Fire seasonality and herbicide effects on Sarcobatus vermiculatus survival and structure in western Great Plains

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

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/5/2024
Publication Date: 3/7/2024
Citation: Wade, N.M., Vermeire, L.T., Scasta, J. 2024. Fire seasonality and herbicide effects on Sarcobatus vermiculatus survival and structure in western Great Plains. Rangeland Ecology and Management. 94:64-73. https://doi.org/10.1016/j.rama.2024.02.001.
DOI: https://doi.org/10.1016/j.rama.2024.02.001

Interpretive Summary: Black greasewood (Sarcobatus vermiculatus) is a native salt-tolerant, resprouting shrub common on rangelands in the western United States. Stands can become dense, with limited native herbaceous biomass, and are prone to invasion by exotic species. We tested fall and spring prescribed fire compared to nonburned controls in a degraded rangeland site in Miles City, MT, USA and a healthy rangeland site in Laramie, WY, USA to determine effects on greasewood shrub survival, density and canopy structure. We additionally tested fuel load, time since fire, fire seasonality and pre-fire measurement effects on post-fire greasewood canopy structure. In a second experiment at the Montana site only, nontreated controls, fall fire, 2,4-D and 2,4-D preceded by fire were tested for effects on herbaceous biomass and greasewood survival, density and canopy structure. Fire did not affect greasewood survival, but fire in either season reduced canopy volume 52% across two growing seasons and models projected 4 or 5 growing seasons for structural recovery. Fine fuel load was negatively related to greasewood density and canopy structure. Herbicide reduced greasewood survival 55% and fire plus herbicide reduced survival 30%. No treatment effects were detected for herbaceous biomass at the degraded site. Prescribed fire can reduce greasewood canopy structure for multiple years without killing the shrubs. Herbicide is more effective than fire if the objective is to reduce greasewood density, but multiple applications may be required.

Technical Abstract: Black greasewood (Sarcobatus vermiculatus) is a native salt-tolerant, resprouting shrub common on rangelands in the western United States. Stands can become dense, with limited native herbaceous biomass, and are prone to invasion by exotic species. We tested fall and spring prescribed fire compared to nonburned controls in a degraded rangeland site in Miles City, MT, USA and a healthy rangeland site in Laramie, WY, USA to determine effects on greasewood shrub survival, density and canopy structure. We additionally tested fuel load, time since fire, fire seasonality and pre-fire measurement effects on post-fire greasewood canopy structure. In a second experiment at the Montana site only, nontreated controls, fall fire, 2,4-D and 2,4-D preceded by fire were tested for effects on herbaceous biomass and greasewood survival, density and canopy structure. Fire did not affect greasewood survival, but fire in either season reduced canopy volume 52% across two growing seasons and models projected 4 or 5 growing seasons for structural recovery. Fine fuel load was negatively related to greasewood density and canopy structure. Herbicide reduced greasewood survival 55% and fire plus herbicide reduced survival 30%. No treatment effects were detected for herbaceous biomass at the degraded site. Prescribed fire can reduce greasewood canopy structure for multiple years without killing the shrubs. Herbicide is more effective than fire if the objective is to reduce greasewood density, but multiple applications may be required.