近二十年来上海不同城市空间尺度绿地的生态效益

基于CITYgreen模型,通过对1987、2000、2004和2008年4a的TM影像分析,从上海城市空间大尺度(上海市外环内整体)、中尺度(上海市外环内各行政区)和小尺度(上海市外环内各镇及街道)计算绿地年固碳和空气污染物去除两项生态效益,其中大尺度绿地的生态效益为:1987年为16722.58万元,2000年为8546.36万元,2004年为8161.48万元,2008年为968.47万元。继而利用基础统计学以及ArcGIS地统计分析扩展模块对生态效益进行分析,得出结论:(1)大尺度上分析,1987年至2008年,由于受到城市建设用地拓展的影响,城市绿地生态效益总体上呈下降趋势;(2)中尺度上分析,不同行政区绿地生态效益的浮动范围与变化趋势均不相同,中心城区外围的浦东区、宝山区、普陀区等一直处于较高水平且变动幅度较大,而中心城区一直处于较低状态;(3)小尺度上分析,基于克里格插值的曲面拟合分析表明中心城区部分区域出现回升。旨在通过模型拟合分析,完善上海市绿地生态效益研究,并为特大型城市绿地规划建设提供科学依据。

Ecological effect of green space of Shanghai in different spatial scales in past 20 years

Green space plays a great role in improving environment, maintaining the balance of ecosystem and promoting low-carbon city construction. So the study on ecological effect of green space becomes significant to green space planning & construction and ecosystem service enhancement. Models based on ArcGIS and ArcVIEW platforms like CITYgreen and i-tree have been widely applied in ecological effect study, especially CITYgreen model application in Shenyang, built-up area of Beijing, Beijing Olympic park, Nanjing, Shanghai Outer Ring Green Belt, Hangzhou and Shenzhen. Based on CITYgreen Model and the TM image analysis of 1987, 2000, 2004 and 2008, in three spatial scales including large scale (the whole area within Outer Ring Rd. of Shanghai), middle scale (districts within Outer Ring Rd. of Shanghai) and small scale (towns & sub-districts within Outer Ring Rd. of Shanghai), the annual carbon storage and air pollution removal ecological effect were calculated, with the large scale results: 167.2 million yuan in 1987, 85.5 million yuan in 2000, 81.6 million yuan in 2004 and 9.7 million yuan in 2008. Then the comparative analysis was done with basic statistics and the Geostatistical Analyst of ArcGIS. The results showed that: (1) In large scale, from 1987 to 2008, overall ecological benefit declined because of the encroachment of urban construction. Although many measures to green space construction have been taken in Shanghai City, the situation within the Outer Ring Rd. still calls for much more efforts; (2) In middle scale, two parts of analysis were done including all the 14 districts and the central 6 districts and the results showed that ecological effect of different districts have different range and variation trend; ecological effect of the outer districts keeps on higher level but changes heavily and the central were always in a low state. Although some measures about building green space have been brought up, the amount of the study area is still decreasing. In addition, most of the increased green space focuses on landscape and recreation function, which leads to the loss of ecological benefit; (3) In small scale, based on Kriging, with surface fitting analysis, the central area had a brief rally during the overall decline trend, especially in the period of 2000 to 2004, due to the green-built measures conducted by Shanghai Municipal Government. Besides, stain chart shows the ecological effect change of every towns and sub-districts, which complements the result of large and middle scale result. There exist differences and connection among study in three spatial scales and from three scales, results of different aspects were presented, which means a lot to the detailed green space planning and construction. Through all the data analysis, this study on ecological effect of green space in Shanghai will get perfection and some scientific basis which will be provided as well for green space planning of large cities like Shanghai. Of course, there are still much more scientific issues to be solved, like the accurate carbon storage of urban green space and the relative questions about carbon sink forest in urban area have become the hottest issue in this field. The results of this study can be the stepping stone of scientific researches in future.