Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Roughing up smooth brome and dethroning crested wheatgrass with native plants: dominant to subordinate on Utah rangeland.

Abstract

The vast plantings of smooth brome (Bromus inermis Leyss. [Poaceae]) and crested wheatgrass (Agropyron cristatum (L.) Gaertn. [Poaceae]) throughout the Intermountain West have come under scrutiny for their lack of native plant diversity. We looked at the results of 2 projects that were intended to introduce native plant diversity into monocultures of smooth brome and crested wheatgrass in central and western Utah 20 y ago. Results immediately following the crested wheatgrass planting were impressive, though subsequently the native plants became largely extirpated. The initial results following the smooth brome planting were dismal, but decades later a diverse native plant community had developed. Under the pressures of historic overgrazing, soil erosion, climate change, weed invasion, and frequent fire, a reasonable question is whether restoration of disturbed sites can approximate pre-European settlement plant communities. Significant work on native species plant material development and seed transfer zones have at their core sentiment the return to native communities. The case studies in this article, while limited in scope, indicate that early plantings of well-adapted introduced grasses have become naturalized to these systems and can be temporarily displaced but not removed. They provide important elements of functional stability but are limited in the attributes associated with more diverse native plant communities. A model of augmentation that inserts competitive native plants into established introduced grass stands has the best chance of achieving the combination of site stability with other ecosystem services. The longevity and resilience of the native plant augmentations, however, remain uncertain under continuing and developing perturbations.