口袋公园在保护城市蝴蝶多样性方面的价值

Butterflies, valued for their aesthetic and ecological value, are key subjects in urban biodiversity research. Our study focused on the often-overlooked roles of pocket parks, which are micro-greenspaces and small amusement parks open to the public. Despite their limited size, pocket parks are vital in maintaining the diversity of urban butterflies. We aimed to determine 1) how many butterfly specie s live in pocket parks, 2) the limiting variables for the ability of pocket parks to provide habitats for butterflies with different urban adaptabilities; and 3) the roles pocket parks play in this process when they provide habitats for butterflies with different adaptabilities. [Method]We conducted surveys of butterflies and vegetation in urban parks and pocket parks in 2020, from July to September in Beijing, China. We also selected seven environmental variables from food resources and shelter and recorded them at the same time. These include pocket park area, canopy coverage, tourist intensity, management intensity, water body, host plants and nectar plants. The last three were binary data, the first two were continuous data and the intensity of tourist and management were ordered data. Firstly, we contrasted pocket park’s butterfly diversity and the Jaccard index of vegetation with urban parks by using the Mann-Whitney tests. Next, using hierarchical clustering, we classified butterflies from urban parks and pocket parks into urban exploiters, urban adapters, urban avoiders and pocket park exploiters, pocket park adapters, pocket park avoiders based on how well they adapted to environments, respectively. Finally, we used Logistic regression and Poisson regression to build generalised linear models for all species and each of the three groups from pocket parks separately, allowing us to investigate the differences in the effects of variables from food resources and shelters on various butterfly groups in pocket parks. Using the Akaike information criterion, we adopted the one with the lowest AIC value as the final model. [Result]We finally recorded 1104 butterflies from four families and 16 species from pocket parks, and 2748 from five families and 20 species from urban parks. The Mann-Whitney tests showed that the butterfly diversity in pocket parks was lower than in urban parks and the former’s vegetation composition was more homogenous. The hierarchical clustering analysis showed that pocket parks can provide habitats for all urban exploiters and urban adapters, and some urban avoiders. According to the results of generalised regressions, the primary restrictions differ depending on the group. Management intensity, pocket park area and nectar plants were significant variables for all species. The tourist intensity and host plants were variables that affected the presence of exploiters, but both were insignificant. Food variables (host and nectar plants) and managementintensity were the most influential variables for the adapters, with the latter being significant. However,even at the lowest level of management intensity, the probability of the presence of adapters was greater than 0.5 only when both the host and nectar plants were in a pocket park at the same time. Nectar plants, management intensity, and pocket park area influenced the presence of avoiders and area was the only significant variable. Moreover, the likelihood of all avoiders appearing in our study was not greater than 0.5, and of the three groups, only the avoiders were sensitive to the size of the pocket park. [Conclusion]These results showed that 1)pocket parks provide habitats for most of the butterfly species(more than 76% ) in Beijing, 2) the needs and adaptations of the three communities were distinct, and 3) pocket parks have roles as source and sink habitats for exploiters and adapters and as stepping stones and corridors for most butterfly species inhabiting cities. According to the results, we suggested that 1)in the process of urban planning, for butterfly biodiversity conservation, green wastelands and brownfields should be identified and pocket parks should be considered in habitat network construction, 2) in the process of pocket park management, spontaneous vegetation inside the forest should be reserved to provide more host plants and cultivate flowering plants at the edge of the forest or along the path to provide more nectar plants for butterflies and recreational environment for residents and 3) more research should be done by considering external environment impacts and comparing butterfly community characteristics across green space types.