Effect of spatial heterogeneity of plant communities on air PM10 and PM2.5 in an urban forest park in Wuhan, China

Abstract

Understanding the associations between plant community characteristics and their effects on ambient particulate matter (PM) is a central theme of urban forest park management and development so as to maximise ecological services. The ambient PM concentrations and spatial distribution of plant communities in urban forest parks are not random, but show strong spatial patterns. We selected Ma'’anshan Mountain Forest Park in Wuhan, China, as an example of a typical park. The monitoring network consisted of 44 different plant communities at various locations that were monitored in December, April, July and October. The effects of the spatial heterogeneity of plant communities on ambient PM10 and PM2.5 were analysed using a spatial model to investigate the relationships between plant communities and levels of ambient PM. The results showed that differences in levels of ambient PM among plant communities resulted from both their composition and location. However, when spatial patterns were corrected, large seasonal variations in PM patterns were revealed due to seasonal differences in the characteristics of plants communities and pollution emissions. Significantly lower ambient PM concentrations were recorded in small-scale plant communities that were mainly distributed in the mountain areas and comprised of Pinus, Platycladus, Cunninghamia, Taxodium, Metasequoia, Quercus, Platycarya, and Cinnamomum. Correlation results revealed that six factors — diameter at breast height (DBH), leaf area index (LAI), canopy area (CA), slope (S), distance from pollution source (DPO) and distance from edge of park (DP) — had significant effects on ambient PM reduction. We found that ambient PM decline was primarily attributed to large DBH and community DPO. The effect of small-scale plant communities on ambient PM decline was the most significant in December, followed by October, April, and July. These plant community attributes are the basis of forest ecological services, and our findings indicate that the regulation of plant communities could improve urban forest services by increasing the efficiency of ambient PM concentration reduction.