| In the context of rapid urbanization and environmental change, the land use imposed an adverse effect on socio-ecosystem as an environmental hazard while being used as an import resource. As the acceleration of land-use type change and the intensification of land use, the ecological risk of land utilization is increasingly prominent. The social and economic development in Changsha-Zhuzhou-Xiangtan Urban group is so rapidly that the problem of the land ecological risk deserves more attention. The connotation of ecological risk due to land use was extended and principal component analysis and data envelopment analysis (DEA) was coupled to evaluate the ecological risk while a structural equation modeling was used to track the mechanism of ecological risk change triggered by the land use dynamic.The main results are as follows:(1) The temporal and spatial feature of land utilization change in Changzhutan is obvious. The agricultural land is decreasing in Changsha and increasing in Xiangtan and Zhuzhou, in addition, the construction land is sprawling and unused land is losing in whole Changzhutan. the change can be characterized with positive dynamic degree of agricultural land use in Changsha and negative ones in zhuzhou and Xiangtan cities, as for the whole city group of Changzhutan, the positive dynamic degree in construction land while a negative ones in unused land.the unused land change is the most biggest and the farmland is smallest and construction land is in the middle.(2) The main indicator describing land use change of Shangsha-Zhuzhou-Xiangtan Urban group, is to increase agricultural land, land utilization ratio,the consolidation ratio of agricultural land, the class ratio of the natural and economic interaction, per capita arable land, land reserve resource, soil coordination index, and effective irrigation area; The main risk factor caused by land utilization change in Changzhutan is the water-soil loss rate, land contamination, urban sprawling level, transportation density, agricultural pesticide and fertilizer severity, waste gas and waste discharges are identified as the main ecological stressors.(3) During the period of research, the land ecological risk of Changzhutan are different in temporal and spatial change.The degree of land ecological risk in Changzhutan in 2005 follows the descending order：Changsha city (0.6223), Xiangxiang city (0.6069), Wangcheng district (0.5910), Ningxiang county,(0.5692), Liuyang city (0.5489), Zhuzhou city (0.5292), Changsha county (0.5134), Chaling county (0.5062), tiling city (0.4899), Xiangtan county (0.4805), Youxian county (0.4363), Shaoshan city(0.4329), Zhuzhou county (0.4244), Xiangtan city (0.4136), YanLing county(0.3712). While the order in 2011 is rearranged as the following:Changsha county (0.6472), Liuyang city, (0.5881), Yanling county(0.5694), Xiangtan county (0.5508), Chaling county (0.5262),Zhuzhou city (0.5152),Zhuzhou county (0.4905), Shaoshan city (0.4878), Ningxiang county (0.4833), Youxian county 0.4770), liling city (0.4652), Changsha city (0.4652),Xiangtan city (0.4373), Wangcheng district (0.3999), Xiangxiang city (0.3846).(4) In terms of the regional characteristics of land use ecological risk, five categories are listed:the first category of land use ecological risk in 2005 is the Xiangxiang, Changsha city and Youxian country,;the second category is Ningxiang, Chaling, Changsha country, Xiangtan city, Zhuzhou city; the third class is Zhuzhou county, Shaoshan city, Wangcheng country, Liling and Liuyang city; the forth class is YanLing; the fifth class is Xiangtan county. The regional number configuration is 3:5:5:1:1; while the first category of land use ecological risk in 2011 Changsha, Shaoshan city and Chaling county;the second category is Wangcheng district, Xiangxiang country and Liling county; the hird class is Liuyang city, Xiangtan county and Ningxiang county;the forth class is Zhuzhou city and Xiangtan city; the fifth class is Changsha country,YanLing county, Zhuzhou county, and Youxian country. The regional number configuration is 3:3:3:2:4.(5) The fluctuation of ecological risk levels from 2005 to 2011 is obvious either in whole Changzhutan area or in separate region. Each city contributes to different weights of influence on the ecological risk in Changzhutan, of which Zhuzhou has the great coefficients of contribution (0.450), followed by Changsha (0.376) and Xiangtan(0.187) in 2005 while the contribution coefficients are 0.617,0.607 and 0.565 in Changsha, Zhuzhou and Xiangtan in 2011,respectly. A rank sum of score of the land ecological risk assessment is computed by DEA:the score in 2005 is 339 and the score in 2011 is 126; A conclusion that the ecological risk of land use in 2011 is more than that in 2005. is drawn from T statistics of DEA rank sum test.(6) Land use is both driven by natural and social economy, and in research time socio-economic factors are the most driving forces of ecological risk due to land use change, of which the rapid urbanization and economic development hold the larger share. In terms of direct driving forces, the social and economic impacts are the largest, and natural factors influence the smallest. But for the analysis of total driving force, social and economic factors are still the greatest influence, the smallest is the effect of land use change. For ecological risk of land use control, temperature and precipitation element is an exogenous variable; human can only adopt an adaptation.However per capita GDP, tertiary industry GDP, urbanization of population should be increased. Total population, population density and per capita constructional land need to be controlled moderately.The paper’s highlights lie in the expansion of the ecological risk domain and application of data envelopment analysis and structural equation modeling for ecological risk estimation and its mechanism, The results have import implication of land use policy making for reducing ecological risk... |
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