Patch-burn grazing increased structural heterogeneity in southwestern North Dakota rangelands

Authors: Spiess, Jonathan; McGranahan, Devan; HOVICK, TORRE - North Dakota State University; BERTI, MARISOL - North Dakota State University; GASCH, CALEY - University Of Alaska; GEAUMONT, BENJAMIN - North Dakota State University

Submitted to: Applied Vegetation Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/20/2025
Publication Date: 2/28/2025
Citation: Spiess, J.W., McGranahan, D.A., Hovick, T.J., Berti, M., Gasch, C.K., Geaumont, B.A. 2025. Patch-burn grazing increased structural heterogeneity in southwestern North Dakota rangelands. Applied Vegetation Science. 28(1). Article e70016. https://doi.org/10.1111/avsc.70016.
DOI: https://doi.org/10.1111/avsc.70016

Interpretive Summary: Vegetation structure is an ecosystem property commonly used to evaluate rangeland suitability for wildlife that is affected by community composition and management. We investigated using patch-burn grazing with either sheep or cow-calf pairs to increase the variability of vegetation structure on lower diversity grassland pastures in southwestern North Dakota over four grazing seasons. We measured structural characteristics and plant community composition each year on the patch-burn grazing cattle and sheep pastures. We found that structural characteristics were significantly influenced by the fire and grazing disturbances with recently burned patches being different from other patches for most structural characteristics and that the variability of vegetation structure increased over time. This study supports the expectation that patch-burn grazing will increase the variability of vegetation structures present on rangelands that wildlife can use.

Technical Abstract: Persistent land use change throughout the North American Great Plains increases the need to maintain and improve ecosystem service delivery from remaining rangelands to meet production and conservation goals. In this study, we investigated the efficacy of patch-burn grazing to increase structural heterogeneity on semi-arid post-Conservation Reserve Program grasslands in southwestern North Dakota. We surveyed plant community composition and structural characteristics in patch-burn grazing pastures during the 2017 – 2020 summer grazing seasons. Three pastures were stocked with cow-calf pairs and three stocked with sheep. We also surveyed structural characteristics on units with conventional management (hay or idle) for active and post-CRP enrolled grasslands during summers 2018 – 2020. We tested for vegetative and structural differences between patches with varying time since fire and between grazer type on patch-burn pastures using mixed-effect models and ordination. We used variance partitioning to determine if structural contrast on patch-burn pastures increased over the study period and if structural contrast was higher on patch-burn grazing pastures relative to conventional management. Time since fire was significant for all structural characteristics with recently burned patches being different from other patches. There were no structural differences between cattle and sheep pastures, but forb and legume cover were lower in sheep pastures. Structural contrast on patch-burn pastures increased over the study and was greater than conventional management. Increased structural heterogeneity is important for supporting a broad suite of rangeland wildlife and can stabilize forage production. This study supports the expectation that patch-burn grazing with moderate stocking rates will increase structural contrast regardless of grazer type, but practitioners should consider which suites of species that management may benefit.