COS 198-6 - Prescribed fire seasonality effects on black greasewood (Sarcobatus vermiculatus) survival and structure in the northern Great Plains

Abstract: Black greasewood (Sarcobatus vermiculatus, Hook., Torr,) is a native halophytic, resprouting shrub common on saline rangelands in the western United States. Due to its aggressive growing nature, greasewood can lead to issues surrounding woody shrub dominance on rangelands where fire has been excluded. In this study, we conducted fall and spring prescribed burns on a degraded rangeland site in Miles City, MT, USA and a healthy rangeland site in Laramie, WY, USA, and recorded greasewood shrub survival, cover and density. We additionally tested whether fuel load impacted shrub response. In MT, we found that shrub canopy cover was reduced in both fall and spring burns (p < 0.001), and shrub canopy cover was projected to recover 4 growing seasons after the prescribed burn. However, shrub density was not impacted by the burn treatments (p = 0.890). In WY, we saw similar results where shrub canopy cover was reduced in both burn treatments (p = 0.007), but shrub density was unaffected (p = 0.749). Shrubs in WY recovered slower than the MT shrubs and were projected to recover 5 growing seasons after the prescribed burn. In MT, there were no differences between seasonality of the prescribed burn for post-fire shrub volume (p = 0.320), as was the case in WY (p = 0.860). We recommend future studies on the impacts frequent-fire-return intervals on greasewood shrubs to potentially combat woody shrub dominance.