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

Graham Frank,Michael Jenkins,Michael Saunders

doi:10.3390/f9100607

Graham Frank, Michael Jenkins + Show 1 more

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https://doi.org/10.3390/f9100607

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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.

Highlights

Throughout the eastern United States, invasive woody shrubs are nearly ubiquitous in hardwood forest understories and pose a serious threat to successful forest management and restoration [1].Examples of these invasive shrubs—mostly introduced in the late 18th to late 19th centuries—include numerous species of bush honeysuckle (Lonicera spp.) as well as Japanese barberry (Berberis thunbergiiDC.), burning bush (Euonymus alatus [Thunb.] Siebold), and others
Sapling-layer honeysuckle were initially reduced from 4005 ± 307 shrubs ha−1 across all pretreatment plots in 2015 to 94 ± 45 shrubs ha−1 in cut-stump removal plots and 110 ± 51 shrubs ha−1 in mulching head treatment plots in 2016
The mulching head treatment was associated with more stems per stump than cut-stump removal (p < 0.01), but mulch itself did not affect stems per stump

Summary

Introduction

Throughout the eastern United States, invasive woody shrubs are nearly ubiquitous in hardwood forest understories and pose a serious threat to successful forest management and restoration [1].Examples of these invasive shrubs—mostly introduced in the late 18th to late 19th centuries—include numerous species of bush honeysuckle (Lonicera spp.) as well as Japanese barberry (Berberis thunbergiiDC.), burning bush (Euonymus alatus [Thunb.] Siebold), and others. Throughout the eastern United States, invasive woody shrubs are nearly ubiquitous in hardwood forest understories and pose a serious threat to successful forest management and restoration [1]. Examples of these invasive shrubs—mostly introduced in the late 18th to late 19th centuries—include numerous species of bush honeysuckle (Lonicera spp.) as well as Japanese barberry DC.), burning bush (Euonymus alatus [Thunb.] Siebold), and others Proliferations of these invasive shrubs can change forest structure by forming dense monotypic thickets in the understory [2]. Between 1994 and 2005, workers in Great Smoky

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