| With the rapid development of industrialization,urbanization and agricultural modernization,the format,degree and structure of land use tend to be diversified and the development diversity targets of social economy and natural environment lead to the diversification of land use function.However,unreasonable land utilization process causes the contradiction between social economy and ecological environment.The problems such as soil pollution,soil erosion,and the reduction of cultivated land are becoming more and more serious.The problems of food and ecology have become important factors that threaten the healthy development of the social economy and ecological environment.Ecological restoration is one of the important ways to adjust the structure and function of terrestrial ecosystem to cope with the excessive disturbance of land use,which made the land use structure optimized gradually and the ecological environment quality enhanced greatly.Therefore,scientific and effective identification of land use change and its impact on ecological environment under the background of ecological restoration,avoiding the ecological risks in the process of land use and scientific and rational land use regulation have positive significance to achieve the landscape sustainable development.The Loess Plateau is one of important ecological fragile areas in China.The socio-economic development of the situation has put enormous pressure on the ecosystem,such as regional cities relatively dense,densely populated,industrial agglomeration.And the ecological problems such as soil erosion,land desertification and soil pollution are becoming more and more prominent in the process of unreasonable,unsustainable structure and unequal structure land use.However,ecological restoration project has impelled the optimization of land use structure gradually and the ecological environment has been improved after years of ecological restoration.Yan'an city,which is the key demonstration area of ecological restoration of the Loess Plateau,based on the current situation and characteristics of regional land use,positively responded to the national ecological restoration policy,and its regional ecological environment quality has been improved remarkably.Based on the background of ecological restoration,the main line of this paper,taking Yan'an City as typical area,which is located in the middle and south of the Loess Plateau,is land use "change-mechanism-effect-optimization" research.The landscape zoning which is based on the analysis of land use change,driving mechanism and ecological effect was used to explore the different scale of landscape sustainable model.This paper can provide a scientific reference for its reasonable and efficient ecological restoration and ecological environment protection,which can promote regional socio-economic and ecological environment coordinated and sustainable development.The main conclusions of this paper are as follows:(1)Temporal and spatial characteristics of land use change.The land use of Yan'an City has changed significantly,ecological restoration has significant spatial differentiation,and the land use transformation has the direction and difference under the background of ecological restoration.The main base of Yan'an City was cultivated land,forest land and grassland during from 2000 to 2015,whereas the area of cultivated land decreased rapidly,the area of forest land increased greatly,and the area of grassland increased steadily.The area of ecological restoration increased with the increase of elevation and slope,and ecological restoration area was mainly concentrated in the elevation level II(925-1115m),III(1115-1275m)and IV(1275-1442m)and slope of 6~15,15~25,which account for more than 70% of the area.The difference spatial pattern of land use which the cultivated land of north is more than its in the south,the forest land of south is more than its in the north and the grassland is relatively uniform made the conversion of the cultivated land into the forest land and grassland is relatively large in the north,and the degree of conversion to woodland and grassland is relatively small in the south under the process of ecological restoration.The conversion of cultivated land to forest land and grassland was accounts for 94.26% of the total area.(2)Study on driving mechanism of land use.The land use process has resulted in significant changes in land use types due to the combination of natural factors,human factors and policy factors in Yan'an City under the background of ecological restoration,and the influence of each factor on the change of land use type is different.From the comprehensive role of the driving factors,the change of cultivated land were mainly due to the change of GDP per capita and the distance to the nearest rural residential area;the change of forest land was mainly due to the distance from the nearest rural settlements,the change of the total population density,the average annual growth rate of GDP and the distance to the nearest road;the change of grassland were mainly due to changes in GDP,slope,total population density,elevation and distance to the nearest county level;the change of construction land were mainly due to elevation,to the nearest county center distance and the average GDP changes and other factors combined effects.From the cultural factors of cultivated land changes,the total population,per capita GDP,the output value of the secondary industry and its share of GDP are negatively correlated with the change of cultivated land.However,the agricultural population,farmers net income,fixed asset investment and arable land area change has a positive correlation with the change of cultivated land.Land use change is the process of interaction between humanities and policy factors under the influence of natural factors.It is reasonable to manage and control the driving factors,which can effectively promote the intensive use of land resources and the sustainable development of society,economy and ecosystem.(3)Temporal and spatial characteristics of ecological effects.The net primary productivity and ecosystem service function of Yan'an City increased under the background of ecological restoration,but the process of change had significant spatial and temporal difference.From 2000 to 2013,the NPP in Yan'an City showed a trend of fluctuation,and the average value of NPP increased by 68.053%,while the NPP showed a decreasing trend from south to north.The slight increased area of NPP in Yan'an City was the largest area,while the slight decreased area and the significantly increased area were relatively small.However,the basically unchanged area,mild increased area and moderate increased area of NPP in Yan'an City is account for 95.980%.From 2000 to 2015,the value of ecosystem services in Yan'an City increased from 24.476 billion to 26.472 billion,which the growth rate was 68.155%.The function of ecosystem services in all districts and counties was gradually increased,and its function generally showed a decreasing trend from south to north,but the degree of difference was reduced.From 2000 to 2015,the ecosystem functions of regulation function,support function,supply function and cultural function in Yan'an City were increased,but The degree of functional difference was gradually decreased,and its proportional relation was 17.560: 11.844: 3.586: 1.000.(4)Analysis of Sustainable landscape pattern.From the perspective of land use characteristics,landscape pattern differentiation and ecological service function,the landscape of Yan'an City can be divided into four regions by using the system cluster model,wich can explore the sustainable landscape type from two aspects of city and county.The sustainable landscape development of city should set optimal development zones,key development zones,restricted development zones and banned development zones based on the scientific analysis of the social economy and the natural environment of the city,which they can balance the agricultural land,construction land and unused land,and coordinate the various elements of land use system.The sustainable development of county should guide the transformation of cultivated land,optimize the forest land and grassland utilization structure,scientifically optimize the land use of urban land,industrial land and rural residential land,and strengthen the intensive use of construction land.Meanwhile,this paper also puts forward some measures which is continuously to promote the ecological restoration project,rationally and orderly optimize the agricultural land structure,promote the intensive use of construction land,balance the economic and ecological benefits scientifically and strengthen the function of ecological system to ensure the sustainable landscape development. |
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