How did Joan Ehrenfeld change our perspective on plant invasions by incorporating an ecosystem perspective? Ehrenfeld’s early contributions in ecology were centered on the New Jersey pine barrens, and addressed fundamental questions, largely in plant community ecology. Even in her earlier work, however, she was interested in the interaction between above- and belowground interactions, in questions such as how roots interacted with the organisms and physical characteristics of the rhizosphere, and how plants affected and were affected by soil chemistry. When she published her first paper on biological invasions in 1997, she was at the leading edge of the avalanche of literature on biological invasions. Even at this early point, she was interested in incorporating an ecosystem perspective and in considering the conservation and restoration implications of plant invasions.
Results/Conclusions
While most of the work on plant invasions has focused on individual species, Ehrenfeld stressed a more holistic and integrative perspective. Her influence changed the study of the impact of plant invasions on ecosystem processes from an area that few were aware of, to a major focus of ecological research. Due in part to her influence, we now have a far better understanding of how feedbacks between invasive plants and the soil environment can alter ecosystem properties. Her interests in how ecosystem dynamics are altered by invasive plants and animals addressed a multitude of interacting causal pathways. Much remains to be learned, including the frequency and magnitude of such effects, and how these interactions scale up to landscape, regional and global effects. Ehrenfeld’s work on the effects of exotic plant invasions on the soil microbial community and on soil nutrient cycling fundamentally changed the way ecologists conceptualize the impacts of plant invasions; the work she carried out at the end of her life greatly expanded this perspective to the complex interactions by which both exotic plants and animals result in ecosystem alterations.