| As comprehensive and basic resources, land carrying all the biotic and abiotic on earth; while also providing material sources for human survival and development. However, with the level of technology advances, the human ability to extract resources from the land is growing, along with produce a series of environmental problems, for example land degradation, ecological deterioration, environmental pollution, soil erosion and so on, which make the sustainable use of land resources to produce a serious impact.Yulin is located in the Loess Plateau in northwest China, in the transition zone of the arid and semi-arid, agriculture and animal husbandry, the natural ecological environment is very fragile. At the same time, the development of economic is over-reliance on coal, oil and other energy, causing environmental pollution, ecological degradation, soil erosion and other issues.Based on the premise of the above social context and ecological problems, taking the northern Shaanxi------Yulin as the research object in this paper; first of all, through interpretation the of remote sensing images, access their land use, and analysis the spatial and temporal variance from terms of size and structure, the extent of land use, land transfer, the regional differences. Second, select 30 index from the social, economic, land and water resources, science and technology as well as the ecological environment total of five systems, using a composite weighting method to calculate the evaluation value of land comprehensive carrying capacity in Yulin city and counties, then analysis its temporal and spatial variation. Finally, analysis the problems during the using process of land resources; and proposed the regulation of sustainable land use from perspectives of macro and micro. The main conclusions are as follows:(1) During 1990 and 2012, the change of numbers and structures are quite different in Yulin area. However the arable land show a decreasing trend, its proportion decreased from 41.34% to 24.06%, a total reduction of 743040.2hm2; woodland is always increased, a total increase of 1257127.9hm2 during the 22 years; the grass in the first was increased and after decreased, totally reduced 249314.2hm2; water is decreased first and then increased, totally increased 8045. 1hm2; and the construction land is an increasing trend, which rose from 0.13% to 4.14%; unused land is a decreasing trend.The annual rate of the change is also quite different, where arable land, unused land, the grass is reduced, the annual rate of change are-1.90% -3.42% and -0.66%; but the woodland, water, construction land is increased, due to the base of the construction land is small, so the annual rate of change is up to 144.28%, the annual rate of change of forest land and waters are 34.96% and 0.69% respectively.(2) the overall index of land use is rising in Yulin area, from 227.827 in 1990 to 228.925 in 2012, indicate its the land use being a rising development period. Wherein Suide, Yuyang, Mizhi, Wubu, Hengshan et increased considerably, indicating its land develop rapidly; however Fugu, Qingjian, Shenmu Jiaxian et reduce more, indicating its land recession faster. At the same time, the transfer of various types of land in Yulin is various great; the most of arable land and grassland turn out is woodland, the most of woodlands and waters turn out is the grass, the most of unused land turn out is arable land; around the turn in of the various land, the most of arable land, woodlands and waters turn in are the grass, the most of grassland turn into is the arable land, the most of construction land turn into is unused land, the most of unused land turn into is woodland.(3) During 1990 and 2012, the land comprehensive carrying capacity of Yulin area fluctuating upward trend, the land comprehensive carrying capacity of county regional are quite different. The land comprehensive carrying capacity in 1990 is the smallest, is 0.201, in a serious overload condition; recently rose to 0.518 in 2008, in a substantially equilibrium state; in 2012 is the maximum, its value is 0.744, in a safe carrier state. The land comprehensive carrying capacity of Yulin county is generally increasing trend, but the county district vary greatly, and the spatial differentiation is obvious; wherein, the evaluation value of the county area in 1990, in seriously overloaded and critical overload state; by the year 2000 still Hengshan and Zizhou counties in the state of seriously overloaded, and the remaining ten counties is still in a state of critical overload; in 2012, the evaluation value of county area has been greatly enhanced, which only Jiaxian and Zizhou in the critical overload condition, while, the four counties of Jingbian County which in west, Yuyang, Shenmu, Fugu which in northern, are in a bearer safe state, the remaining six counties in the basic balance station. From the change of the magnitude and rate in the counties, the Shenmu, Jingbian Fugu and Yuyang changed greatly, but Jiaxian, Zizhou and qingjian changed little.(4) There are many bad problems in Yulin area when we use the land resources.First, the arable land was decreasing, among 22 years the arable land was reduced by 743,000 hm2; second, the construction land is increasing rapidly, construction land area in 2012 are 32.74 times in 1990; once again, the vegetation are destroyed, and the proportion of grassland is decreased much more; Finally, soil erosion and desertification is more serious. Afterwards from the aspects of macro and micro, put forward the regulation proposals of the land sustainable use, there are resource-based regulatory proposals, including increased land remediation and reclamation, to strengthen soil and water conservation measures, the development of unused land, land conservation and intensive utilization; the structured regulation proposals:control population, adjustment three industrial structure, strengthen environmental protection and ecological compensation mechanism; the technical regulation recommendations include that:to establish eco-agricultural park, ecological economy horticulture, recycling industrial park and develop the specialized tourism.The innovation of this paper is putting the land as a comprehensive and open system, when we study land comprehensive carrying capacity of Yulin area, at the same time, put the social, economic, land and water resources, science and technology level, environment totally five systems included in the land system, avoiding the deficiency of the traditional sense which only surrounding arable land——the food——the population. While using the AHP decision analysis and improved entropy method, avoiding the shortcomings of using a single weighting. At the same time, from the two perspectives of the macro and micro, practically put forward the regulate recommendation to improve the land comprehensive carrying capacity of Yulin area. |
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