Research On The Spatio-temporal Evolution And Differentiation Of Urban Landscape Lakes In The Yellow River Basin

As the core resource in the process of urban development,the in-depth study of its spatio-temporal pattern evolution characteristics and differentiation mechanism is conducive to the necessary and reasonable regulation of wetland protection and ecological governance in the Yellow River basin according to the objective law,and accelerate the protection and restoration of mountains,forests,lakes,grass and sand.This paper extracts the elements of urban landscape lakes in the Yellow River Basin.Based on Landsat image data,and constructs the analysis framework of"pattern-evolution process-mechanism".Using dynamic degree,change intensity index,GIS spatial analysis,man land relationship and other multivariate mixed analysis methods,this paper analyzes the changes in the number and area of urban landscape lakes,the spatiao-temporal pattern evolution characteristics and the ecological effects of changes.The main influencing factors of urban landscape lakes change are analyzed by using geographic detector combined with spatio-temporal geographic weighted regression model.The main research conclusions showed as follows:（1）The number of urban landscape lakes in the Yellow River Basin is increasing,but the scale is small,and the main types are lakes less than 10 hm~2.From 1990 to 2018,3437 urban landscape lakes were added and 806 disappeared,with a new area of64668.34 hm~2 and a disappeared area of 18526.96 hm~2.The main changes are concentrated in the middle and lower reaches.The quantity dynamic degree decreases first and then increases,and the area dynamic degree decreases first and then increases slowly.The areas with large area change intensity index are mainly concentrated in Shandong Province,and the smallest area is Yinchuan city.The area of newly added and expanded urban landscape lakes from 2000 to 2010 is not equal to that of disappeared and shrinking urban landscape lakes.The main types of changes are 10-100 hm~2 and 1000-5000 hm~2.（2）The urban landscape lakes in the Yellow River Basin are distributed from northwest to southeast,and the standard deviation ellipse center moves.The trajectory is northeast-southwest-northwest,and the average nearest neighbor index is 0.203,0.196,0.185 and 0.171 respectively.The spatial structure is concentrated,and the degree of agglomeration is continuously strengthened.The spatial density features a distribution pattern of"high in the East and low in the west",gradually forming a gathering area with Shandong Province as the main core,spreading in the form of circles to the surrounding areas,and forming a continuous density interval in the region.After 2000,the high-value area and the middle-value area have gradually broken through the"Hu Line"and extended to the northwest area of the Yellow River Basin.（3）The transformation intensity between urban landscape lakes and other land use types is farmland>impervious surface>grassland>desert>forest in the Yellow River Basin.From 1990 to 2000,the transfer in in the transformation relationship with farmland was about 3.5 times that of transfer out,which was closely related to the policy of returning farmland to lake implemented during the period.The number of cities whose urban landscape lakes change improve the value of regional ecosystem services first decreases and then increases.From 2000 to 2010,more than half of the regional urban landscape lake changes did not meet the needs of regional social and economic development,which had a negative impact on the ecosystem service function.In the three periods,the proportion of cities whose ecological risk index decreased due to urban landscape lakes in the Yellow River Basin did not exceed 50%.More than half of the cities improved the regional ecological risk,reduced the ability of the ecosystem to resist external interference and its internal self-regulation and recovery ability.（4）The spatial diversity of urban landscape lakes in the Yellow River Basin is not uniform and unique.The result of vertical effect is the product of the interaction of influencing factors.There are spatial differences in the direction and intensity of significance factors on the change of urban landscape lakes in different analysis units.Average temperature,per capita GDP and population density are the main factors affecting the change and differentiation of urban landscape lakes.Natural environment is the basic influencing factor of the construction of urban landscape lakes in the Yellow River Basin.Social economy is the key factor in the spatial distribution pattern and evolution of urban landscape lakes,which restricts the spatial extension direction of urban landscape lakes.