Prescribed summer fire and seeding applied to restore juniper-encroached and exotic annual grass-invaded sagebrush steppe

Authors: Davies, Kirk; DEAN, ALISON - Bureau Of Land Management

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/22/2019
Publication Date: 7/1/2019
Citation: Davies, K.W., Dean, A.E. 2019. Prescribed summer fire and seeding applied to restore juniper-encroached and exotic annual grass-invaded sagebrush steppe. Rangeland Ecology and Management. 72(4):635-639. https://doi.org/10.1016/j.rama.2019.03.006.
DOI: https://doi.org/10.1016/j.rama.2019.03.006

Interpretive Summary: Western juniper encroachment and exotic annual grasses (medusahead and cheatgrass) invasion of sagebrush communities decrease ecosystem services and degrade ecosystem function. We evaluated summer applied prescribed fire and seeding to restore these communities. Prescribed burning removed all juniper and initially reduced medusahead cover, but did not influence cheatgrass cover. Neither the native nor introduced seed mix were successful at increasing large bunchgrass cover, and six years post-fire, medusahead cover was greater in burned treatments compared to the unburned treatment. We suggest that additional treatments, such as pre-emergent herbicide control of annuals and possibly multiple seeding events, would be needed to restore sagebrush communities that are juniper-encroached and annual grass-invaded.

Technical Abstract: Western juniper (Juniperus occidentalis Hook.) encroachment and exotic annual grass (medusahead [Taeniatherum caput-medusae L. Nevski] and cheatgrass [Bromus tectorum L.]) invasion of sagebrush (Artemisia L.) communities decrease ecosystem services and degrade ecosystem function. Traditionally, these compositional changes were largely confined to separate areas, but more sagebrush communities are now being altered by both juniper and exotic annual grasses. Few efforts have evaluated attempting to restore these sagebrush communities. The Crooked River National Grassland initiated a management project to restore juniper-encroached and annual grass-invaded sagebrush steppe using summer (mid-July) applied prescribed fires and post-fire seeding. Treatments were unburned, burned, burned and seeded with a native seed mix, and burned and seeded with an introduced seed mix. Prescribed burning removed all juniper and initially reduced medusahead cover, but did not influence cheatgrass cover. Neither the native nor introduced seed mix were successful at increasing large bunchgrass cover, and six years post-fire, medusahead cover was greater in burned treatments compared to the unburned treatment. Large bunchgrass cover and biological soil crusts were less in treatments that included burning. Exotic forbs and bulbous bluegrass (Poa bulbosa L.), an exotic grass, were greater in burned treatments compared to the unburned treatment. Sagebrush communities that are both juniper-encroached and exotic annual grass-invaded will need specific management of both juniper and annual grasses. We suggest that additional treatments, such as pre-emergent herbicide control of annuals and possibly multiple seeding events, would be needed to restore these communities. We recommend an adaptive management approach where additional treatments will be applied based on monitoring data. Restoration of these communities will likely require multiple treatments.