A Study On Ecological Benefits Of Green Spaces In Downtown Shanghai Based On CITYgreen Model

At present, China's urbanization process has been accelerated. The rapid development of city brings modern civilization for human, promote social, economic and cultural development but it also bring many urban problems. A bulge in urban population increase the pressure of city ecosystem, the development of industry bring with environmental pollution, seriously affect physical and mental the health of human. However, green space can improve the ecological environment of city, promote coordination between human and nature, and meet the requirements of sustainable development. The majority of ecological benefits of green space has been studied, but the research is in the qualitative phase, and quantitative assessment of accurate and effective is relatively less. Therefore, how to accurately quantify the ecological benefits of green space has become an important issue we face.This study is based on CITYgreen model, assessing the ecological benefits of green spaces in Downtown Shanghai from structure of green space, different region and green space type. Based on the assessment of the CITYgreen model, and use AHP to establish green space ecological benefits quality evaluation index system, assess the quality of the green space ecological benefits in Downtown Shanghai. The results and conclusions are as follow:(1) Relationship between structure of green space and ecological benefits:canopy closure and carbon density, air pollution removal, stormwater runoff reduction were significant positive correlation; the average diameter at breast height and carbon density was significant positive negative correlation; the average diameter at breast height and carbon sequestration rate was significant negative correlation; tree height was not significant correlation with carbon density, carbon sequestration rate, air pollution removal and stormwater runoff reduction; the number of trees per hectare was not significant correlation with carbon density, carbon sequestration rate, air pollution removal and stormwater runoff reduction. The ecological benefits values of green space of multi-storied structure was higher than single structure, but the ecological benefits of the difference was not significant; the value of the ecological benefits excluded carbon sequestration rate of mingled forest was higher than pure.(2) Assessment of matter amount:carbon sequestration rate, air pollution removal, stormwater runoff reduction and carbon storage were 8.70×102 t·a-1,66.94 t·a-1,4.47×104m3·a-1 and 4.02×104t respectively in Downtown Shanghai in 2010. Assessment of value amount:the ecological value of carbon sequestration, air purification, stormwater runoff reduction, biodiversity conservation and carbon storage were (?)1048 thousand, (?) 905 thousand, (?) 273 thousand, (?) 12417 thousand and (?) 48 222 thousand respectively in Downtown Shanghai in 2010; the ecological benefits amounted to (?) 14 643 thousand; the average value of ecological benefits was (?) 14 500 hm-2·a-1; the growth rate of ecological benefits was (?) 1063.3 hm-2·a-1(3) The assessment of matter and economic value of ecological benefits in different area can be concluded, in descending order were Yangpu, Xuhui, Changning, Putuo, Zhabei, Hongkou, Luwan, Huangpu and Jingan. The assessment of matter and economic value of ecological benefits of different green space type in descending order were comprehensive park, topic park, other green space, community park, roadside green space, zonal park.(4) Based on the evaluation results of the CITYgreen model establish green-land ecological benefits quality evaluation index system:the first layer is the target layer, that is the green space ecological benefits quality evaluation indicator; the second layer is the rule layer, including environmental indicators, vegetation indicators and economic indicators, a total of three indicators; the third layer is the index level, that is each of the evaluation factors to the expression of specific targets, a total of 10 indicators.(5) Green space ecological benefits quality assessment composite index results were as follows:the rating scale of Yangpu, Jingan and Putuo was I class; the rating scale of Hongkou, Zhabei and Xuhui wasⅡclass; the rating scale of Changning and Luwan wasⅢclass; the rating scale of Huangpu was IV class. Composite index of different green space type were as follows:the rating scale of other green space was I class; roadside green space wasⅡclass; community park, comprehensive park, topic park and zonal park wereⅢclass.