Coexistence of native and introduced perennial grasses following simultaneous seeding

Revegetation of disturbed semiarid lands requires rapid stabilization of ecological process and soil resources. Introduced species have been widely adopted because the slow establishment of native species frequently results in poor ecosystem recovery and further site degradation. Little research has documented the managerial possibilities and species interactions associated with simultaneously establishing native and introduced grasses on semiarid lands. We conducted a 3-yr experiment at Fort Carson, CO, to evaluate if seven native perennial grasses would coexist with either Russian wildrye [Psathyrostachys juncea (Fisch.) Nevski], crested wheatgrass (Agropyron sp.), or Siberian wheatgrass [A. fragile (Roth) Candargy] after simultaneous seeding. Five grass mixes, each comprised of the seven natives and one introduced grass, and a standard military seed mix (mostly native grasses with a small introduced species component) were evaluated by comparing percentage ground cover of individual species. Predominance of crested and Siberian wheatgrass cover resulted in significantly lower native grass and weed abundance. In contrast, Russian wildrye and military treatments had lower introduced grass cover and high weed abundance, but much higher native grass cover. However, weed cover decreased to < 5% in all treatments during the experiment. Western wheatgrass [Pascopyrum smithii (Rydb.) A. Love] was responsible for > 80% of the native species cover in the military treatment for all 3 yr, whereas the Russian wildrye treatments had a more balanced mix of several native species. These results provide insights into managerial considerations for revegetation and weed control for frequently disturbed rangelands and suggest that some introduced grasses may coexist with native grasses.