Restoration of sagebrush in crested wheatgrass communities: A longer-term evaluation in the northern Great Basin

Authors: Davies, Kirk; Boyd, Chad; Bates, Jonathan - Jon; Hamerlynck, Erik; Copeland, Stella

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/25/2019
Publication Date: 1/1/2020
Citation: Davies, K.W., Boyd, C.S., Bates, J.D., Hamerlynck, E.P., Copeland, S.M. 2020. Restoration of sagebrush in crested wheatgrass communities: a longer-term evaluation in the northern Great Basin. Rangeland Ecology and Management. 73(1):1-8. https://doi.org/10.1016/j.rama.2019.07.005.
DOI: https://doi.org/10.1016/j.rama.2019.07.005

Interpretive Summary: Crested wheatgrass, an introduced grass, has been seeded on millions of hectares of sagebrush steppe where it establishes near-monoculture communities. Reestablishment of sagebrush in crested wheatgrass stands is needed to increase diversity and improve wildlife habitat. We evaluated broadcast seeding sagebrush and planting sagebrush seedlings across varying levels of crested wheatgrass control for up to nine years post-seeding/planting. Planting sagebrush seedlings in crested wheatgrass stands was vastly more successful at recovering sagebrush cover and density compared to broadcast seeding. Our results suggest that planting sagebrush seedlings can increase diversity in near-monocultures of crested wheatgrass and thereby, improve habitat for sagebrush-associated wildlife. This information is of interest to rangeland and wildlife managers as well as scientists investigating diversifying crested wheatgrass stands.

Technical Abstract: Crested wheatgrass (Agropyron cristatum [L] Gaertm. and Agropyron desertorum [Fisch.] Schult.), an introduced bunchgrass, has been seeded on millions of hectares of sagebrush steppe. It can establish near-monocultures; therefore, reestablishing native vegetation in these communities is often a restoration goal. Efforts to restore native vegetation assemblages by controlling crested wheatgrass and seeding diverse species mixes have largely failed. Restoring sagebrush, largely through planting seedlings, has shown promise in short-term studies but has not been evaluated over longer timeframes. We investigated the reestablishment of Wyoming big sagebrush (Artemisia tridentata spp. wyomingensis [Beetle & A. Young] S.L. Welsh) in crested wheatgrass communities, where it had been broadcast seeded (seeded) or planted as seedlings (planted) across varying levels of crested wheatgrass control with a herbicide (glyphosate) for up to 9 yr post seeding/planting. Planting sagebrush seedlings in crested wheatgrass stands resulted in full recovery of sagebrush density and increasing sagebrush cover over time. Broadcast seeding failed to establish any sagebrush, except at the highest levels of crested wheatgrass control. Reducing crested wheatgrass did not influence density, cover, or size of sagebrush in the planted treatment, and therefore, crested wheatgrass control is probably unnecessary when using sagebrush seedlings. Herbaceous cover and density were generally less in the planted treatment, probably as a result of increased competition from sagebrush. This trade-off between sagebrush and herbaceous vegetation should be considered when developing plans for restoring sagebrush steppe. Our results suggest that planting sagebrush seedlings can increase the compositional and structural diversity in near-monocultures of crested wheatgrass and thereby improve habitat for sagebrush-associated wildlife. Planting native shrub seedlings may be a method to increase diversity in other monotypic stands of introduced grasses.