Short-Term Response of Native Flora to the Removal of Non-Native Shrubs in Mixed-Hardwood Forests of Indiana, USA

Abstract

While negative impacts of invasive species on native communities are well documented, less is known about how these communities respond to the removal of established populations of invasive species. With regard to invasive shrubs, studies examining native community response to removal at scales greater than experimental plots are lacking. We examined short-term effects of removing Lonicera maackii (Amur honeysuckle) and other non-native shrubs on native plant taxa in six mixed-hardwood forests. Each study site contained two 0.64 ha sample areas-an area where all non-native shrubs were removed and a reference area where no treatment was implemented. We sampled vegetation in the spring and summer before and after non-native shrubs were removed. Cover and diversity of native species, and densities of native woody seedlings, increased after shrub removal. However, we also observed significant increases in L. maackii seedling densities and Alliaria petiolata (garlic mustard) cover in removal areas. Changes in reference areas were less pronounced and mostly non-significant. Our results suggest that removing non-native shrubs allows short-term recovery of native communities across a range of invasion intensities. However, OPEN ACCESSForests 2015, 6 1879 successful restoration will likely depend on renewed competition with invasive species that re-colonize treatment areas, the influence of herbivores, and subsequent control efforts.

Plant community responses to invasive shrub and vine removal in an urban park woodland.

“…Species richness, number of taxa within each growth habit, and total number of families, for native and non-native/invasive species, were calculated and compared with previous studies in the literature. In terms of growth habit, I found that herbs are the most frequent habit by far, which is in agreement with much of the literature (Pyle 1995;Luken et al 1997;Phillips-Mao et al 2014;Shields et al 2015). However, I…”

“…Studies that have examined plant community responses after L. maackii removal found that these sites still contained the exotic shrub as seedlings, but that species richness, abundance, and density of native species all increased significantly in the first few years (Shields et al 2015). This seems to be consistent with what has been observed in Cherokee Park (Carreiro 2014) and is an indication that management and restoration is succeeding in increasing native species richness.…”

“…The removal of densely growing invasive shrubs like L. maackii is often the first step in any restoration plan, since the reduction in canopy cover, and hence the increase in sunlight near the forest floor, is needed to stimulate native herb and tree seed germination and seedling growth (Shields et al 2015). Studies that have examined plant community responses after L. maackii removal found that these sites still contained the exotic shrub as seedlings, but that species richness, abundance, and density of native species all increased significantly in the first few years (Shields et al 2015).…”

“…On the other hand, studies have also found that A. petiolata (Luken et al 1997;Shields et al 2015) abundance tends to increase immediately following removal of L.…”

Removal of invasive shrubs alters light but not leaf litter inputs in a deciduous forest understory

“…Shrub removal experiments of L. maackii have shown positive effects on native annuals and planted native seedlings (Gould & Gorchov ; Hartman & McCarthey ). Observed impacts of invasive species on native are commonly attributed to competition for light (Woods ; Gorchov & Trisel ; Shields et al ).…”