The association between plant diversity and perceived emotions for visitors in urban forests: A pilot study across 49 parks in China

Urbanization introduces uncertainties to the biodiversity of plant communities. The perception of biodiversity can be associated with positive mental health and well-being, but direct evidence is still insufficient. In this study, we collected data about plant biodiversity assessments from studies on urban forests in the literature of China's national knowledge infrastructure. Records of the species amount, Shannon index, and Simpson index were extracted from 49 urban forest parks in 13 cities across mainland China from 2018 to 2021. A total of 1938 facial photos were obtained from microblogs with check-in locations at these parks in the Sina Microblog in 2020. Happy, sad, and neutral emotions and positive response index (PRI; happy minus sad) were rated and mapped for spatial distributions. The amount of species was distributed as a heterogeneous pattern for all plant types, and biodiversity was higher in the northern regions (e.g., similar to 55% in Qingdao and over 50% in Taiyuan) than in southern cities along the Yangtze River (e.g., similar to 35% in Huaihua and Changsha). Trees did not account for the association of biodiversity with emotional expressions. Smiles were elicited mostly in parks with more diverse shrubs (Shannon index: R=0.4335; P = 0.0029) and herbs (R=0.6162; P = 0.0008). Females showed more smiles than males (47% vs. 32%, respectively; F=39.15, P < 0.0001), and happy emotions tended to be higher in older visitors (senior vs. younger: 58% vs. 43%, respectively; F=2.72, P = 0.0280). Overall, we recommend visiting parks in northern cities of China for the benefit of evoking positive emotions through experiencing abundant undergrowth species. Female visitors would benefit more than males in the promotion of mental well-being by perceiving diverse shrubs and herbs in urban forest parks.