北京城市土地复合生态服务功效演变特征

城市的发展依赖于土地复合生态系统提供各项的生态服务功能,其产出是生态服务功效,可分为正向和负向的服务功效。快速的城市化导致的土地利用变化影响了土地的生态服务功效。在GIS平台的支持下,基于遥感影像和城市社会经济发展数据,以特大城市北京为案例城市,建立了基于正向和负向生态功效的空间指标体系,采用划分单元空间网格评价方法,评估了上一版城市总体规划实施以来土地复合生态服务功效的变化特征。研究表明由于城市化的快速发展影响了土地的复合生态功效,2003—2011年城市土地复合生态功效评价结果显示,土地的生态服务负功效在增长,而正功效在不断减少,2003年土地正负服务功效空间分别为57.7%和42.3%,2011年则分别为51.3%和48.7%。2003年的生态服务负功效空间以中心城为核心,成放射状向新城辐射;而2011年生态服务负功效空间以中心城为核心向外呈饼状蔓延;外延式的城市发展空间发展模式是导致负功效增长的主要因素。为建设良好的城市生态环境,需要在未来的城市规划和管理中,重视非建设用地的生态功能管理,引导外部生态空间渗入城市,强化土地生态服务功能;同时优化城乡结合部的用地结构,保育郊区的生态环境。

Characteristics of complex eco-service efficiency changes of urban land use in Beijing,China

Land is a complex ecosystem that provides various ecosystem service functions that are necessary and important for the development of sustainable cities. For rapid urbanization and industrialization, considerable areas of eco-service land have been utilized for urban construction, resulting in serious ecological and environmental issues, such as deteriorated urban heat islands, soil erosion, air and water pollution, and decreased biodiversity, which seriously challenge the sustainable development capacity. The output of natural eco-service function is eco-efficiency, and it can be divided into positive and negative eco-services; positive eco-services could create the basis of harmony and a comfortable environment; however, negative eco-services could impede sustainable development. Urban land use and cover change are often responsible for increasing negative eco-services. To understand the process of how eco-service efficiency changes with the implementation of city master plans, this paper took Beijing as a case study based on GIS and RS technology, with the support of socioeconomic data, methods grid analyses, and complex ecological assessments, and established spatial indexes for a complex eco-efficiency assessment from both positive and negative aspects. The results showed that during the period from 2003 to 2011, when the last city master plan was being implemented, the negative eco-service efficiency of the urban land increased from 42.3% to 48.7%, and correspondingly, the positive eco-service efficiency decreased from 57.7% to 51.3%. In the last eight years, the center of Beijing City continued expanding outwards at the expense of eco-service lands, resulting in increasing negative eco-service efficiency. To create a livable and sustainable city, it was suggested that the Department of City Planning and Management should develop a strategic plan to effectively manage the city development, especially, to clearly determine the urban spatial structure. Furthermore, it is essential to strengthen the complex eco-service efficiency of the land by optimizing land use structure in urban and rural areas, and efficiently conserve the rural natural environment.