北京市生态涵养区生态系统服务供给与流动的能值分析

近年来北京市建成区扩张迅速,对城市周边地区的生态系统服务需求上升。本文以北京市生态涵养区为例,利用能值评估方法评估该区域生态系统服务,分析各生态系统及其与城市系统之间的服务流动和依赖关系。研究结果表明：从生态系统类型上看,2012年森林生态系统服务对涵养区生态系统服务贡献最大,占到生态系统服务总能值的79.7%,其次为农田和水域生态系统,分别占总能值的19.7%和0.6%;从生态系统服务类型上看,森林生态系统的有机物生产和水源涵养是其主要的生态系统服务,分别占总能值产出的40.4%和35.8%。粮食供给是农田系统的主要能值输出,占农田生态系统能值的70%。水域提供的生态系统服务中,能值比例较高的依次为水源供给、洪水调蓄和水产品供给,分别占水域生态系统能值的35.1%、28.6%和28.2%;从能值转移矩阵分析可以看出,对城市来说,森林生物量、森林土壤水、水域地下水和农田生物量是重要的生态系统服务供给组分;系统能值动态分析结果表明,2004年到2012年森林和水域生态系统重要程度增加,农田生态系统重要程度有所减少,城市系统的角色由主动变为被动。因此,在未来的发展规划中,对森林和水域生态系统的保育应给予足够关注。

Emergy analysis of ecosystem services supply and flow in Beijing ecological conservation area

Beijing, as the political, communicational, cultural, and technological center of China, has been experiencing rapid urban expansion in recent years. This fast urbanization resulted in greater demands for ecosystem services from peri-urban ecosystems. Based on emergy analysis and using impact matrix, this study took the urban ecological conservation area (ECA) of Beijing as an example to evaluate the ecosystem services flows and the level of dependence between natural and urban systems. In terms of ecosystem types, results show that forest ecosystem contributes the most to ecosystem service provision in ECA, which represents 79.7% of total ecosystem services emergy in 2012. Meanwhile, cropland and aquatic ecosystems account for 19.7% and 0.6%, respectively. From the perspective of ecosystem services types, biomass production and water retention are the two dominative service types provided by forest ecosystem, accounting for 40.4% and 35.8% of forest ecosystem services emergy respectively. Food supply is the most significant emergy component in cropland ecosystem, which represents 70% of cropland ecosystem service emergy. Water supply, flood storage and aquatic product supply are the three most important emergy components in aquatic ecosystem, which account for 35.1%, 28.6% and 28.2% of the total aquatic emergy respectively. Results of emergy impact matrix suggest that forest biomass, soil water, groundwater and cropland biomass are the four vital providers of ecosystem services to urban system. At the temporal scale, results demonstrated that forest and aquatic ecosystems played more and more significant roles in water retention and water supply while cropland ecosystems became less and less important in food supply from 2004 to 2012. Urban system also transformed from a positive influencing to a passive receiving factor of ecosystem services in this period. Accordingly, more attention should be paid to conservation of forest and aquatic ecosystems in future urban planning in order to achieve better ecosystem service provision.