Effectiveness of prescribed fire to re-establish sagebrush steppe vegetation and ecohydrologic function on woodland-encroached sagebrush rangelands, Great Basin, USA: Part II: runoff and sediment transport at the patch scale

Authors: Nouwakpo, Sayjro; Williams, Christopher - Jason; Pierson Jr, Frederick; Weltz, Mark; ARSLAN, A. - University Of Nevada; AL-HAMDAN, O.Z. - Texas A&M University

Submitted to: Catena
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/27/2019
Publication Date: 2/1/2020
Citation: Nouwakpo, S.K., Williams, C.J., Pierson Jr, F.B., Weltz, M.A., Arslan, A., Al-Hamdan, O. 2020. Effectiveness of prescribed fire to re-establish sagebrush steppe vegetation and ecohydrologic function on woodland-encroached sagebrush rangelands, Great Basin, USA: Part II: runoff and sediment transport at the patch scale. Catena. 185. https://doi.org/10.1016/j.catena.2019.104301.
DOI: https://doi.org/10.1016/j.catena.2019.104301

Interpretive Summary: Pinyon and juniper woodland encroachment on sagebrush rangelands can negatively alter vegetation structure and ecohydrologic function on these rangelands and thereby limit delivery of ecosystem goods and services. Public and private land managers across the western US are challenged with selecting, applying, and predicting outcomes of various pinyon and juniper removal management practices available for restoring woodland-encroached sagebrush sites. This study employed vegetation measures and rainfall simulation experiments to evaluate ecohydrological impacts of tree removal by prescribed fire at two sites 9 yr after tree removal. Tree removal by prescribed fire was effective at re-establishing perennial grass and forb vegetation in bare areas and the increases in vegetation improved infiltration and reduced high rates of runoff and erosion at both sites over a 9 yr period after treatment. The results demonstrate prescribed fire can be an effective tool for re-establishing an ecological trajectory towards sagebrush steppe vegetation and hydrologic recovery on woodland-encroached sagebrush sites. The study advances our understanding of the benefits of prescribed fire in the restoration of western US sagebrush steppe encroached by pinyon and juniper conifers.

Technical Abstract: Prescribed burning has been proposed and used as a rangeland improvement practice to restore sagebrush steppe encroached by pinyon (Pinus spp.) and juniper (Juniperus spp.) tree species. Short-term effects of burning on the ecohydrologic response of these systems have been well documented and often include a period of increased hydrologic and erosion vulnerability immediately after burning. Long-term ecohydrologic response of sagebrush steppe ecosystems to fire is poorly understood given the preponderance of short-term studies in the literature. This study evaluated vegetation, hydrologic, and erosion responses to tree removal by burning 9 yr after prescribed fire at two sagebrush sites in the Great Basin, USA. Hydrologic and erosion responses on burned plots were evaluated against those of unburned control plots under low (70 mm hr-1) and high (111 mm hr-1) intensity rainfall simulations. Increases in herbaceous vegetation in the shrub-interspace areas (intercanopy area between trees) at both sites 9 years post-fire reduced runoff and erosion during the high intensity rainfall simulations. Herbaceous cover increased by 2- to 4-fold in shrub-interspace areas across the sites due to tree removal by burning and was mostly perennial bunchgrasses 9 yr post-fire. Bare ground (bare soil and rock) in shrub-interspace areas was reduced by tree removal at both sites, but was greater across control and treated conditions 9 yr post-fire at the initially more degraded of the two sites. Reduction of bare ground from 57% to 44% in shrub-interspace areas 9 yr after burning at the less degraded site resulted in nearly 7-fold and 76-fold reductions in runoff and erosion, respectively, during the high intensity rainfall simulations. Reduction of bare ground from 80% to 60% in shrub-interspace areas 9 yr after burning at the more degraded site reduced runoff and erosion from the high intensity rainfall simulations by approximately 3-fold each. Results from both sites indicate tree removal by prescribed fire can increase understory vegetation and thereby improve ecohydrologic function on woodland encroached sagebrush sites over time, but that the magnitude and rate of such improvements are strongly affected by initial vegetation and/or site conditions.