Prescribed fire and exotic plant responses in phreatophytic Sarcobatus vermiculatus rangelands with contrasting degradation

Authors: WADE, NATHAN - Forest Service (FS); Vermeire, Lance; SCASTA, J. DEREK - University Of Wyoming

Submitted to: Global Ecology and Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/15/2024
Publication Date: 4/16/2024
Citation: Wade, N.M., Vermeire, L.T., Scasta, J. 2024. Prescribed fire and exotic plant responses in phreatophytic Sarcobatus vermiculatus rangelands with contrasting degradation. Global Ecology and Conservation. 52. Article e02955. https://doi.org/10.1016/j.gecco.2024.e02955.
DOI: https://doi.org/10.1016/j.gecco.2024.e02955

Interpretive Summary: Fire is a major ecological process in arid rangelands in the western United States. Yet, interactions between fire, grazing, and exotic species invasion persist for many rangelands with a lack of knowledge for wide-spread but undervalued ecosystems such as black greasewood (Sarcobatus vermiculatus) plant communities. The impacts of reintroducing fire in the fall and spring on community composition and current-year biomass were evaluated at two such sites, one dominated by exotic annual cool-season grasses in Miles City, MT, USA, and one dominated by native perennial warm-season grasses in Laramie, WY, USA. Study sites were assessed based on Ecological Site Description (ESD) and State-and-Transition Models (STMs). Experimental designs at both sites included spring and fall burns applied to 400 m2 plots. No fire was applied before the baseline sampling in the summer of 2020, fall fires were applied in the fall of 2020, and spring fires were applied in the spring of 2021. Vegetation responses to treatments were assessed in the summer of 2021 and 2022 and compared to unburned control plots. Exotic species such as Japanese brome were reduced in fall burned plots over the course of the study in MT and cheatgrass did not increase in spring or fall burned plots in WY. The proportion of native species in both plant communities remained constant and native perennial warm-season grasses such as alkali sacaton were resilient to fire. Moreover, burn treatment had no negative effects on plant diversity in either location. Fire treatments had variable effects on current-year biomass with influences of drought and season of burn. Analyses suggest plant communities differed between locations with no fire treatment effect. Prescribed fire, regardless of season, did not exacerbate exotic plant species spread or reduce native species dominance in either location – suggesting that greasewood rangelands are resilient to fire. Future research can investigate the use of prescribed fire with other methods such as revegetation and herbicide application in reducing exotic dominance and increasing native dominance.

Technical Abstract: Fire is a major ecological process in arid rangelands in the western United States. Yet, interactions between fire, grazing, and exotic species invasion persist for many rangelands with a lack of knowledge for wide-spread but undervalued ecosystems such as black greasewood (Sarcobatus vermiculatus) plant communities. The impacts of reintroducing fire in the fall and spring on community composition and current-year biomass were evaluated at two such sites, one dominated by exotic annual C3 grasses in Miles City, MT, USA, and one dominated by native perennial C4 grasses in Laramie, WY, USA. Study sites were assessed based on existing Ecological Site Description (ESD) and State-and-Transition Models (STMs) and were found to be contrasting in terms of degradation. Experimental designs at both sites included randomized complete block designs with spring and fall burns applied to 400 m2 plots. No fire was applied before the baseline sampling in the summer of 2020, fall fires were applied in the fall of 2020, and spring fires were applied in the spring of 2021. Vegetation responses to treatments were assessed in the summer of 2021 and 2022 and compared to unburned control plots. Exotic species such as Bromus arvensis were reduced in fall burned plots over the course of the study in MT and Bromus tectorum did not increase in spring or fall burned plots in WY. Accordingly, the proportion of native species in both plant communities remained constant and native perennial C4 grasses such as Sporobolus airoides were resilient to fire. Moreover, burn treatment had no negative effects on plant species richness, evenness, or diversity in either location. Fire treatments had variable effects on current-year biomass with variable influences of drought and season of burn. A Nonmetric Multi-Dimensional Scaling (NMDS) analysis using Bray-Curtis distances as an indicator of dissimilarity suggests locations were botanically dissimilar with no discernible fire treatment effect. Prescribed fire, regardless of season, did not exacerbate exotic plant species spread or reduce native species dominance in either location – suggesting that phreatophytic S. vermiculatus rangelands are resilient to anthropogenic burning. Future research can investigate the use of prescribed fire with other methods such as revegetation and herbicide application in reducing exotic dominance and increasing native dominance.