Relationship of invasive groundcover plant presence to evidence of disturbance in the forests of the upper midwest of the United States

Nonnative invasive plants (NNIPs) have been introduced to North America by humans since European settlement. Much like other exotic-invasive organisms, NNIPs typically have some advantage over native plants, such as prolific seed production and dispersal. Native forest ecosystems that developed over centuries are limited in their ability to compete against these invaders. Some species, such as kudzu, were deliberately introduced (Mitich 2000), while others were introduced inadvertently, such as in contaminated crop seed. Introduction, however, does not necessarily mean establishment. Although a particular NNIP may have a competitive advantage over native species, timing of emergence and seed dispersal, site quality, and other factors determine whether an NNIP will take hold in an ecosystem. Once established, NNIP threatens the sustainability of native forest composition, structure, function, and resource productivity (Webster et al. 2006).