Abstract:

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.

Key words: ecosystem services, emergy analysis, ecological conservation area, Beijing