In 2002, a 5-acre section of forest at the North Carolina Museum of Art Park underwent an invasive species removal treatment to prevent ecological damage caused by these invasive species and to aesthetically improve the park. Treatment was targeted specifically at non-native woody shrubs, especially Elaeagnus umbellata and Ligustrum sinense. This forested area was used as a case study to examine the effects of invasive species removal on the understory of the forest.
When compared to an adjacent nontreated area of forest, the treatment was effective at decreasing the cover of both Elaeagnus umbellata and Ligustrum sinense. The reduction in invasive shrub cover also increased park sightlines, accomplishing the aesthetic goal. Despite the success of the treatment in removing the target invasive species, eight years later the total cover of invasive species was not different between the two areas. This was largely due to a much higher average cover of Microstegium vimineum in the treated area. Possible explanations for this difference include competitive release and the introduction of disturbance.
There was no observed difference between the understory communities of the nontreated and treated areas. Also, invasive shrub cover was correlated with both canopy cover and proximity to the forest edge. This study shows that successful invasive species removal can lead to further invasion by other species. Furthermore, removal of invasive species may not lead to an increase in native species cover or richness. Finally, this study supports the observation that forest edges and open canopies are often associated with invasion processes.