Distribution pattern of allergenic plants in the Beijing metropolitan region

Urbanization has significantly affected the composition and distribution pattern of plant species within and around cities. Plants with airborne pollens can cause seasonal allergic symptoms that are intensified by increasing air pollution and temperature. In urban landscapes, the reduced native biodiversity, increased exotic biodiversity, and species homogenization may all affect the abundance and distribution of allergenic plants. We investigated the plants with airborne pollens in the Beijing metropolitan region to determine the distribution pattern of allergenic plants as influenced by urbanization. Our results show that native allergenic plants dominated the urban area in the region. The species richness of allergenic plants, particularly the exotic plants with airborne pollens, significantly differed between land use types. The higher the plant diversity in the urban area, the higher the frequency of allergenic plant occurrence. Despite the homogenization of the allergenic plant communities, their characteristic species were still present across the metropolitan region. The flowering allergenic plants also differed between the different land use types. We suggest that some common allergenic plants should be avoided by urban planners, especially those that are exotic to the region. Humans susceptible to pollinosis should stay away from places that are concentrated with allergenic plants, and be aware of the flowering phenology of allergenic plants.