Abstract: The key step in the construction of Chinese nature reserves system is its integration and optimization. Ecological value is an important basis for the integration and optimization ofnature reserves and one of the most important indicators for the analysis of protection vacancies. Here, we used the shadow project method and carbon tax method to calculate four types of ecological values of ecosystems in Beijing in 2019, including water conservation, soil conservation, windbreak and sand fixation, and carbon fixation. We further analyzed the ecological value distribution of nature reserves. Subsequently, the protection vacancy analysis was carried out based on the ecological value. The results showed that soil conservation had the highest ecological value (10665 yuan·hm^-2) in Beijing, followed by windbreak and sand fixation (8417 yuan·hm^-2). The value of water conservation was negative (-21702 yuan·hm^-2), indicating that water conservation was under deficit in Beijing. Water conservation of the nature reserve had the highest value (100972 yuan·hm^-2), followed by soil conservation (17738 yuan·hm^-2), windbreak and sand fixation (8422 yuan·hm^-2), and carbon fixation (1051 yuan·hm^-2). The average ecological values of water conservation and soil conservation functions of national nature reserves were higher than that of the other types of nature reserves, while the average value of the four types of ecosystem services of geoparks was generally low. Analysis of protection vacancies based on ecological value manifested that areas with high ecological value were located in the mountainous areas of western and northern Beijing, and the area of protection vacancies adjacent to the boundary of the existing protected area was 1249.82 km². Our results showed that we can reasonably analyze the protection vacancies of the nature reserves in Beijing based on the valuation results of ecosystem services.

Key words: Beijing, nature reserve, ecosystem services, protection vacancy.