PS 48-244 - Tree and shrub species composition is unchanged from urban forest edge to interior

Abstract: The majority of temperate forest in the eastern U.S. exists as a patchwork of small, isolated, urban forests, often with a history of deforestation followed by regrowth under surrounding urbanization. Many of these forests are bound by roads or residential development, creating abrupt forest edges. Previous research has suggested that proximity to a forest edge alters environmental conditions and the structure and composition of the plant community. Light availability, temperature, and shrub abundance have all been shown to increase from the forest interior to the forest edge. Because urban forests exist in highly populated areas, humans rely on them to provide physical and mental health benefits. Additionally, we increasingly rely on the carbon (C) storage potential of forests as nature-based solutions for climate change, but if the structure of a forest declines it may not be able to provide these services. In 2020 and 2021, our research team inventoried all tree species within 36 forests across 5 cities. Within each forest we sampled plots spanning a gradient from the forest interior to the forest edge.

Here, I examine tree and shrub species composition changes from the forest interior to the forest edge in urban forests using NMDS analysis. Tree species composition from forests in Springfield MA, Philadelphia PA, Newark DE, and Baltimore MD, revealed there are no pronounced associations between dominant tree species and proximity to the forest edge. Tree species composition is similar from the forest edge to interior. Overall, shrub species composition is similar from the forest edge to interior, with the exception of Rosa multiflora, which is weakly associated with proximity to the forest edge. These findings indicate that other site characteristics; history, location, or canopy openness, exert a greater influence on the plant community than proximity to the forest edge. Future research should investigate whether tree growth in urban forests shows a relationship with distance to the forest edge.