Study On Landscape Pattern Changes And Ecological Cumulative Effect Of Major Urban Expansion Areas In Chengdu

Urbanization is a process of landscape type change with human subjective active activities as the main body.The process of its competition involves spatial competition between artificial landscapes and natural resources,thereby destroying the structural stability and ecological functions of regional ecosystems.A variety of ecological and environmental problems are caused,which poses a huge threat to the ecological health of urbanized areas.The ecological environment is closely related to the sustainable development of mankind.In order to ensure the harmonious coexistence of man and nature and maintain regional ecological security,the landscape ecological pattern must be continuously optimized in the process of urbanization,and the development needs of urban expansion and ecological protection must be balanced to promote the scientific development of urbanization.In particular,the proposal of ecological civilization construction highlights the significance of ecological environment in social development and progress.As one of the central cities of the national-level urban agglomeration,Chengdu has an urbanization rate of over 70% in 2017,which has reached the level of developed countries.The national ranking of social and economic development ranks high,and the impact of urbanization on the ecological environment is becoming more and more significant.Therefore,this paper takes main urban expansion area in Chengdu as the research area,and uses three phases of remote sensing high-resolution images from2003,2010,and 2017 as data sources.First,it uses landscape structural indicators to characterize the landscape pattern of the main urban expansion area in Chengdu.Analyze,then use the landscape pressure index method to improve the evaluation method of ecological cumulative effects,and finally establish an ecological cumulative effect model to study the ecological environment impact of the study area,and use the results to explore how to improve the disadvantages of urban development in the study area sexual development recommendations.The main findings are asfollows:(1)In terms of landscape pattern changes,the landscape structure of the study area changed strongly from 2003 to 2017,and the evolution of the urban and arable land landscape structure dominated.The area of the urban landscape has increased and the degree of fragmentation has increased.There are increasing marginal effects around the urban landscape,and ecological mobility has increased significantly.The cultivated land landscape tends to be fragmented,the patch area is continuously reduced,and its material energy contribution rate and ecological mobility are reduced.The urban landscape of the northeast urban expansion area gradually dominates,the dominant position of cultivated land continues to decline,and the forest and grassland landscape tends to be broken.The urban and village landscape patches in the northwest urban expansion area have expanded significantly,forcing the proportion of cultivated land structure to decline,and the stability of forest and grassland structure is good;the landscape structure of urban landscape and cultivated land landscape in the western urban expansion area increases and decreases,and the fragmentation of the village landscape pattern increases;the degree of fragmentation of the urban landscape in the southwestern urban expansion area is higher,and the number structure of village patches needs to be improved;The proportion of urban landscape in the southeast urban expansion area has been expanding,and the layout is more reasonable.The agglomeration of forest and grassland landscape structure has increased,and the cultivated land layout has gradually become fragmented.(2)On the characteristics of ecological cumulative effect,the cumulative size relationship between the ecological service function deviations of each urban expansion area is expressed as the southwest urban expansion area,the southeast urban expansion area,the northeast urban expansion area,the western urban expansion area,and the northwest urban expansion area.The cumulative index of landscape oppression in the study area is 0.0388,and the phenomenon of landscape oppression in forest and grassland is the most obvious.The southwestern urban expansion area and the northeast urban expansion area are high-risk areas for landscape oppression.The southeast urban expansion area and the northwestern urban expansion area are medium-risk areas for landscape oppression.The urban expansion area is a low-risk area of landscape oppression.The cumulative index of vegetation cover evolution in the study area was 0.1188.The deterioration of regional vegetation cover was dominated by the cumulative impact of cultivated landscape vegetationcover evolution.The western urban expansion area is a heavily cumulative area of vegetation cover evolution.The northwestern urban expansion area and the southwestern urban expansion area are moderate vegetation cover evolution accumulation area.The northeast urban expansion area and the southeast urban expansion area are the areas of slight accumulation of vegetation cover evolution.(3)Regarding the impact of ecological cumulative effects,the index of ecological cumulative effect of the major urban expansion areas in Chengdu is 0.2198.The ecological environment in the study area has suffered a certain degree of damage,and the negative effect of cultivated land ecological accumulation are significant and expanding.Based on the nature of the ecological cumulative effect of each urban expansion area and the differences in artificial landscape expansion modes,the southwest urban expansion area,the northeast urban expansion area,and the southeast urban expansion area are backfill urban expansion areas.The ecological environment in this area has obviously deteriorated.In the future,it should rely on the improvement of traffic conditions,internal optimization and adjustment of urban land use and intensive use to promote the concentrated and continuous development of urban construction land in order to promote economic and social development to the greatest extent,and to minimize damage to natural habitats.The western urban expansion area and the northwestern urban expansion area belong to the sprawling urban expansion area.The research results show that the ecological environment of the area is maintained well,and there is no obvious damage phenomenon.In the future,we should improve the quality of the ecological environment with higher standards,appropriately adjust the layout structure of urban land and road land,promote the rational allocation of land resources,avoid urban "spread" development,and focus on optimization and improvement in the layout design of villages,arable land and waters.