PS 11-155 - Analyzing the efficacy of native overstory tree replantings following Chinese privet (Ligustrum sinense) removal in the Southeastern US: Recommendations for urban forest restoration practices

Abstract: Chinese privet (Ligustrum sinense) is one of the most common invaders of Southeastern floodplain forests and therefore subject to significant removal as a part of forest restoration efforts, especially in the metro Atlanta area forests. Within Atlanta, the consistent removal and native tree replanting efforts by volunteer groups provide an opportunity to study the efficacy of ongoing Chinese privet removal and replanting methods in producing desirable future forest conditions. While many studies have established the biological characteristics that increase privet invasion success, the ecological concerns of privet-dominated floodplains, and the most effective mechanisms for removal, there is limited research focusing on the long-term effects of privet removal on forest community compositions, the value of native replantings, or the interactions of privet within urban forests specifically. Thus, the goals of this study were to assess how Chinese privet removal and native overstory sapling replanting affects plant cover, species richness and biodiversity of different spatial layers of Southeastern urban floodplain forests (herbaceous, shrub, understory, canopy), specifically regarding privet regrowth and the presence of secondary invaders. To address these questions, I surveyed the herbaceous, understory, and canopy cover of eight paired plots in Morningside Nature Preserve and Atlanta Memorial Park within which Trees Atlanta conducted volunteer removal projects through the 2017, 2018, 2020, and 2021 seasons. One of each of the plot pairs was replanted with native overstory tree saplings in the following year. We found preliminary evidence that native overstory sapling replantings are not correlated with increased native herbaceous plant cover and native tree seedling establishment. Further, while Chinese privet was not found to re-dominate shrub/understory cover, there was no significant difference between the non-replanted and replanted plots in regards to Chinese privet cover. Instead, invasive groundcover species have been found to have reclaimed much of the area once inhabited by privet. In conclusion, these initial results can begin to advise urban forest restoration efforts by establishing a need for alternate replanting strategies and continual maintenance of areas that have undergone removal. Additionally, our preliminary findings point towards the necessity of long-term research on forest regeneration following invasive species removal to understand the feasibility of restoring urban forests to a pre-invaded or desirable condition.