Sensitivity of soil nutrient pools, but stability of microbial processes, under reduced rainfall and altered grazing management in northern mixed-grass prairie

Authors: KOMATSU, KIM - University Of North Carolina Greensboro; Reinhart, Kurt; ALLEY, SARAH - Smithsonian Environmental Research Center; Porensky, Lauren; WILCOX, KEVIN - University Of North Carolina Greensboro; KOERNER, SALLY - University Of North Carolina Greensboro

Submitted to: Soil Biology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/13/2025
Publication Date: 12/14/2025
Citation: Komatsu, K.J., Reinhart, K.O., Alley, S., Porensky, L.M., Wilcox, K.R., Koerner, S.E. 2025. Sensitivity of soil nutrient pools, but stability of microbial processes, under reduced rainfall and altered grazing management in northern mixed-grass prairie. Soil Biology and Biochemistry. 214. Article 110071. https://doi.org/10.1016/j.soilbio.2025.110071.
DOI: https://doi.org/10.1016/j.soilbio.2025.110071

Interpretive Summary: Problem: Little is known about the interplay between grazing and drought on soil health indicators of natural rangelands (i.e. prairies). Approach: We used an innovative field experiment to enable understanding the relative importance of rainfall reduction, bovine grazing, and their interplay on soil nutrient pools and processes during and after treatments. Findings: Rainfall reductions decreased soil phosphorus and soil micronutrients. Conversely, rainfall reductions increased soil nitrate. Nutrients were unaffected by grazing treatments. Furthermore, soil biotic properties (e.g. extracellular enzyme activities, soil bacteria, and soil fungi) were relatively resistant to rainfall reduction treatments. Conclusions: Our results highlight the relative stability of belowground processes in semi-arid rangelands in the face of drought and land management strategies.

Technical Abstract: Nutrient cycling is a key ecosystem service provided by soils, which may be impacted by global change-induced droughts and alterations to grazing pressure. While the belowground abiotic and biotic responses to drought are increasingly studied, linkages among plant, animal, and microbial responses to drought remain poorly understood. Here we used an innovative experimental approach to enable understanding the relative importance of rainfall reduction, bovine grazing, and their interplay on soil nutrient pools and processes during and after treatments. Specifically, we experimentally imposed a two-year drought of varying intensity (five levels) at two northern mixed-grass prairie sites in Montana and Wyoming. Crossed with this drought treatment, we also imposed a gradient of bovine grazing pressure during the two drought years and three years of recovery following the drought. We found that rainfall reductions at both sites resulted in reductions in soil available P and micronutrients during treatment application. Conversely, rainfall reductions caused both immediate and persistent increases in soil NO3. Soil nutrients were generally unaffected by grazing treatments. In contrast, biotic soil properties including the activities of six extracellular enzymes and bacterial and fungal community compositions were relatively resistant to rainfall reduction treatments. However, grazing treatments appeared to have a greater effect on extracellular enzyme activity potentials and soil microbial community composition. Overall, our results highlight the relative stability of belowground processes in semi-arid rangelands in the face of drought and land management strategies.