Managing invasive Amur honeysuckle ( Lonicera maackii ) in central Kentucky: can native species release and restoration plantings hold their ground?

Abstract Amur honeysuckle [ Lonicera maackii (Rupr.) Herder] is an abundant invasive species throughout Kentucky and the surrounding region. It forms dense stands, outcompeting and displacing native species and adversely impacting the regeneration, succession, and biodiversity of deciduous forest communities. The objective of this study was to compare the efficacy of L. maackii removal alone relative to removal followed by restoration plantings to suppress reinvasion and facilitate forest understory native plant community recovery. In March 2019, a field experiment was conducted with the following treatments: (1) untreated control; (2) L. maackii removal with 0.023 kg ae L −1 glyphosate cut stump application (CH plots); and (3) same treatment as in (2), plus restoration plantings of wildrye grasses ( Elymus spp.) and northern spicebush [ Lindera benzoin (L.) Blume] (CHP plots). Lonicera maackii removal and cut stump glyphosate treatments effectively reduced L. maackii canopy cover, increased herbaceous cover, decreased bare ground, and increased species richness over time compared with untreated plots. However, we did not find any differences (P > 0.05) in L. maackii cover or other plant community variables between CH and CHP treatments over time. Thus, we found insufficient evidence that restoration plantings of Elymus spp. and L. benzoin suppressed L. maackii reinvasion compared with L. maackii removal alone. Spearman rank-correlation tests indicate L. maackii removal correlated with increased herbaceous cover (ρ = −0.75, P < 0.0001), lower bare ground (ρ = 0.714, P < 0.0001), and higher species richness (ρ = −0.693, P < 0.0001). Further studies of L. maackii removal plus restoration plantings are needed that test different species combinations and/or season of planting (i.e., spring vs. autumn) to determine the most effective restoration planting strategy to simultaneously suppress L. maackii reinvasion after removal and facilitate native plant community recovery in forest understories.