Multi-year drought has persistent forage quality and quantity effects that can be intensified by heavy grazing in semiarid rangelands

Authors: Porensky, Lauren; KOERNER, SALLEY - University Of North Carolina Greensboro; WILLIAMS, AMANDA - Montana State University; VAN EMON, MEGAN - Montana State University; WILCOX, KEVIN - University Of North Carolina Greensboro; KOMATSU, KIMBERLY - University Of North Carolina Greensboro; Dietrich, John; Reinhart, Kurt

Submitted to: Agriculture, Ecosystems & Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/7/2026
Publication Date: 1/23/2026
Citation: Porensky, L.M., Koerner, S.E., Williams, A.R., Van Emon, M.L., Wilcox, K.R., Komatsu, K.J., Dietrich, J.D., Reinhart, K.O. 2026. Multi-year drought has persistent forage quality and quantity effects that can be intensified by heavy grazing in semiarid rangelands. Agriculture, Ecosystems & Environment. 400. Article e110231. https://doi.org/10.1016/j.agee.2026.110231.
DOI: https://doi.org/10.1016/j.agee.2026.110231

Interpretive Summary: Little is known about how multi-year droughts interact with grazing management to affect forage for livestock. In two temperate rangelands, we assessed the separate and combined effects of experimental droughts and grazing management strategies on ruminant forage quality and quantity over five years. During a 2-yr experimental rainfall reduction period, rainfall reductions decreased both forage quality and quantity at one site in Montana. At a second site in Wyoming, reductions were only apparent in heavily grazed plots. In the first year after experimental drought treatments ended, plots that formerly received large rainfall reductions had 26% to 57% less digestible forage biomass but greater forage quality than controls. Increases in forage quality with former drought treatments were strongest in plots that had received heavier grazing. We also observed reductions in forage quality that persisted up to three years after droughts ended. Our results highlight the resilience of forage production in North American Great Plains grasslands to both drought and grazing, but also suggest that these disturbances can have additive and long-term effects on forage nutritive value. Drought effects may impact ungulate nutrition for 1-3 years following a drought, and heavy grazing during drought may strengthen effects of drought on ungulate nutrition.

Technical Abstract: Growing season droughts can have major impacts on grassland vegetation and are predicted to become increasingly frequent in temperate rangelands, but little is known about how droughts and post-drought legacies interact with grazing management to affect forage quality and quantity. In two temperate prairies where grazing by domestic livestock is the primary land-use, we assessed the separate and combined effects of experimental rainfall reductions and grazing management strategies on ruminant forage quality and quantity over five years. To determine forage nutritive value, we measured forage fiber content, organic matter digestibility, relative feed value, forage quantity, and the quantity of digestible forage. During a 2-yr experimental rainfall reduction period, rainfall reductions decreased both forage quality and quantity at one site, while at a second site, reductions were only apparent in heavily grazed plots. In the first year after experimental rainfall reduction treatments ended, plots that formerly received large rainfall reductions displayed strong legacy effects. These plots had 26% to 57% less digestible forage biomass but greater forage quality than controls. Increases in forage quality with former rainfall reduction treatments were strongest in plots that had received heavier grazing during the experimental drought period. Experimental treatments did not induce long-term changes in forage quantity at either site, but we observed reductions in forage quality that persisted up to three years after droughts ended. Our results highlight the resilience of forage production in North American Great Plains grasslands to both drought and grazing, but also suggest that these disturbances can have additive and long-term effects on forage nutritive value. Legacy effects of droughts on forage quality and quantity may impact ungulate nutrition for 1-3 years following a drought, and heavy grazing during drought may strengthen the effects of drought on ungulate nutrition.