Herbicide control of the invasive Amur honeysuckle ( Lonicera maackii ) does not alter soil microbial communities or activity

Abstract Invasive plants are a major problem for land managers and have widespread and lasting environmental impacts. The invasive shrub Amur honeysuckle ( Lonicera maackii ) is a pervasive and noxious plant in the Midwest region of the United States. Despite this, many land managers may be uncomfortable with herbicide control of this and other invasive plants due to unknown impacts on ecosystem components including soils. To examine if herbicide control of Amur honeysuckle impacts soil enzyme activity and soil communities, we treated Amur honeysuckle with Garlon ® 4 (triclopyr) suspended in Basal Bark Oil, Basal Bark Oil alone and untreated controls, then assessed soil community, soil enzyme activity and arbuscular mycorrhizal density changes among treatments and across the subsequent growing season. We found that basal bark herbicide treatments of Amur honeysuckle do not negatively impact soil enzyme activity, nor do they impact fungal, prokaryotic or oomycotan diversity or community structure. There was a slight but likely ecologically unimportant effect on community structure associated with basal bark oil applications, but not with herbicide applications. Arbuscular mycorrhizal colonization was negatively affected by herbicide use but this is likely due to reduction in host health and/or mortality. Taken together, this suggests that herbicide control of Amur honeysuckle does not impact soils and land managers can treat these invasive plants without concern for negative soil outcomes.