Study On Ecological Effects Of Urban Green Space In Shanghai Based On GSI Model

Urban green space is an important part of the urban ecosystem and its ecological effects has played an important role on the quality of urban environment. Both domestic and foreign studies have shown that urban green structural features influence their ecological effects a lot. Based on the the Science and Technology Support Program, titled on "Acquisition and evaluation of standardized information of urban green space ", quantitative models urban green space structure, the quantitative relationships between eco-effects and urban greenland structure have been studied in this paper.According to records of ecological investigation in the field,we take the green space in Shanghai as case study. Various types of eco-effects are monitored. Greenland structure index (GSI) model was established by factor analysis. The quantitative relationship between the GSI and its eco-effects was studied. Visualization information system was established as wellThe results show that:(1) Based on the data surveyed in the Shanghai area, Greenland structure Index (GSI) model was established for quantitative evaluation of the structure of green space.The model could reflect the ecological stuctural characteristics of urban green space.Function model of the greenland structure index (GSI) consists two principal components F1and F2. The two principal components F1, F2are two separate factor variables;F1is a tree structure factor variable, mainly reflecting the information of four tree structure factor including average DBH, average tree height, average crown diameter, average LAI; F2is a an overall greenland structure factor variable, mainly reflecting the information of three greenland structure factor including canopy cover, shrub and grass cover and trees number. F1weights0.64,F2weights0.36. GSI function model is as GSI=0.64F1+0.36F2. The function of GSI model can reflect78%of the amount of information of the original data.(2) Cluster analysis is conducted based on the GSI values of72sanples.GSI value of sample field in Shanghai could be divided into six categories, from low to high. I, â…¡,â…¢,â…£ and â…¤ and â…¥. According to the Classification criteria,The main three classes of GSI in Shanghai are â… , â…¢, â…£. Green space with GSI in class I are mainly grassland; Green space with GSI in the class III are maily Tree-Grass, Shrub-Grass or thin Tree-Shrub-Grass type with canopy density of35%-between50%and tree planting is more dispersed or crowns are smaller; Green space with GSI in class IV are mostly composite Tree-Shrub-Grass type with canopy density of50%-80%and large number of trees; GSI could reflect greenland structure characters.(3) Based on the Normalized difference vegetation index (NDVI) from Landsat TM/ETM remote sensing data, statistical model of NDVI and GSI is established:y=-1.511x2+1.9023x, R2=0.6721(x-NDVI; y-GSI); Based on the relationship between GSI and ecological effects, the general distribution of green ecological effects could be accessed and it provides new research idea for the access of spacial eco-effects in large scale. However, due to the lower image resolution of remote sensing image, the accuracy of green ecological effects in spacial distribution is not high, it is vital to improve resolution of remote sensing image in our further study.(4) Based on GSI and ecological effects data, Eco-effects including micro-climate regulation,absorbing carbon dioxide, deposition of dust (PM10), resulting in air negative ions was studied from two aspects including seasonal variation and sample variation. The results show that:1) Regulation of micro-climate of green space in different seasons are more easily subject to the seasonal change than GSI change; Regression relationships exists between eco-effects of regulating micro climate and GSI in summer are as follows:y=12.759x2+3.1208x+1.8811, R2=0.7667(x is GSI, y is the green cooling rate); y=2.174e28604x, R2=0.7415(x is GSI, y is the rate of green humidifiers).2) The ability to decrease carbon dioxide in the air get a better play when GSI is in the0.4-0.5range, the background value of carbon dioxide concentration is at550ppm to570ppm.3) Effects of depositon of PM10of green space in different seasons are more easily subject to the seasonal change than GSI change. Regression relationships exists between eco-effects of depositon of PM10and GSI in summer are as follows:y=10.6441n(x)+5.3629, R2=0.6322.(x is LAI, y is the rate of PM10depositon)4) Resulting negative air ion of the green in differernt seasons is more subject to GSI change than season change. Regression relationships exists between the effects of increasing negative air ions and GSI in summer are as follows:;y=0.2825e0.0133x, R2=0.8979(x is GSI, y is the rate of resulting negative air ions).Besides,The concentrations of negative air ions in a fixed urban plant community are affected by the microclimate. It is negatively correlated with temperature and positive correlated with relative humidity, there is no significant relations between PM10and negative air ions.negative air ions have a V-type or U-type nonlinear correlation with light intensity..(5) Based on the relationships of GSI model, GSI and ecological effects, the visual information system of structure and ecological effects database for Shanghai green space were established in this study. The visual information system could achieve a visual query and editing of original green information and prediction of ecological effects of space based on the GSI. The visual information system could provide management support for the planning of urban green space in Shanghai.