| Urbanization has profoundly changed the structure of land use,further affected the function of urban ecosystem,and related to regional ecological security and sustainable economic and social development.With the continuous improvement of economic and social fine management level,higher requirements are put forward for the supervision of urban land use structure,function and ecological security.It is of great scientific significance and practical value to accurately monitor the spatio-temporal pattern evolution of land use in the process of urbanization and accurately assess regional ecological security for promoting urban sustainable development.The research on land use change and its ecological effects caused by urbanization has the characteristics of great dynamic change and complex internal process of land use change.In recent years,the application of remote sensing technology has brought great convenience to urban dynamic monitoring,but different remote sensing information sources have different characteristics and advantages.Although the commonly used Landsat images have the advantages of long time span and continuous data,which are more suitable for long time series analysis,due to the limitation of data spatial resolution(30 m),Landsat series products can not meet the requirements of high-precision land use monitoring.ZY-3 is the first civil stereo mapping satellite launched by China in 2012.Its panchromatic band resolution is 2.1m,and it carries rich information of ground objects,including strong scene semantic information and current situation,which can better support the fine study of the spatial and temporal evolution of urban land use.The traditional classification method of urban land cover is to interpret the change of land use type by visual interpretation,supervised/unsupervised classification and other human-computer interactive interpretation methods,which can not fully tap the spectral,spatial,texture and other information of remote sensing images,and the classification accuracy can not meet the needs of the industry,and it is difficult to achieve regional scale.It is difficult to effectively support the precise control of urban land use elements.In addition,most of the existing studies focus on the retrospective analysis of historical data,and pay less attention to the simulation and prediction of the possible evolution of land use patterns under different development/planning and construction scenarios in the future,and even less attention to the possible ecological security consequences,which restricts the integrated and coordinated governance of land resources management and land spatial elements in the current and future periods.Based on the above understanding,this study selects Dalian Economic and Technological Development Zone(Dalian Development Zone for short),a typical urbanized area,as the study area.A medium and high resolution remote sensing image database consisting of Landsat images of 1984-2020 and ZY-3 images of 2002,2010,2015 and 2018 was established,using the technology of fine earth observation and remote sensing information extraction,taking advantage of the advantages of multi-source heterogeneous data in temporal and spatial resolution,coupling field survey data with in-depth learning algorithm,and through objectoriented technology,urban expansion trajectory is analyzed,urban land resources dynamics are monitored,its impact on urban landscape structure and ecological risk is assessed,and different levels of risk are identified and divided.The future urban expansion and its ecological security risks under various development modes are predicted,and the adaptive development strategies are put forward.The main research findings are as follows:(1)Based on Landsat,ZY-3 remote sensing images,topography,social and economic characteristics,urban infrastructure and other data,an annual continuous remote sensing monitoring database is established;The framework of Deeplab Xception network is constructed,and object-oriented image classification technology is integrated to achieve pixel-level semantic segmentation of remote sensing images,which improves the accuracy of urban land information extraction and the reliability of interpretation results,and overcomes the limitations of single data source and traditional land use information interpretation methods.It realizes more accurate identification of land use types in complex environments.The results show that the overall classification accuracy is greater than 90%,and the Kappa coefficient is greater than 0.87,which is more accurate than the interpretation results of the traditional supervised classification method.(2)The location and speed of urban spatial expansion are revealed from the aspects of quantitative structure of construction land,dynamic degree index and quantitative expansion measurement index.The results show that from 1984 to 2020,the center of gravity of Dalian development zone moved northward,the land use types showed a process of dispersionintensive,and the continuity of spatial distribution and regional coordination were significantly enhanced.Topographic conditions constrained the possibility of expansion of Dalian development zone,population growth and economic demand played a significant role in promoting the expansion of construction land,and the double-center urban pattern had been formed.(3)Using ZY-3 remote sensing images in 2002,2010,2015 and 2018,the moving moment of land use type is established,and the quantitative analysis of land use type development and moving model is carried out by using the mathematical method of space-self equality,so as to more accurately depict the spatial distribution,segmental and regular characteristics of landspace elements in the process of urbanization.The results show that from 2002 to 2018,the industrial land and residential land in the region remained constant,and the land used for production fluctuated greatly,which has become a typical feature of urbanization.(4)The Ecological Risk Index(ERI),which is a comprehensive index,is used to analyze the risk changes of landscape ecology under the urban space expansion,and the logical relationship between landscape structure and ecological risk is established.The results indicate that from 2002 to 2018,the overall low and medium risk areas in the study area increased and gradually gathered,while the high risk areas showed a fluctuating downward trend.(5)Based on the PLUS model,the urban expansion trajectory was predicted under current policy development scenarios,farmland protection scenarios,and ecological protection scenarios,and its ecological risks were evaluated.The simulation effect Kappa of PLUS model for 2010 and 2015 data validation is 0.83,which is ideal and the selected parameters and impact factors can meet the accuracy requirements of land use simulation.We simulated and predicted ecological risks in 2026 under three scenarios using 2018 data.The results indicate that under the current policy development scenario,the proportion of arable land and ecological land converted into construction land is high,and the ecological risk is relatively high;Under the scenario of farmland protection,the transfer of farmland is restricted,and the fragmentation of farmland landscape grid is significantly reduced;Under the ecological protection scenario,the minimum ERI value decreases,and the overall low risk areas of the city significantly increase.Ecological land and arable land resources have not been significantly compressed.Research further indicates that compared to the current policy development scenario and farmland protection scenario,the ecological protection scenario has the largest area of medium and low risk areas,and the medium and low risk areas form a significant degree of connectivity.The risk value shows a significant downward trend,and the construction land patches are more concentrated,and the landscape pattern is developing towards uniformity.(6)Based on the driving force and development trend of urban land use,from the perspective of resource protection and ecological and economic carrying capacity,this paper proposes planning strategies for the sustainable use of land resources in Dalian Development Zone.One is to strengthen the unity of urban land use planning,optimize urban functions and industrial structure,scientifically delineate three zones and three lines,establish planning guidance and control,and enhance the internal permeability and microcirculation capacity of the city.The second is to adhere to intensive land use and effectively implement the protection mechanism for basic farmland.The third is to control the scale of urbanization expansion,adjust the land use structure of urban-rural integration,and improve the resilience,adaptability,and carrying capacity of national land space.The fourth is to implement ecological restoration projects for fragile areas such as damaged and degraded ecosystems,promote joint protection and governance of the ecological environment,and improve the urban ecological network. |
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