The dual invasion of Amur honeysuckle and Emerald Ash Borer alters fungal driven decomposition in Midwestern forests

Abstract

Abstract Midwestern forests are currently impacted by two prominent invaders, the Emerald Ash Borer (EAB), Agrilus planipennis and Amur honeysuckle, Lonicera maackii. The loss of ash (Fraxinus spp.) trees due to EAB invasion can further facilitate honeysuckle invasion, driving changes in the composition of forest leaf litter. To evaluate the extent to which these changes alter ecosystem function, we conducted litter bag and culture-based decomposition experiments using leaf litter from sugar maple (Acer saccharum), oak (Quercus spp.), black ash (Fraxinus nigra), green ash (Fraxinus pennsylvanica), spicebush (Lindera benzoin), and Amur honeysuckle (Lonicera maackii). To further understand the mechanism driving differences in decay rates, we inoculated six species of decomposing fungi separately onto both single species and multispecies (half honeysuckle and half native species) leaf litter and measured decomposition rate, fungal growth and enzymatic activity in laboratory-based cultures. Honeysuckle leaf litter decomposed faster, had increased fungal growth, and had higher activity for carbon degrading enzymes compared to native species leaf litter. Furthermore, multispecies mixtures followed the same patterns as honeysuckle, suggesting that the addition of honeysuckle to leaf litter will accelerate ecosystem functions related to carbon breakdown. Consequently, forests that experience the invasion of honeysuckle and EAB induced loss of ash are likely to have faster rates of decomposition, potentially resulting in an influx of available nutrients.