Too much of a good thing: Models of a potential bioenergy crop (Miscanthus x giganteus) indicate a high risk of biological invasion but show that certain communities may be resilient
In light of global climate change there is mounting interest in identifying alternative, carbon-neutral energy sources that can be used broadly. Large-scale production of biofuels offers one strategy to address this problem and there is significant interest in using perennial crops such as Miscanthus x giganteus for this purpose as they are prolific growers, have low nutrient requirements, and are drought and cold tolerant. However, the same properties that make such species excellent biofuel candidates also give them a high potential of becoming invasive species that can strongly alter natural communities. We use an empirically parameterized and spatially-explicit simulation modeling approach to explore the potential invasion dynamics of Miscanthus into complex landscapes with different habitat characteristics and community compositions. We analyzed a range of models that incorporated different ecological processes (rhizomal or seed dispersal, incorporation of intra- and interspecific competition, habitat modification), landscape characteristics (habitat quality, spatial arrangement, dispersal pathways), and management tactics to evaluate their relative influences on community dynamics. Using these models we were able to explore characteristics of invasion dynamics in complex landscapes while also making predictions about how different management strategies could affect the spatial and temporal characteristics of Miscanthusinvasions.
Demographic traits of Miscanthus such as high fecundity, survival, and growth allowed it to readily dominate many landscapes indicating a high risk of invasiveness. Comparisons among simulations showed that the potential for long-distance dispersal through viable seeds drastically increased invasiveness and limited the effect of most management practices. However, over shorter time scales certain management practices such as the inclusion of buffer zones or earlier harvests could reduce the rate and/or extent of spread. The inclusion of intraspecific competition in models limited population sizes and the rate of spread but had less of an effect on the qualitative dynamics (i.e. invasions still readily occurred). Habitats with interspecific competitors (such as natural grassland communities) were able to resist invasion under certain conditions suggesting some ecosystems may be naturally resilient. This approach also offered a method to evaluate community characteristics for their effect on resilience to invasion and to predict areas that may be more or less susceptible to invasion. While these models are designed around invasion of Miscanthus x giganteus, we believe this approach is flexible enough to be applied to a wide variety of systems and can be used to understand the spatial dynamics of competition and invasion more generally.