Variation in carbon cycling impacts of an invasive grass (Microstegium vimineum) across an urban-rural gradient in Southern Appalachian forests

Although there is broad recognition that invasive species can alter ecosystem processes, little is known about how other factors influence such impacts. Recent work demonstrates that factors such as initial site conditions and native plant community composition are important for understanding the impacts of invasive plants. Land use may be an important determinant of invader impacts because human activities modify environmental conditions in ways that can enhance invader fitness. In this study, we examine how the ecosystem-level impacts of an aggressive understory invader, Microstegium vimineum, vary in forests spanning an urban-rural gradient near Asheville, NC. Previous work shows that M. vimineum presence is associated with diminished soil carbon (C) pools. Thus, we focus on soil C pools and litter decomposition, a major C flux. In October 2011, we established paired invaded-uninvaded plots in forests within an urban, rural, or forested matrix. Within each plot, we are conducting a litterbag experiment and collecting soil to resolve C pools into microbial biomass, mineralizable, root biomass particulate organic, and total organic C. Preliminary results indicate additive effects of land use and M. vimineum invasion on litter decomposition, such that litter decomposition is progressing most rapidly in rural, invaded forests. Future work will include assessing the functional response of the microbial community to M. vimineum invasion at these sites. The results of this work will provide new insights about how invasive species’ impacts vary across space. Understanding this variation is crucial for prioritizing management targets and predicting the ecosystem-level consequences of invasion across heterogeneous landscapes.