Niche Requirements of an Exotic Invader Across Temperate Forest Gradients

Increasing calls suggest integrating ecological theory into invasive species research, and we use this approach with Microstegium vimineum, an invasive grass in the U.S. that overruns native vegetation in forest understories. Whereas its abundance along roadsides and waterways is taken to indicate that these are dispersal corridors for its propagules, and we confirm the association, we investigate its stage-specific performance as a function of environmental drivers to elucidate a more detailed understanding of its niche requirements. Our study involved a two-tiered, observational approach. We first surveyed M. vimineum across forested and unforested habitats along a 100-km regional gradient from mountains to flatland. This is a common approach for investigating invasive species distributions, but niche differentiation is based on environmental requirements not location. For this reason, we conducted the second tier of our research by measuring stage-specific M. vimineum parameters (cover, biomass and reproduction) as functions of direct rather than proximal environmental drivers (light, litter cover, soil moisture and temperature) in paired invaded and uninvaded plots