环境正义视阈下城市公园绿地时空可达性及其影响因素

从环境正义视阈出发，重点关注选择步行和私家车出行的居民群体，采用高斯两步移动搜索（2SFCA）模型和基尼系数测度2000-2018年武汉市中心城区公园绿地可达性和公平性的时空差异，并运用梯度提升决策树（GBDT）模型进一步探析交通因素、用地因素和社会经济因素对公园绿地可达性的非线性影响及其阈值效应，以期为公平导向下的城市绿地规划提供相关参考。结果表明：（1）研究时段内公园绿地供给与需求均呈现较快的增长，居民出行成本在逐渐降低；（2）居民选择两种交通方式出行的公园绿地可达性高值区域均呈现扩大趋势，主要分布在长江两岸、湖泊和大型风景区周围，但是不同时期步行方式可达性低值区域均多于车行；同时，基尼系数显示研究时段内两种交通出行的居民享受公园绿地服务的机会均不公平，且步行可达不公平程度远大于车行；（3）用地结构和社会经济因素对不同时期公园绿地服务可达性存在协同性影响，而交通因素是不同交通方式出行可达性存在差异的主要原因；（4）非线性关系图显示关键变量的阈值效应能够为城市绿地精细化规划与管理提供量化参考。

Spatial and temporal accessibility of urban green space and its influencing factors in Wuhan from the perspective of environmental justice

From the perspective of environmental justice, this study focuses on residents who choose to walk or travel by private car, and uses Gaussian-based two-step floating catchment area (2SFCA) model and Gini coefficient to measure the spatio-temporal disparity of the accessibility and equity of PGS in Wuhan''s central urban area from 2000 to 2018. The non-linear influence and threshold effect of traffic factors, land use factors and socio economic factors on the accessibility of PGS are further analyzed by using the Gradient Boosted Decision Tree (GBDT) model, which is aimed at providing relevant reference for urban green space planning under the guidance of equity. The results showed that:(1) The supply and demand of PGS increased rapidly and the travel cost of residents decreased gradually during the study period; (2) The areas with high accessibility of PGS in two modes were expanded, and it was mainly distributed around the banks of the Yangtze River, lakes and large scenic areas, but the areas with low accessibility by walking were more than those of driving in different periods. Meantime, the Gini coefficient showed that residents enjoyed inequity opportunities to park green space services by walking and driving, and the degree of inequity by walking was much greater than that of driving; (3) Land use structure and socio economic factors had synergistic effects on the accessibility of PGS in different periods, and traffic factors were the main reason for the difference in accessibility between different modes; (4) The non-linear diagram showed that the threshold effect of key variables could provide a quantitative reference for the refined planning and management of urban green space.