Higher Intensities of Mulching-Head Treatments Limit the Response of a Target Invasive Shrub (Lonicera maackii) and Promote Herbaceous-Layer Species Diversity

Abstract Amur honeysuckle ( Lonicera maackii [Rupr.] Herder) and other invasive shrubs represent a serious threat to the biodiversity and ecosystem services of forests in the eastern United States. Treating invasive shrubs can be costly and time consuming, highlighting the need for efficient techniques to control heavy invasions across large areas of forest. Mulching-heads have shown promise for efficiently controlling multiple species of invasive shrubs, including Amur honeysuckle, potentially aiding the restoration of suppressed herbaceous-layer plant communities. In this study, we examined how mulching intensity (i.e., treatment depth below the soil surface) affects Amur honeysuckle sprouting response, as well as the post-treatment response of the plant community. We found that deeper applications of a mulching-head inhibited the post-treatment regrowth of Amur honeysuckle sprouts. According to NMDS analysis, post-treatment species composition became more similar across plots and shifts in post-treatment axis values were associated with increased species diversity and floristic quality, a measure of species conservation value. Additionally, a canonical correspondence analysis revealed that deeper mulching-head intensities were correlated with increased herbaceous-layer plant species diversity and floristic quality. We conclude that mulching-head treatments are an effective technique for controlling invasive shrubs without degrading native plant communities, and deeper treatments reduce the rate of post-treatment sprouting.