Short-Term Vegetation Responses to Invasive Shrub Control Techniques for Amur Honeysuckle (Lonicera maackii [Rupr.] Herder)

Abstract

Invasive shrubs in forest understories threaten biodiversity and forest regeneration in the eastern United States. Controlling these extensive monotypic shrub thickets is a protracted process that slows the restoration of degraded forest land. Invasive shrub removal can be accelerated by using forestry mulching heads, but evidence from the western United States indicates that mulching heads can promote exotic species establishment and mulch deposition can reduce native plant species abundance. We compared the effectiveness of the mulching head and the “cut-stump” method for controlling the invasive shrub Amur honeysuckle (Lonicera maackii), as well as their impacts on native plant community recovery, in mixed-hardwood forests of Indiana. After two growing seasons, mulching head treatment resulted in greater L. maackii regrowth and regeneration. The recovery of native plant abundance and diversity following shrub removal did not differ between the two methods. However, mulch deposition was associated with increased abundance of garlic mustard (Alliaria petiolata), an invasive forb. Increasing mulching head treatment depth reduced L. maackii regrowth, but additional study is needed to determine how it affects plant community responses. The mulching head is a promising technique for invasive shrub control and investigating tradeoffs between reducing landscape-scale propagule pressure and increased local establishment will further inform its utility.

Increased light availability due to forestry mowing of invasive European buckthorn promotes its regeneration

“…Some other, less closely related forest invaders have been considered in forestry mower studies, however. For example, Lonicera maackii and Alliaria petiolata have both been shown to be stimulated following shallow forestry mowing with more negative impacts on L. maackii accruing with deeper forestry mowing (Frank et al ), but this is largely a function of disturbance caused by the forestry mower itself—something not included in our experimental design—and not the depth of resulting mulch. We speculate that mechanisms similar to the ones that led to our results would lead to comparable effects in other species, but this remains to be tested.…”

Effects of prescribed grazing by goats on non‐native invasive shrubs and native plant species in a mixed‐hardwood forest

“…However, without follow‐up treatment, the cover of barberry rebounded 40% in 5 years. Frank et al (2018) observed a similar rebound in the cover of L. maackii two‐years following mastication without follow‐up treatments. Maintaining goats on our treatment sites over the 5‐year study prevented a similar recovery of invasive shrubs.…”

“…Reductions in invasive shrubs increase the availability of light in forest understories (Owings et al 2017), which allows the establishment of less shade‐tolerant species. In addition, the herbaceous flora of most forests in the region consists of resilient species that experienced a historic filter of anthropogenic disturbance, including grazing by livestock (Frank et al 2018). Therefore, grazing‐sensitive species may not be present in the seedbanks of many contemporary forests.…”

“…At high densities of invasion, mechanical treatments offer an effective means to control invasive shrubs. While traditional mowing has limited application in a forest setting, mastication with rotary mulching heads attached to more maneuverable motorized equipment has proven effective in controlling invasive shrub species (Ward et al 2013; Frank et al 2018). However, the equipment needed for mastication treatment is expensive and unavailable to many practitioners, resulting in an unfulfilled need for a technique to control extensive and dense invasions of non‐native shrubs in hardwood forests.…”

The effect of a novel herbicide adjuvant in treating Amur honeysuckle (Lonicera maackii)

“…A variety of treatment techniques are used to control invasions of L. maackii (as well as many other woody shrubs); all are included in at least one of the following four categories: physical, biological, cultural, and chemical (Radosevich et al 1997). Physical removal includes manual techniques such as root wrenching, lopping, or root severing (Oneto et al 2010), as well as mechanical removal in the form of brush-cutting and mulching-head treatments (Frank et al 2018). While these methods may disturb the substrate, they are generally considered to be more environmentally safe and can be relatively inexpensive to apply but may require more work hours than other treatments (Bailey et al 2011), and some manual techniques require access to specialized equipment (Frank et al 2018;Oneto et al 2010).…”