| Urban green space is an indispensable part of urban development and public life.It provides a comfortable rest and living environment for the citizens,and has a certain adjustment and coordination role to the urban ecological environment and the allocation of resources.With the adjustment of urban strategic positioning,functional expansion and the layout and adjustment of public infrastructure,the structure and scope of urban green space layout presents a certain evolution law.It is beneficial to explore the ecological environment effect of green space and provide the decision-making basis for the government departments to plan the urban spatial structure and optimize the layout of the urban green space.The internal structure of urban green space is not"balanced"to the ecological environment of the city,but shows obvious differences and structural characteristics.In order to explore the temporal and spatial evolution law of green space and its composition structure,the relationship and mechanism of each structure and urban ecological environment effect are discussed in depth.In this paper,the Landsat satellite data and social and economic statistics of 2000-2016 years in the main city of Chongqing are adopted,and the technology of GIS space analysis and remote sensing quantitative processing technology are combined.And model analysis technology,through the construction of a number of quantitative analysis models,the research area of urban green space information extraction methods,spatial and temporal evolution characteristics and the urban ecological environmental effects of the correlation and interaction and mechanism of three aspects of research.The main research process and conclusions are as follows:(1)Based on the high time resolution(1 years)and medium spatial resolution(30 m)data of the long time series of Landsat TM/ETM+,combined with the spectral information of the ground objects and the phenological information of a complete growing season(5-9 months)of the cultivated land in the study area,the surface coverage of the main urban area is covered by the quantitative processing method and the model construction method.Classify and extract the green spatial information in the research area.The results showed that:(1)the study area was divided into 6 categories:building,water body,woodland,grassland,shrub and cultivated land.The surface cover classification image of the main urban area for 2000-2016 years was obtained.The average value of the total classification accuracy reached 92.24%and the average value of Kappa coefficient reached 0.91.The average classification accuracy of water bodies is the highest,reaching 100%,followed by buildings and woodlands,which are 94.67%and 93.03%respectively.The classification accuracy of grassland,shrub and cultivated land is slightly lower,87.38%,88.5%and 89.88%,respectively.(2)compared with the traditional single phase spectral classification method,using the spectral information of the multi temporal remote sensing image and combining the phenological information of the ground objects to divide the objects,the target objects can be more accurately extracted and the classification effect is better.This method is the innovation of classification technology,and provides data support and theoretical foundation for the analysis of spatio-temporal pattern of urban green space.(2)According to the green space information extracted in the first part,the area and proportion of green space and composition in the research area of 2000-2016 are calculated.The spatial and temporal pattern evolution of urban green space in the study area is analyzed and evaluated by quantitative analysis method,and the dynamic change speed of green space is studied by introducing the dynamic index of land use.This paper analyzes the evolution characteristics of green space from two dimensions of time and space.The results show that:on the time dimension,(1)The total green space area of the research area is significantly reduced by the end of 2016,reducing the total amount to 438.66km~2,of which 2000-2004 years present a rapid decline trend,and after a short recovery in 2008-2009 years,it continues to fall;(2)The internal composition of the green space:the water,the forest land,grassland,shrub and cultivated land have different trends,and the dynamic changes are different.Except for the significant reduction of cultivated land area,the other components are obviously increasing.The growth of woodland is the most prominent,the total growth of 16 years is 421.64km~2,and the growth of grassland and shrubs is relatively slow.In terms of spatial dimensions,(1)The area of green space in the study area has a slight increase except the Beibei area,and the other 8 areas show different degrees of downward trend.(2)The growth trend of woodland,shrub land,grassland and water body in the study area showed a growing trend,and the growth of each region was different,the change of water body and woodland tended to be balanced,the growth trend was relatively gentle and no obvious fluctuation,and the most significant region of the water body was the south bank area,up to 87.49%,the change of grassland.Mainly in the western part of the study area,shrubs are mainly distributed in the northeastern part of China.Their growth characteristics are mainly based on the mature old urban area.(3)The cultivated land in the nine district of the main city shows a rapid reduction trend,of which,the region with prominent change is the northeast to the southwest of the study area,and the most significant in the middle of the central Jiangbei area.On the whole,the comprehensive dynamic change speed of green space is negative,the single dynamic degree of the changes of shrub,grassland and woodland is similar,the intensity of the change is similar,the single dynamic degree of the water body is the largest,reaching 4.08%.(3)According to the classified extraction information of green space in the research area,combined with the statistical data of the green space ecological environment effect,the GRA model method was used to evaluate and analyze the relationship between the area and the ecological environment effect of the existing green space and the structure of the research area and the relationship and mechanism.Based on the statistical data of the area and related indexes of green space,first of all,it follows the rationality and scientific principle to select the cooling effect of green space,the effect of humidification(PM2.5,PM10),the effect of noise reduction and the effect of the harmful gas(SO2,NO2),and then the corresponding statistical data are used for the index.Then we quantify the value and build the grey relational model(GRA model)based on the2000-2016 years'green space area and index quantitative statistical data.Finally,combined with the social and economic development in the main urban area of Chongqing,the correlation between green space and its eco-environmental effects is quantitatively analyzed.The results show that:(1)On the whole,the area of green space in the study area is highly correlated with the ecological environment effect of the city,and its correlation degree from strong to weak is in turn:humidification effect,noise reduction effect,cooling effect,dust effect,harmful gas absorption effect.The action and the absorption of harmful gases in the environment are not obvious.(2)The relationship between the area of the 5 components of the green space and the ecological environment effect is different,that is,the ecological environment effect of the city is different.Among them,the ecological environmental effects of cultivated land,shrub and woodland tend to the same level,the ecological environment effect of woodland has obvious advantages,the ecological environment effect of water body is the weakest,mainly due to the dust effect on the environment and the absorption of gas in the atmosphere is very weak.(3)The ecological environmental effects of different components of green space are different,respectively:the effects of environmental cooling,humidification and noise reduction are the same,from strong to weak in turn:Woodland>shrubs>grassland>arable land>water;the effect of dusty to urban environment is from strong to weak in turn:Woodland>shrubs>arable land>grassland>water;The absorptive capacity of harmful substances in the atmosphere from strong to weak is:Woodland>cultivated land>grassland>shrub>water body.Based on the research results in this paper,we can provide a new direction for the government to plan and layout urban green space rationally.Through scientific and rational layout of urban green space,the ecological environment effect of urban green space is effectively played,and the rationality of urban land use and planning is improved.The government provides new ideas for the construction of ecological civilization and provides a new model for the construction of urban ecological civilization for other mountainous cities. |
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