Physiochemical drivers of variation in grass invasion impacts on soil carbon cycling
Microstegium Vimineum (Japanese Stiltgrass) is an invasive grass species that is currently dominating susceptible ecosystems across the eastern half of the United States. The presence of Japanese Stiltgrass can result in decomposition of plant available carbon (C) and nitrogen (N), limiting the variety of species that thrive within these habitats. N deposition has the ability to influence the composition of plant communities as it can change the concentration of nitrogen within the atmosphere and rhizosphere. Similarly, leaf litter quality influences microbial communities and therefore available nutrients to understory plants. In this study, we are examining the degree at which these factors influence the impact of Japanese Stiltgrass on soil degradation. The study is taking place in the Shawnee National Forest in southern Illinois. 20 pairs of plots consist of 10 low-quality litter (pine dominated) plots and 10 high-quality litter (6 maple-elm and 4 tulip-poplar dominated) plots. Within each pair, three one-square foot subplots are each receiving one of three nitrogen treatments: 8.65 kg N ha-1 yr-1 or high N, 3.46kg N ha-1 yr-1 or low N, and a control of 0 g N m-2 yr-1. It is anticipated that the highest N treatment levels will yield lesser impacts on the soil in all forest cover types. However, we expect to see the greatest suppression of SOM decomposition under pine-dominated forests, as the microbial communities within these stands are more sensitive to higher levels N additions.