Moderate grazer density stabilizes forage availability more than patch burning in low-stature grassland

Authors: Raynor, Edward; McGranahan, Devan; MILLER, JAMES - University Of Illinois; SCHACHT, WALTER - University Of Nebraska; DEBINSKI, DIANE - Montana State University; ENGLE, DAVID - Oklahoma State University

Submitted to: Land
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/7/2021
Publication Date: 6/9/2021
Citation: Raynor, E.J., McGranahan, D.A., Miller, J.R., Schacht, W.H., Debinski, D.M., Engle, D.M. 2021. Moderate grazer density stabilizes forage availability more than patch burning in low-stature grassland. Land. 10:395. https://doi.org/10.3390/ijms22083894.
DOI: https://doi.org/10.3390/ijms22083894

Interpretive Summary: This article evaluates the role of stocking rate and pasture management with fire on temporal stability of forage availability in tall fescue-dominated pastures in Iowa. Tall fescue is a popular non-native forage species used throughout the southeastern United States as well as other regions, where a reliable forage is desired. An examination of patch burn-grazed pastures and uniformly burned-grazed pastures under heavy, low, and moderate stocking rates revealed neither fire regime predicted stability of forage availability, whereas high stability of forage availability was driven by moderate stocking. These findings add to the growing literature that conservative stocking can help managers in mesic, non-native pasture-lands reduce risk in grazing operations regardless of fire management practice.

Technical Abstract: Livestock production is an important industry in the tallgrass prairie ecoregion of the eastern US Great Plains but invasion by non-native C3 grasses (e.g., tall fescue Schedonorus arundinaceus) and overgrazing have caused substantial degradation. Lower plant diversity and overgrazing might increase temporal variability in forage availability thereby reducing the capacity of grassland to produce temporally stable ecosystem services such as forage provisioning. Because prescribed fire is becoming more common in the region, managers should understand the effects of fire regime and the role of varying levels of grazing intensity on stability of forage availability in invaded grasslands. This study examined the stability of forage availability and test for diversity-stability mechanisms in southern Iowa, USA, through three periods of grazing intensity: heavy stocking rate, light stocking rate, and moderate stocking rate. All pastures were treated with one of two different fire regimes: patch-burning, with one-third of the pasture burned each year, or complete burns every third year. Moderate stocking rates had the least temporal variability of forage availability, regardless of fire regime. Likewise, statistical evidence for a portfolio effect was found in pastures under moderate stocking rates, and beta diversity among plant functional groups was greatest in pastures stocked moderately. Together these results suggest that low temporal variability in forage availability is associated with diversity-stability mechanisms that underlie ecosystem function. At the pasture-level, moderate stocking rates enhance plant group diversity and forage stability in southern Iowa grazing land, which might help livestock producers mitigate livestock productivity loss caused by climatic variability.