The Effects of NH4NO3 Treatments on Melilotus Officinalis and Native Diversity in a Montane Grassland

Wolf, Joy

In this study, NH4NO3 was added to plots placed inside, along the edge, and outside patches of invasion in an attempt to augment nitrogen and promote native establishment. Fertilizing increased total species richness, grass richness, and native percent cover, while Melilotus cover decreased. In Rocky Mountain National Park (RMNP), Melilotus officinalis and M. alba can establish as patches in disturbed areas in the montane grasslands. In a previous study Melilotus-invaded patches in RMNP had higher exotic, forb and annual species richness, lower native, grass and perennial species richness, and lower nitrogen levels than non-invaded grasslands. In this study, NH4NO3 was added to plots placed inside, along the edge, and outside patches of invasion in an attempt to augment nitrogen and promote native establishment. Fertilizing increased total species richness, grass richness, and native percent cover, while Melilotus cover decreased. New species established in fertilized plots. Although nitrogen can facilitate exotic invasion, this study showed that in certain situations nitrogen fertilization can suppress Melilotus and facilitate native species. This study brings to light the complexity of biological invasion and eradication of nitrogen fixing species and presents encouraging data to land managers who work in unique plant communities. [Key Words: Biological invasion, montane grassland, nitrogen, Melilotus]