| As the main body of urban natural productivity,urban greening land is an important component of urban ecosystem,which plays an important role in improving ecological environment and maintaining ecological balance.Quantitative analysis of the landscape pattern of urban greening land from the perspective of landscape ecology is the main research direction at this stage,but the traditional two-dimensional perspective is not enough to reflect the actual landscape characteristics.Taking Dalian as an example,this paper uses digital elevation model(DEM)to extract the three-dimensional number of greening land in the three districts of Dalian in 2000,2005,2010 and 2015 through ArcGIS.According to the results,the mathematical statistics are carried out.Through the dynamic degree of greening land and the transfer model of the center of gravity,the spatio-temporal dynamic change characteristics of greening land were studied;the evaluation indexes of fragmentation index,shape index and three-dimensional greening ecological index were constructed respectively,and the index values of each area were studied by comprehensive factor evaluation method;the landscape scale index,shape index and grid of urban greening land were selected by using the principles and methods of landscape ecology.The local index and ecological greening index totaled 15 indices.Streets were taken as calculation units to analyze the results of spatial-temporal differentiation and spatial autocorrelation.The fragmentation index,shape index and ecological greening index of greening land were analyzed by using geographic weighted regression model and data from 2015 as an example.The main conclusions are as follows:(1)The green land patches in the study area mainly consist of large patches and super-large patches with a large area but a small number,and the total area of small and medium patches with a large number is limited.The number and area proportion of large and super-large patches in the whole region showed a downward trend,and the number of small and medium-sized patches was increasing.It shows that the homogenization degree of plaques has been improved,but the dominant situation of large and super-large plaques has not changed fundamentally.(2)The central point of greening land is located in Bayi Street in the southeastern part of the study area,which is in the direction of shifting from northeast to Southeast and then to northwest,with the longest distance from 2005 to 2010.It shows that the spatial distribution of green space is mainly concentrated in the southeastern region,and this spatial distribution situation is relatively stable.The positive growth rate of the dynamic degree of greening land is slowing down,and the positive growth is turning to negative growth,which indicates that the overall level of urban greening has improved,but it still needs to protect and strengthen its healthy development trend.(3)The spatial differences and spatial aggregation of each landscape index are significant.Among them,the scale characteristics of greening land are generally higher in the South and lower in the north,higher in the north and the east,and the fragmentation gradually decreases from north to south.The patch shape tends to be more complex and fragmented in time.The ecological indicators are generally stable,and the spatial differences are also significant.According to the spatial autocorrelation analysis,the spatial correlation of landscape index in each year is obvious,and it has spatial aggregation characteristics.(4)Road density,building density,average topography and population density have different effects on landscape pattern differentiation characteristics of urban greening land.Among them,the fragmentation degree and shape characteristics of green patches are significantly affected by architecture and topography,and the ecological greening index is significantly affected by four factors.Overall,the study of landscape pattern of urban greening land from three-dimensional perspective,the selection of diversified indicators,the quantitative analysis of the results of indicators,the study of its spatial and temporal differentiation characteristics and the multi-factor analysis of influencing factors will help to comprehensively and scientifically study the characteristics of urban greening land,and provide a reference for the rational planning of urban greening land and the evaluation of the status quo of urban greening land. |
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