明确城市生态系统服务的空间分布格局，对揭示城市生态系统过程与功能，探讨城市生态系统服务的空间异质性，分析城市生态系统服务的不均衡性具有重要意义，能够为城市生态系统管理提高重要信息。本文以北京市六环内为研究区域，分析了城市植物多样性、土壤性状，尤其是土壤碳库以及重金属污染物-铅在不同城市化区域、不同土地利用类型中的空间分布，探讨了城市生态系统服务的空间分布格局。主要结论有：（1）沿着城市近郊区-过渡区-城中心的城市化梯度，城市植物总的物种丰富度并未改变，但城市绿地的人工绿化增加了外来物种的多样性；城市土壤养分（如速效磷、速效钾、有机碳）与土壤重金属-铅显著增加，土壤养分的增加主要归因于绿地施肥、空气污染物沉降、建筑材料、居住区生活废弃物，土壤重金属铅含量的增加主要归因于交通污染物排放、历史重工业活动及居住区含铅油漆。（2）不同土地利用类型中，城市居住区的植物多样性尤其是外来物种的多样性较高，而城市森林与交通绿化带的物种多样性较低；尽管行道树、居住区的土壤pH与土壤容重较高，但也同时含有更高的土壤养分与重金属污染物-铅；与交通用地以及居住区相反，城市森林的土壤养分与重金属含量均较低，但其土壤有机碳的比例显著高于其他土地利用类型。（3）城市生态系统服务与其负效应同时存在。城市植被乔木的物种多度以牺牲灌木多度、草本多度为代价；居住区更高的外来花粉致敏植物的多样性可能存在健康风险；城市化增加的土壤有机碳比不上增加的无机碳含量；城市化在增加土壤养分输入的同时，也增加了重金属污染物-铅、铜。

Understanding the spatial distribution of urban ecosystem services would contribute to analyze urban ecosystem processes and functions and provide important information for the urban ecosystem management. We studied the spatial distribution of urban ecosystem services in Beijing by investigating the variation of plant biodiversity, soil properties, soil carbon pool and lead (Pb) across the urbanization gradient and different land use types. Our major findings are:(1)The richness of total species and native species did not show significant differences from the suburban area to urban core, while the richness of exotic plants increased significantly, mainly due to introduced plants for urban greening. Both of soil nutrients (e.g. available phosphorus, available potassium, organic carbon) and soil heavy metal contents (e.g. Pb) increased. Human fertilization, air pollutant deposition, building materials and household garbage all contribute to increasing soil nutrients. Traffic pollutants, industrial activities and lead-based paints are the main causes for the relatively high soil lead level in urban area. (2) Plant diversity, in particular, the richness of exotic plants was relatively high in residential areas, but low in urban forest and road green-belts. We found soils in roadsides and residential with relatively high soil pH and bulk density. In addition, roadsides and residential areas had the highest levels of soil nutrients and heavy metals, which are found to have the lowest levels in urban forests. However, urban forests have significantly higher proportion of soil organic carbon than other land uses.（3）Urban ecosystem provides services and disservices. In urban green spaces, the abundance of trees is always negatively related with the abundance of shrub and herbs. The higher plant biodiversity, especially the richer exotic allergenic plants in residential areas could increase human health risk for respiratory disease. Although human activities tend to augment urban soil nutrient pools to maximize certain ecosystem services, they may inadvertently compromise these and other services by increasing pollution.