Crested wheatgrass (Agropyron cristatum) seedings in Western Colorado: What can we learn?

Abstract

Non-native species have been widely transported, becoming components of ecosystems worldwide. In some cases this can change thestructure and function of an ecosystem. Crested wheatgrass (Agropyron cristatum, Agropyron spp.) was introduced into the Western U.S. inthe late 18th and early 19th centuries. Since introduction, it has been planted in western rangelands currently occupying millions of acres.Crested wheatgrass causes significant changes in areas where it dominates the vegetation, and restoring rangelands planted with crested wheatgrass to higher plant diversity and ecosystem function has been met with limited success. Here we revisit historical frequency monitoring data collected in western Colorado on public lands that were planted with crested wheatgrass between 1940 and 1980. We also monitored vegetation before and after mechanical treatment (removal of vegetation with the use of a dixie harrow pulled behind a tractor) and re-seeding of desirable species in three areas dominated by crested wheatgrass. We looked for increasing or decreasing trends in plant species, and for plant species that persist with crested wheatgrass. We found that crested wheatgrass increased significantly (p=0.09) over time, we also found five species of grasses, two shrub species, and one forb species that were persistent in areas planted with crested wheatgrass. We found that in mechanically treated areas, the only significant trend was a reduction of native grasses (p<0.05). Our findings suggest that in areas planted with crested wheatgrass, frequency of crested wheatgrass can increase over time. Further, mechanical treatments coupled with seeding were not effective at reducing crested wheatgrass cover, or at increasing native and desirable species. These sites may have experienced a shift to a stable state.

Keywords

• rangeland
• vegetative diversity
• native species
• mechanical treatment
• management