Roads limit of seed dispersal and seedling recruitment of Quercus chenii in an urban hillside forest

Abstract

Paved roads in urban forests cause forest fragmentation and thus reduce animal populations, threaten dispersal and recruitment of animal-dispersed plants. Here, we tracked animal-mediated seed dispersal of Quercus chenii in the urban forest centre and near roadsides to test the effect of paved roads on seed dispersal and recruitment. We conducted experiments in a forest patch in urban areas of Wuhan, China. The forest was dominated by the focal tree species and separated by paved roads. Only two potential seed dispersal animals, one rodent (Niviventer confucianus) and one jay (Garrulus glandarius) were observed in this stand. Seeds were removed farther but not as fast in the forest centre compared to roadsides, while no differences of seed fate, dispersal direction, and seedling establishment were detected between the forest centre and roadsides, indicating the thick vegetation along roadsides provided feeding shelters for small animals. However, when compared with primary forests containing more seed dispersers, seed removal rate in this urban forest fragment was much slower in both forest centre and roadside. Furthermore, due to road barriers, seeds were seldom moved across the paved road and remained in the fragmented stand, reflecting a limited function of seed dispersers. These results suggested paved roads isolated forests into small “islands” and weakened the ecological function of seed dispersers by impeding long distance seed dispersal. Reintroducing dispersers and building wildlife corridors would be impactful ways to restore urban forest patches.