Moderate Grazer Density Stabilizes Forage Availability More Than Patch Burning in Low-Stature Grassland

Edward J. Raynor, Devan Allen McGranahan, James R. Miller, Diane M. Debinski, Walter H. Schacht and David M. Engle
Additional contact information
Edward J. Raynor: USDA-Agricultural Research Service, Rangeland Resources & Systems Research Unit, Fort Collins, CO 80526, USA
Devan Allen McGranahan: Environmental & Conservation Sciences, North Dakota State University, Fargo, ND 58105, USA
James R. Miller: Natural Resources & Environmental Sciences, University of Illinois, Urbana, IL 61820, USA
Diane M. Debinski: Department of Ecology, Montana State University, Bozeman, MT 59717, USA
Walter H. Schacht: Center for Grassland Studies, University of Nebraska-Lincoln, Lincoln, NE 68588, USA
David M. Engle: Natural Resource Ecology & Management, Oklahoma State University, Stillwater, OK 74078, USA

Land, 2021, vol. 10, issue 4, 1-11

Abstract: Spatially patchy fire creates landscape-level diversity that in turn stabilizes several rangeland ecosystem services, including forage production and habitat availability. To enhance biodiversity and livestock production, efforts are underway to restore fire regimes in rangelands throughout the Great Plains. However, invasive species such as tall fescue Schedonorus arundinaceus syn. Festuca arundinacea , initially introduced for forage production, hamper prescribed fire use. Grazer density, or stocking rate, modulates the effect of patchy fire regimes on ecological patterns in invaded, semi-natural rangeland pastures. We compare three diversity–stability responses—temporal variability in aboveground plant biomass, portfolio effects among plant functional groups, and beta diversity in plant functional group composition—in pastures managed with two different fire regimes through three periods of heavy, light, and moderate stocking rate in southern Iowa, USA. Pastures were either burned in patches, with one-third of the pasture burned each year, or completely burned every third year. The period of moderate grazer density had the least temporal variability in aboveground plant biomass, regardless of fire regime. We also found statistical evidence for a portfolio effect under moderate stocking, where diversification of plant communities through varying cover of functional groups can stabilize communities by reducing year-to-year variability. Beta diversity among plant functional groups was greatest during the moderate grazer density period as well. The short stature of tall fescue prevented the patch-burning regime to create contrast in vegetation structure among patches, and there was no difference in any diversity–stability mechanism response across the two different patterns of burning. Although longitudinal, these data suggest that temporal variability in aboveground plant biomass declines with diversity–stability mechanisms that underlie ecosystem function. Our results also support a decades-old principle of range management: moderate grazing intensity enhances diversity and stability, which has been shown to buffer forage shortfalls during drought.

Keywords: diversity–stability; fire–grazing interaction; great plains; temporal variability (search for similar items in EconPapers)
JEL-codes: Q15 Q2 Q24 Q28 Q5 R14 R52 (search for similar items in EconPapers)
Date: 2021
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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