Native Plant Functional Traits Influencing the Early Growth of Japanese Barberry in Eastern Deciduous Forests of the United States

<jats:p> Greenhouse experiments in invasion ecology have proven valuable for uncovering the mechanisms behind plant invasions (Ehrenfeld 2003). Their controlled environmental conditions allow researchers to isolate and examine specific ecological processes (Zanetti et al. 2020). A widely distributed invasive species in the Eastern Deciduous Forests of North America is Japanese Barberry ( <jats:italic>Berberis thunbergii</jats:italic> ), an introduced shrub known to colonize both highly disturbed and relatively undisturbed forests (Harrington et al. 2004). Feral populations of this species are commonly found in forest understories, where dense infestations hinder native plant regeneration. One of the major concerns after the removal of invasive shrubs is their potential regrowth and the difficulty of reestablishing native plant species that can successfully outcompete and control the infestation (Weidlich et al. 2020; D'Antonio and Meyerson 2002). To gain a deeper understanding into the role of native species in suppressing reinvasion, we grew the native forb Heath Aster ( <jats:italic>Symphyotrichum ericoides</jats:italic> ) together with the invasive shrub in soil collected from a forest heavily infested by Japanese Barberry, where the species relative aboundance is approximately 60% within the shrub community (Fig. 1). Our experiment is the first to examine seed germination and early growth of both species simultaneously. Additionally, the presence of other native species emerging from the soil seed bank provided key insights into the functional traits required for native competitors to more effectively outperform Japanese Barberry propagules under current and projected climate scenarios in central Pennsylvania. </jats:p>