| Based on industrialization and urbanization of urban agglomerations,the contradiction between urban economic development and ecological protection has also intensified,leading to the rising threat of urban diseases such as haphazard development of cities,waste of resources and environmental pollution,which directly affect human well-being.Land use optimization is a major effort to ensure the high-quality development of urban agglomerations.Faced with the new territorial and spatial planning system,how can we balance land use and development and ecological environmental protection,and find an equilibrium between the two,is an urgent problem that needs to be addressed for current regional high-quality development.Urban agglomerations are areas where land use changes are highly active,and their impact on the ecological environment is getting increasingly stronger.How to carefully weigh the relationship between land use and development and ecological environment protection is a scientific issue that must be tackled with high regard in land use optimization.In view of this,this study took Changsha-Zhuzhou-Xiangtan(CZT)urban agglomeration as the research object,and adopted research methods including land use intensity(LUI),fuzzy evaluation model,Integrated Valuation of Ecosystem Services and Tradeoffs(In VEST),multi-objective function,Future Land Use Simulation(FLUS),etc.On the basis of the analysis of land use change,ecological environment quality status analysis,and spatio-temporal simulation of land use pattern,an optimized framework for land use was then constructed,which can be adequate to provide a management and control basis for the harmonious man-land development of regions,and also provide theoretical support for building a spatially high-quality urban agglomerations.The main results of the paper found:(1)In terms of structure and intensity,the area of forest land,arable land and grassland in CZT urban agglomeration presented a downward trend from2000 to 2017,and the dynamics of various land use types varied greatly in different periods.There are dynamic changes in various types of land use intensity,and the proportion of the area of each intensity varies in different periods.The overall trend is that the proportion of high-intensity and low-intensity areas greatly expanded.And that of medium-high-intensity areas increased slightly,while the proportion of medium-low-intensity areas rose significantly.With regard to land use type area changes,forest land and arable land area declined most dramatically.Specifically,the proportion of forest land area in total area fell the most,the one of arable land area came second,and the decrease in grassland area was relatively small.The area of construction land has increased the most.As for the temporal changes of land use intensity,there is certain dynamic change in the area proportions of various intensity types in this urban agglomeration.The general trend is that the proportions of high-intensity and low-intensity areas have gone up significantly,and that of medium-high-intensity areas has increased slightly.The proportion of medium-low-intensity area has greatly dropped.There is obvious spatial agglomeration in land use intensity,and the spatial agglomeration is dynamic in time series.In terms of spatial distribution,high-intensity areas are concentrated in the urban areas of Changsha,Zhuzhou and Xiangtan cities,whose area has increased significantly from 2000 to 2017,rapidly expanding to Yuelu District,Wangcheng County,Changsha County,Yuhu District,Tianyuan District and Liling City.Medium-high-intensity areas are mainly in the periphery of high-intensity areas,such as Liuyang City,Ningxiang County,Liling City,You County,Chaling County,Xiangxiang City and Xiangtan County in the periphery of the three cities of Changsha,Zhuzhou and Xiangtan.Medium-low-intensity districts have the widest spatial distribution.From 2000 to 2017,they were mainly distributed in remote rural areas far from urban areas and towns,with little spatial change.The low-intensity distribution is very scattered,dotting in the gaps of the other three land-use intensity areas.Its space changes are not so distinct.(2)According to Pressure-State-Response(PSR)system,the comprehensive index of the ecological environment of the CZT urban agglomeration basically increased from 2000 to 2017,but there are differences between regions,and the quality of the ecological environment of some counties(cities,districts)has declined.In terms of temporal changes,the ecological pressure index of the urban agglomeration during the study period showed an overall upward trend.In addition,the ecological state index and ecological response index mostly demonstrated a rising trend.In terms of spatial distribution,the spatial distribution of the three indexes of pressure,state,response and the comprehensive index are all notably unbalanced.The high values of the pressure index are concentrated in the core area of the CZT urban agglomeration,that of the state index are mainly distributed in the southern area of the urban agglomeration,the ones of the response index are gathered in the core area of the CZT urban agglomeration as well,and that of the comprehensive ecological environment quality index is distributed in the northeast and southeast of it.In terms of influencing factors,the quality of the ecological environment is closely related to human activities,such as resource and energy consumption,pollutant discharge,ecological environment construction and governance investment,etc.Specifically,the intensity of land use has a relatively great effect on the quality of the ecological environment,and the proportion of ecological land has also a significant impact on it.(3)As far as ecosystem service is concerned,the four phases of remote sensing interpretation results in 2000,2005,2010,and 2017 were utilized as the data source,and four services including habitat quality,food supply,carbon storage and soil conservation were selected to analyze the ecosystem service response to changes in land use in the CZT urban agglomeration,along with use of methods like ecosystem service value calculation,cold/hot-spot detection and spatial autocorrelation.In terms of time series,the four ecological services generally exhibit a trend of decrease in habitat quality and carbon storage services as well as an increase in food supply and soil conservation services,but there are also individual differences.Spatially,there are significant dissimilarities in distribution,and the overall spatial distribution of habitat quality and carbon storage and soil conservation services shows a strong similarity,while the spatial distribution of food supply services contrasts with that of the former three services.In terms of spatial correlation,the cold/hot-spot distribution of habitat quality and carbon storage services in the study area are quite similar through the detection of cold and hot spots,and the distribution of cold and hot spots in soil conservation services also shows similarity.The one in food supply,however,is in contrast to that of the first three.Local binary spatial auto-correlation analysis shows that there is a significant spatial auto-correlation between land-use intensity and the four ecosystem services,which can be divided into four typical types i.e.high-high agglomeration,high-low agglomeration,low-high agglomeration,and low-low agglomeration.(4)Land use simulation based on multi-objective function and FLUS model found that the comprehensive benefits of land use under the medium ecological constrain scenario are the highest.Since population and economy have become the main determinants of land use change in urban agglomerations.The medium ecological constrain scenario aims at highest efficient of land use,after the use of multi-objective function models to predict time-based land use structure,it was noted that the overall ecological and economic benefits came first in the medium ecological constrain scenario.Therefore,scenario 2 is the optimal one as far as benefit is concerned.In terms of influencing factors of land use change,population and economy have become the main ruling power of land use change in urban agglomerations.And the mechanism of internal force,external force,and policy force was constructed.In detail,the internal driving force is the internal attribute that determines the land use change,and the external driving force is the direct drive to promote the land use change,and the policy force is the driving effect of ecological,land,economic conditions.In terms of land use spatial simulation,the overall accuracy of the FLUS model simulation is 86.62%,indicating that the model is of high accuracy in simulating land use changes in urban agglomerations,and,meeting the research requirements. |
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