Management of invasive Pinaceae is imperiled by the lack of invasive ungulate control: successful restoration requires multiple-species management

Abstract

The magnitude and direction of an invasive species’ impact may be determined by its co-existence and interaction with other species. In Argentina, wild boar, red deer, and fallow deer are introduced mammals that have important negative impacts on ecosystems. In Patagonia, nonnative Pinaceae removal programs have been promoted since the 1980s to control exotic conifers and restore native vegetation. The consequences of removing exotic trees without continued management intervention may be unexpected due novel interactions between nonnative species. We evaluate habitat use of introduced ungulates, interactions with native and exotic plants, and their implications for restoration objectives in areas where pines have been removed. Exotic plant species richness and abundance was greater in clear-cuts than native forest or pine plantations. In contrast, richness and abundance of native plants was highest in native forests. Clear-cuts had the highest plant species diversity, primarily driven by high numbers of exotics, relative to native forests. Boar and deer were recorded in clear-cuts, native forests, and pine plantations, but deer were more frequently observed in clear-cuts. Removal of pines created a suitable habitat for deer. The herbivory pressure of deer, coupled with the presence and abundance of invasive plants, can prevent or hinder the establishment and development of native shrubs and trees that are required for the structure and function of the native ecosystem. Although the conditions in clear-cuts present complex challenges for natural regeneration, these sites could be an excellent opportunity for active restoration strategies, by excluding ungulates and controlling exotic plants to promote native species recovery.