Microstegium vimineum invasion impacts the functioning of archaeal and bacterial nitrification
Invasive species are known to cause shifts in resource availability. Microstegium vimineum--an invasive grass that is disrupting forest ecosystems in the Eastern and Southern U.S.--has been found to increase soil nitrification rates. In this study we investigated how M. vimineum invasion affects the soil microbial communities responsible for nitrification. We used nitrogen potential recovery assays to determine the contribution of different types of nitrifying organisms to the total nitrification rate of invaded and uninvaded forest stands in the Shawnee National Forest. We also used molecular techniques (quantitative PCR and DNA community fingerprinting) to investigate how M. vimineum invasion affects the abundance and community composition of nitrifying microorganisms.
We found that total nitrification potential was higher in invaded plots than in uninvaded plots, and the ammonia-oxidizing archaea showed the greatest invasion-related increase in nitrification rates. We also found that invaded plots contained higher numbers of nitrifying organisms than uninvaded plots, and the community composition of ammonia-oxidizing archaea was significantly altered in invaded plots when compared to uninvaded plots. Our results support previous research that M. vimineum increases nitrification rates. Furthermore, our results link M. vimineum invasion to changes in the activity, abundance, and community composition of the dominant ammonia-oxidizing archaea that contribute the most to the increased nitrification potential of invaded soils. This link between invasive M. vimineum and the soil community can affect availability of nitrogen species in forests soils, which may in turn lead to changes in plant community composition in the wake of this invasion.