Importance of phytobiomass and ungulates to hydrologic function in a temperate grassland

Authors: Reinhart, Kurt; Vermeire, Lance

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/26/2021
Publication Date: 6/4/2021
Citation: Reinhart, K.O., Vermeire, L.T. 2021. Importance of phytobiomass and ungulates to hydrologic function in a temperate grassland. Rangeland Ecology and Management. 78:1-4. https://doi.org/10.1016/j.rama.2021.04.009.
DOI: https://doi.org/10.1016/j.rama.2021.04.009

Interpretive Summary: Problem- Mismanagement of livestock grazing may contribute to hydrologic dysfunction of rangelands. Hydrologic dysfunction likely depends on two opposing biophysical drivers, compaction by livestock and bioturbation by plant roots and soil biota. These two biophysical drivers are often inseperable in field. To help improve management of grasslands and to avoid desertification, we conducted a field experiment to determine which is the main driver of hydrologic dysfunction. Accomplishment- Compaction by ungulates is a main driver of hydrologic dysfunction of grazinglands, especially when compaction forces are applied to fine textured soils and/or when soils are vulnerable to compaction (e.g. wet, not well vegetated).

Technical Abstract: In grazinglands, hydrologic dysfunction likely depends on two opposing biophysical drivers, compaction by livestock and bioturbation by plant roots and soil biota. To understand which is most important, we conducted a long-term field experiment. We tested the effects of phytobiomass (control versus herbicide treated) and three ungulate disturbance treatments (none, once, and twice disturbed) on soil water transport in northern mixed-grass prairie. Field-saturated hydraulic conductivity (i.e. infiltration) was primarily reduced by the most severe (twice disturbed) ungulate disturbance treatment. To a lesser degree, ungulate disturbance and phytobiomass interacted, and similar levels of hydrologic dysfunction were detected for plots annually treated with herbicide and disturbed by a single livestock disturbance event (and while soils were dry and resistant to compaction) and naturally vegetated plots that had been twice disturbed (including while soils were wet and susceptible to compaction). Our findings suggest compaction by ungulates is a main driver of hydrologic dysfunction of grazinglands, especially when biocompaction forces are applied to fine textured soils and/or when soils are vulnerable to compaction (e.g. wet, not well vegetated).