify the applicability of the index.2.We analyze the greenness, wetness, desertification, and salinity in nearly three decades and explain the impact of oasis exploitation on vegetation, humidity, salinization, and desertification.Vegetation as a pointer factor ecological environment, which can significantly change reflects the changes of environment. The impact of oasis exploitation on vegetation includes three aspects,(a) oasis exploitation process replacing natural vegetation leads to a qualitative change of vegetation types about 520.12km2 ;(b) oasis agricultural production occupied ecological water leads to the degeneration of natural vegetation about 321.071km2 in Changma alluvial fan ;(c) the forestry and grass with the aim of oasis stability and sustainable development promotes effectively vegetation recovery in oasis periphery, and the vegetation moderate and obviously recovery areas in Dunhuang basin and Anxi basin are 246.902km2 and 234.258km2, respectively.During 1986-2015, oasis exploitation developed simultaneously with wetland degradation, salinization, and desertification. The areas of oasis development, desertification intensity increased, salinization intensity increased, and soil moisture decreased are 520.12km2, 971.052km2, 977.457km2, and 502km2, respectively. By analyzing spatial coupling relationship between oasis exploitation process and desertification, salinization, vegetable change, and humidity change, we show that the wetlands in all these regions were turning to dryness, the main reason of which is the occupation and exploitation of oasis agricultural exploitation for water resource and the decent of groundwater level. We also show that the dry zone in the wetland is the salinization increased zone. Moreover, because of oasis irrigation wash salt gathering in the surrounding artificial oasis, the level of salinization is increased, and thus, the main distribution area of the level of desertification increased is the area non-wetland soil became dried.3.We analyze the ecological environment situation in the research area, and we show the change of region of oasis exploitation.The ecological environment in the research area is poor integrally, and the difference of spatial distribution is significant. The continuous exploitation of the good ecology areas changes the overall ecological environment in these regions. The continuous expansion of oasis leads to the reducing of the area of good ecological natural landscape. The area of oasis exploitation on good ecological zones is 80% of the area of all exploitation area in research area nearly three decades. The natural landscape changing to artificial oasis leads all regions turning to high greenness.4.We analyze the temporal changing process of ecological environment in three sub-districts of research regions and show the impact of oasis exploitation on the natural landscape ecological environment outside the oasis.The ecological change tendency of Changma is degeneration-degeneration-mild recovery. Ecological changes in this region of three periods are mainly distributed in Bulong Ji- Suo Yangcheng area. The region has many springs overflowing and vegetation growing in good condition. The ecological change tendency of Anxi basin is degeneration-recovery-degeneration. Ecological changes in this region of three periods are mainly distributed in Westlake Village of Watershed downstream, The farther away from the West Lake farm artificial oasis, the more serious of ecological degradation. Ecological restoration is mainly because plantation of vegetation. The ecological change tendency of Dunhuang basin is significant degeneration-mild recovery-mild degeneration. Ecological restoration is mainly distributed in oasis around. Ecological degeneration is mainly distributed between oasis to Donghu lake or Nanhu lake, which was caused by the degeneration greenness and wetness

Mots clés : Guazhou-Dunhuang basin; oasis development; Ecological evaluation; Ecological and Environmental Effects;

Présentation (CNKI)

Page publiée le 18 juin 2017