Technical Abstract: Invasion of the historically perennial-dominated landscapes in the Great Basin by exotic winter annual grasses is one of the most serious plant invasions in North America. Evidence suggests invasive annuals maintain greater growth and competitive ability than native perennials under N-poor and N-rich conditions. The objective of this study was to identify key traits contributing to the success of invasive annual grasses in these environments. Three invasive annual grasses, two native perennial grasses and one introduced perennial grass were exposed to three levels of N supply. Root biomass, root length, root N uptake rate, root and leaf morphology, leaf nitrogen productivity (leaf NP) as well as biomass and N allocation were quantified over four harvests. Path analysis was use to identify major traits influencing variation in N capture among the species. Results indicated that higher leaf NP was the key factor allowing invasive annuals to produce more root biomass and capture more N than native perennial grasses. This suggests variation in leaf NP may be one critical trait determining the ability of the resident plant community to resist establishment of these invaders. Restoration programs may be able to increase weed-resistance by specifically selecting for this trait in revegetation efforts.