| The ecological environment is the cradle of human survival and its development, and it is also the foundation of economic development and social progress. The ecological environment has been seriously affected and destroyed along with the intensification of human activities. In order to this, ecological security has become an important problem which the human being faced with to keep study. Great changes have taken place in recent30years in the ecosystem of Yanqi basin, and the ecological service functions have been changed also, the changes of ecological service function also influenced the human life and social development. In this paper, the change of various ecosystem service function value of different land use/cover is analysed, and temporal and spatial variations of the ecological system service value and the ecological footprint in the research area is analysed, by introducing the ecosystem service function theory to the ecological footprint model and referencing the calculation methods which the other researchers improved the main parameters in the model recently. Then, the ecological security in research area is evaluated, the ecological security situation in the region in the next20years is forecasted, using the ecological pressure index. The research results have certain reference function to the maintenance of oasis ecological security in Yanqi basin. The main conclusions are as follows:(1) The remote sensing interpretation of land utilization type is established and the land use data of Yanqi basin in four period, such as in1990,2000,2005and2011are got, using the information sources of remote sensing, combining with other thematic information and field investigation related. Analyses the land use/cover change in Yanqi basin between1985-2011, in combination with the land use/cover data in Yanqi basin in1985and1996that provided by the Data Center of the China Western Ecological and Environmental Science. The results showed that:obvious changes have taken place in the various types of land use/cover in Yanqi basin between1985-2011, among them the wetland, farmland and construction land increased, the area of unutilized land, salinized land, grassland and forestland decreased, the area of water and sandy land changed little. During the study period, the transfer of grassland to farmland is the most, mainly because of the occupation of grassland by the population increase and the rapid economic development.(2) The quantitative evaluation methods of ecosystem services value is improved, the comprehensive assessment model of the ecosystem services value in Yanqi basin is established, according to the characteristics of the natural environment in the study area. On the basis of this model, the services value of different ecosystem types in different periods and the total value of ecosystem services were calculated and analysis its changes in the study area, as well as the unit price of different ecosystem services project and its spatial migration changes. Results showed that:between1985-2011, the total value of ecological services in Yanqi basin increased from7milliard511million600thousand to1billion225million700thousand that it increased first and then decreased. Between1985-2011, the net increase is2milliard714million100thousand, average annual increase is104million389thousand. Among them, the total value of ecological services increased during the different periods of1985-1990,1990-1996and1996-2000, it increased3milliard71million500thousand in the15years, and the average annual increase is204million767thousand. During the two periods of2000-2005and2005-2011, the total value of ecological services in the study area decreased, the total loss in11years is357million400thousand, the average annual loss is32million491thousand. Because the increase of the ecosystem services value during the first three periods is larger than the loss of the ecosystem services value during the latter two periods, the total value of ecosystem services in the study area keep on the increasing state, and the ecosystem services function is increasing continually.(3) The volume of the all kinds of ecosystem services value in the study area related to the area change of the land of each ecosystem type. During the study period, the contribution of ecological services value of water area to the total value of ecosystem services in the study area is the largest (above43.8%) among the nine ecosystems, secondly is the wetland (above 16.1%). Although, the area of this two account fewer than27%of the total area of land use in the study area, but the ecological services value provided by them accounts above59.9%of the total value of ecosystem services in the study area. The area of unutilized land and farmland accounts above49%of the total area of land use in the study area, but the ecological services value provided by them accounts under21%of the total value of ecosystem services in the study area.(4) In this paper, the ecological footprint (demand) and the ecological capacity (supply) between1985-2011in Yanqi basin is calculated using the ecological footprint model which is improved on the basis of the theory of ecosystem services function. Between1985-2011, the average ecological footprint (demand) increased gradually in Yanqi basin, it increased from0.5587hm2/person in1985to4.0892hm2/person in2011, the average annual increase is6.91%. The sum of the ecological footprint of the average fossil fuel land and the ecological footprint of the average grassland, as the main components of the average ecological footprint in Yanqi basin accounts70%of the average ecological footprint, and the proportion increases more.(5) The ecological footprint in the counties of Yanqi basin has large regional differences. The volume order of the ecological footprint is:Hejing county>Yanqi county>Heshuo county>Bohu county, the change of the average ecological footprint in Hejing county is between0.5640-5.0529hm2/person. It is same with it that the consumption of resources is large and the living standards are higher than the other counties in the economic center of which the Hejing county and the Yanqi county is the study area. The ecological footprint of the types of land in counties of Yanqi basin have large regional differences, among them the ecological footprint of the types of land is the largest in Hejing county, it is the smallest in Bohu county.(6) The average ecological capacity has decreased a small amplitude between1985-2011in Yanqi basin. Composing of the average ecological capacity in Yanqi basin is uneven, the main components ara the ecological capacity of water area, the ecological capacity of grassland and the ecological capacity of farmland, the three account more than97%of the total ecological capacity in this year. The main reason is the land resources in the scope of the study area. The average ecological capacity decreased in small wave in the counties of Yanqi basin that it is same with the ecological capacity in Yanqi basin. From the point of the volume of the average ecological capacity, the average ecological capacity in Bohu County is higher than the other three counties. Secondly is the Yanqi County. The types of ecological capacity in the counties of Yanqi basin have regional differences. Except of the forestland and unutilized land, among the average ecological capacity of other types of land, Hejing County is the lowest, secondly is the Yanqi County.(7) The ecological tension index is increasing between1985-2011,it increased from-0.8559in1985to0.4622in2011, among this the increase speed between2005-2011is the most. In Yanqi basin, characterization of security condition in1985-1996is very safe, characterization of security condition in2011is a little not safe. The change of ecological security index has obvious regional differences in the counties of Yanqi basin. Seen from the space, the volume order of ecological pressure index is:Hejing county>Heshuo county>Yanqi county>Bohu county. Bohu County is the highest; the ecological security level in Hejing County is the lowest. The ecological pressure index in Hejing County is higher than the average level in Yanqi basin, the rest are lower than the average level in Yanqi basin, it shows that Hejing County is the place that security level is the lowest. |
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