Under the background of global urbanization, optimization of urban morphological pattern is one of important issues for the sustainable urban form. The vegetation biomass in the city is a parameter standing for multiple environmental targets, including carbon sequestration, climate regulation, pollution reduction etc. For the process of urban expanding to encroach on vegetation, the lost vegetation biomass quantitatively connects with the urban morphological pattern. This paper established the quantitative relationship between six selected urban form indicators and biomass loss caused by urban expansion (TBLI), with the aim of providing a specific optimization to the urban space configuration. The results indicate that six urban form indicators in fifty cities had their own characteristics, in which the Richardson compactness (0.452~0.402), density gradient (0.034~0.326) and Gini coefficient (0.527~0.995) show that the compactness of city center in large cities were generally lower than those of small or medium-sized cities. TBLI in Yangtze River Delta had reached 2.97 Tg during the study period, in which biomass loss in small or medium-sized cities were less than those of large cities, for example, Shanghai (0.529 Tg). TBLI was significantly related to urban form indicators, OLS model (TBLI=0.00051 [Urban land increment]-0.09127 [Richardson compactness]-0.11352 [density gradient]-0.05313 [Gini coefficient]+0.118) represented the average estimation of biomass loss in the whole region. However, topographic conditions and land cover types were the main causes of spatial non-stationarity. Through urban form optimization, such as enhancing circularity of external contour of Nanjing-Zhenjiang-Yangzhou urban agglomeration, improving the compactness of elements in Taizhou urban agglomeration, and breaking the balance distribution pattern in southeast part of Zhejiang Province, biomass loss could be reduced significantly. GWR model was superior to the OLS model on fitting accuracy and visualization of modeling parameters.%在全球性城市扩张背景下,形态格局优化是城市可持续性研究的重要内容.植被生物量作为综合表征多环境目标的参量,在城市扩张的土地覆被变化过程中,与城市形态格局产生了内在联系,可作为城市形态环境性能的评判依据.基于长江三角洲50个城市样本的城市扩张和植被生物量损失数据,研究城市扩张下植被生物量损失(TBLI)与城市形态指数的定量关系,旨在为城市空间布局提供具体的优化手段.研究结果表明:50个城市的各类形态指标各具差异,其中Richardson紧凑度(0.452~0.402)、密度梯度(0.034~0.326)和Gini系数(0.527~0.995)的估算结果显示,总体上长三角城市用地呈极化分布,大城市的中心形态紧凑性普遍低于中小城市;研究期内由城市扩张造成的长三角生物量损失高达2.97 Tg,上海的损失量(0.529 Tg)最大,中小城市的生物量损失较小;TBLI与各类形态指标显著相关,由OLS分析构建的模型:TBLI=0.00051[城市用地增量]-0.09127[Richardson紧凑度]-0.11352[密度梯度]-0.05313[Gini系数]+0.118,可估算长三角生物量损失的平均概况;通过地理加权法分析地形条件及土地覆被类型等所造成的结果的空间非平稳性,表明可着重增强宁镇扬城市群的外部轮廓形态的趋圆紧凑性,提高台州城市群内部要素密度分布的紧凑性,以及增加宁波、慈溪等浙东南沿海区域内建设用地的集聚性,来显著减少生物量损失.在城市形态与植被生物量的动态响应机制方面值得作进一步研究.
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