Bromus Tectorum L. Also known as cheatgrass is an invasive winter annual grass native to Eurasia. There is an association with cheatgrass and increased bioavailable nitrogen(N) uptake. To explore the effect of competition we have some samples grown with crested wheatgrass (Agropyron cristatum). We are looking at 15N present in above ground shoot tissue as a proxy for microbial N fixation to better understand the genotypic variation in N uptake and life history strategy.