| As a comprehensive reflection of a certain regional ecological environment,landscape pattern plays an important role in understanding the regional ecological and evolution process.At present,with the rapid development of social economy,the depth and breadth of the impact of human activities on the natural ecological environment continue to expand,and the objective impacts on land use landscape patterns and the resulting ecological problems have increasingly drawn the attention of experts and scholars.Therefore,it is of great practical significance to understand and master the change characteristics and spatial gradient change rules of land use landscape pattern with the change of time to maintain the dynamic balance of regional ecology,improve the regional ecological environment and realize the sustainable development of land resource utilization.In this study,the Chongqing section of the Three Gorges Reservoir area,which is the combination of high intense human activities and fragile ecological environment in“One metropolitan area and‘two city agglomeration'(Northeast and Southeast of Chongqing)”of Chongqing City,is taken as the research area.After the precision identification and processing of the remote sensing images obtained from the Chinese Academy of Sciences in 1995,2005 and 2015,the maps of the land-use landscape types in the three time periods of the study area were interpreted,including 9 land types:grassland,water and construction land,paddy field,dry land,high-density vegetation covered forest,medium density vegetation covered forest,low-density vegetation covered forest and unutilized land.ArcGIS,Fragstats and other softwares were used to calculate and analyze the land use landscape pattern in Chongqing section of the Three Gorges Reservoir area.First of all,the information of various landscape elements and land use transfer matrix of each year in the study area were calculated and sorted out,and the change characteristics of each landscape element in the past 20 years since Chongqing became municipality and the construction of the Three Gorges Reservoir area were analyzed.At the same time,the appropriate indicators are selected at the landscape level and the type level respectively to calculate and analyze the spatial and temporal variation of the landscape pattern in the study area.Secondly,in order to further analyze the impact and driving force of human activities on the landscape pattern of the study area,the night light data was introduced,combined with overlay analysis and gradient analysis,to study the spatial-temporal differences of the landscape pattern based on the landscape level and type level under the interference of human activities.Meanwhile,the driving forces of landscape change were analyzed by projection pursuit model.Finally,based on the CA-Markov model,taking the land use landscape pattern data in the study area in 2015 as the base data,the land use landscape pattern in2025 was simulated and predicted,the landscape change trend of the reservoir area in the future period was explained,and the problems and countermeasures for ecological protection of the reservoir area were put forward.The results are as follows:(1)In Chongqing section of the Three Gorges Reservoir area,dry land and medium density vegetation covered forest are the main landscape types.Paddy fields,dry lands,and forest with various density vegetation cover more than 80%of the total area,and the area of construction land has changed the most,from 304.71 km~2 in 1995 to 1406.28 km~2 in 2015,an increase of more than three times.In the past 20 years,the largest transfer out area was from grassland.The area of construction land,water,and forest cover of various densities increased in varying degrees,and there was a trend of“small transfer out,large transfer in”.The fragmentation of grassland has increased significantly.The landscape of paddy fields,high-density vegetation-covered forest,low-density vegetation-covered forest,water,and construction land has become more regular,and the rest of the landscape types have become more complicated.At the landscape level,the overall landscape fragmentation in the study area has increased,the distribution of landscape patches is more balanced,the connectivity between the patches has increased,and the landscape concentration has increased in the past 10 years.(2)There are significant differences in the spatial distribution of human activities in Chongqing section of the Three Gorges reservoir area decreases gradually from west to east.The areas with high intensity of human activities are concentrated and distributed finely.The areas at the end of the reservoir are centered in Yuzhong District,showing a decreasing trend in circles.The intensity of human activities in the hinterland of the reservoir is relatively weak,and the intensity of human activities in the main river basin of the Yangtze River is stronger than that in the surrounding areas.Under the interference of human activities,the landscape pattern of the study area changes gradiently with the intensity of human activities.At the landscape level,with the increasing intensity of human activities in the reservoir area,the landscape diversity and evenness index of the study area showed a trend of increasing first and then decreasing,which was consistent with the intermediate disturbance hypothesis that moderate disturbance is helpful to landscape optimization.The number of landscape patches decreased significantly,and the closer to the areas of high intensity of human activities,the lower the number of patches.The aggregation degree of landscape patches first decreased and then increased,and the overall distribution of landscape patches tended to be centralized.The overall connectivity of the landscape was good but decreased.The patch density increased first and then decreased,but the overall patch density still increased slightly.The degree of landscape fragmentation increased,while in 2015,the degree of landscape fragmentation in high-intensity human activities area decreased.On the level of type,the four landscapes of construction land,water area,grassland and low-density vegetation covered forest land with the largest change were selected for comparison.The change trend of four kinds of landscape features was similar under the interference of human activities.The closer the area percentage,patch density,and maximum patch index of each landscape type to the area of high-intensity human activity,the more drastic the changes,and the three other landscape types except grassland became more fragmented.The change of the three indicators also showed that the difference of spatial change between different landscape types in different intensity zones.The landscape shape index and the average patch dimension decreased with the increase of human activity intensity,and only the average patch dimension value of construction land increased slightly.In general,landscape shape tended to be regular and simple,while in high-intensity human activities,the large increase of construction land led to the complexity of landscape shape.In the past 20 years,the driving force of landscape change in Chongqing section of the Three Gorges reservoir area has shown the stability of the spatial region and the dynamic of the time series.The driving mechanism has gradually evolved from the"livelihood economy"driven by the factors of economy,life,population and transportation to the multi-factor synergy drive today.The driving force of landscape change in the main urban areas of Chongqing,Changshou,Jiangjin,and other places,as well as near Wanzhou in the storage hinterland area,is strongly driven by urban construction land,while the driving force of landscape change in all districts and counties in the northeast of Chongqing is weak,which is mainly driven by forest,grassland and water.Other regions are relatively complicated,showing a pattern of multiple types of landscape change driven coexistence.(3)The simulation and prediction of the landscape pattern of the Chongqing section of the Three Gorges Reservoir.The CA-Markov model was used to simulate and predict the landscape pattern in the study area in 2025.The results showed that:in terms of quantity,the area of construction land would increase the most,the area of grassland,paddy field,and dry land would further decrease,and the landscape area of each forest land would increase steadily.On the landscape index,the degree of landscape fragmentation in the study area was going to improve,as well as the diversity and evenness of the landscape.The overall trend would be balanced,and the dominant landscape was going to weaken.Based on the simulation results,the following problems and suggestions are put forward for the development of the reservoir area:1)Protection policies should be formulated in time to prevent further reduction of grassland;2)While the water area is increasing,the management department should focus on the quality of water body and pay equal attention to both quantity and quality;3)The overall land use plan of the reservoir area should be scientifically formulated,the construction land growth boundary should be strictly controlled,the red line of farmland protection should be rigorously observed,the effectiveness of land remediation projects should be strengthened,the quantity of cultivated land should be ensured,and the contradiction between human and land should be improved;4)To maintain the area of forest,make full use of unused land,improve the overall social and economic benefits and land use efficiency of the reservoir area. |
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