Herbicide and Fire Timing Modify Biomass but not Heterogeneity Across Rangelands With Pyric Herbivory

Pyric herbivory is a proven strategy for restoring rangeland heterogeneity, yet how additional management actions—such as altering fire timing or applying herbicide—affect vegetation structure within these systems remains unclear. We manipulated eight large (333–776 ha) landscapes managed with pyric herbivory to evaluate whether fire timing, herbicide application, or their interaction influenced vegetation biomass and structural heterogeneity at two management-relevant scales: the pasture and burn patch. Treatments included dormant- or growing season burn and aerial metsulfuron‑methyl at 33.7 g AI·ha −1 (56 g product·ha −1 ). From 2019 to 2021, we measured biomass and structural heterogeneity, quantified as the standard deviation of biomass within sampling arrays, at the pasture and burn patch scales. Mean biomass ranged from 214.8 g·m −2 to 1 006.2 g·m −2 at the burn patch scale and 325.5 g·m −2 to 855.2 g·m −2 at the pasture scale. Herbicide application reduced biomass by 234.3 g·m −2 2–3 yr after fire; however, neither herbicide, fire timing, nor their interaction affected structural heterogeneity at either scale. Persistent biomass reductions may reduce the availability of high-biomass vegetation structure used by avian species of concern such as Henslow’s Sparrow ( Centronyx henslowii ) and Greater Prairie-Chicken ( Tympanuchus cupido ). Our results highlight ecological trade-offs between broad-scale, command-and-control invasive species management and meeting other objectives in the Great Plains.