Invasions of Forests in the Eastern United States

Abstract The story of conservation in the eastern United States has historically been one of forest preservation (Whitney 1994; M. Williams 1989). With this story came the dogma that indigenous trees beget a ground layer (plants < 1 m tall) and understory (plants 1–3 m tall) of indigenous herbs and shrubs. In many relatively undisturbed sites this dogma appeared to mesh well with data on the structure and composition of plant communities. To this day, one can find numerous forest preserves in the eastern United States where the ground layer and understory are diverse and composed of indigenous species expressing several functional roles. However, beginning in the early 1970s, ecologists began focusing their attention not just on pristine, remote forested communities but also on forests in populated areas or areas subjected to human disturbance. When asking questions about the effects of fragmentation and historical disturbance, ecologists generated descriptive data; the data revealed forest communities supporting many nonindigenous species.