ABSTRACT

Persistent colonies composed of invasive woody perennials alter the structure and function of forest ecosystems by inhibiting the growth and development of native species (Webster et al. 2006). The ability of these species to inhibit the recruitment of native species raises the possibility that large-scale invasionsmay fundamentally change the successional trajectory of forest ecosystems. Such a change would have far-reaching implications for numerous plant and animal species that rely on native plant communities and their successional pathways. For example, research byBrown et al. (2006) in the LuquilloMountains of Puerto Rico suggests that invasion by the invasive tree Syzygium

jambos has produced a new vegetation assemblage, which is likely to foster long-term changes in community structure, composition, and successional trajectory. Similarly, in the eastern United States, the small shade-tolerant, invasive tree Rhamnus frangula aggressively invades forest understories, forming dense thickets that inhibit tree regeneration and reduce herbaceous layer cover and species diversity (Frappier et al. 2003a; Fagan and Peart 2004). Invasions by woody perennials into nonforested habitats have also had significant consequences for local plant and animal communities (Braithwaite et al. 1989; Knopf 1994; Bruce et al. 1995). More cryptic, but equally weighty, changes may arise from an invader’s influence on nutrient cycling (Rice et al. 2004) even if it does not completely replace the native overstory.