Removing Chinese privet from riparian forests still benefits pollinators five years later

Abstract

Chinese privet (Ligustrum sinense) is an invasive shrub of the Southeastern U.S. that forms dense stands and limits biodiversity. It was removed from heavily infested riparian forests of the Georgia Piedmont in 2005 by mulching machine or chainsaw felling and subsequent herbicide application. Abundance and species richness of bees and butterflies were sampled using pan traps on removal plots, heavily invaded control plots, and reference plots in 2012, approximately five years after complete removal of privet. Removal plots had nearly three times as many species as control plots and were similar to reference plots in numbers of species. Traps on removal plots captured four times more individuals than those on control plots and similar numbers to reference plots. Bee and butterfly abundance and richness were positively correlated with non-privet plant cover, diversity, and evenness and negatively correlated with privet shrub cover. Removing Chinese privet from riparian forests had a beneficial effect on insect pollinator communities five years after removal and is a relatively simple method of improving pollinator habitat. These findings provide justification for allocating resources for invasive shrub species removal to support long term conservation of these important insect groups and the ecological services they provide.