Prescribed Burning in the Loess Hills Mixed Prairie of Southern Nebraska

Abstract

Abused rangelands dominated by introduced cool-season grasses and warm-season shortgrasses are common over much of the Mixed Prairie. Native decreaser species are primarily warm-season grasses and are present at only insignificant levels on abused rangeland in the Loess Hills of southcentral Nebraska. A single, latespring, prescribed fire was evaluated as a method of improvement. The study area consisted of 3 tracts of plots located on Holdrege silt loam soil (Typic Argiustall) with an average annual precipitation of 550 mm. The vegetation on the tracts was in low range condition, with cooland warm-season components being present in varying proportions on all tracts. In general, the dominant cool-season species were Kentucky bluegrass (Poa pratensis) and annual bromes (Bromus spp.), and the dominant warm-season species were blue grama (Bouteloua gracilis) and buffalograss (Buchloe dactyloides). Burning reduced the basal cover and herbage yields of cool-season species. This favored the warm-season component. The increaser short grasses generally exhibited higher herbage yields and basal cover on burned as compared to unburned plots. These results indicate that a single, late-spring, prescribed burn may have a limited potential as a range improvement practice in the Loess Hills of south central Nebraska. The Loess Hills of Southern Nebraska west of 980 30' west longitude were described by Weaver (1965) as Mixed Prairie. The dominant native vegetation was a mixture of primarily warmseason tall, mid, and shortgrasses. Currently, over one-third of the Loess Hills is classified as native range. Due to mismanagement, approximately 60% of this rangeland (1.6 million ha) is in poor to fair range condition (Bose 1977). Improper grazing management has caused a shift in species composition from the native warmseason plant community to a mixture of warm-season shortgrasses, i.e., blue grama (Bouteloua gracilis)' and buffalograss (Buchloe dactyloides), and undesirable cool-season grasses, i.e., Kentucky bluegrass (Poapratensis), Canada bluegrass (Poa compressa), and annual bromes (Bromus spp.). This species composition shift results in a reduction of the quantity and quality of forage produced during the summer months. There are numerous methods of improving rangeland in low condition, but one of the simplest and least expensive practices is prescribed burning. The ability of prescribed fires to selectively suppress or promote particular species depends primarily upon the date of the fire in relation to the phenology of the particular species. As a general rule, those species actively growing when the area is burned are much more susceptible to injury and death than dormant species or those initiating growth (Anderson et al. 1970). Fire severity, which is closely related to fuel loading, size and distribution of fuel, weather, and moisture content of soil and fuel, is also a major factor affecting fire damage to living plants (Wright and Bailey 1982). A late-spring fire has been a particularly effectve Authors are graduate research assistant and professor (range ecology), Department of Agronomy, University of Nebraska, Lincoln 68583. Mr. Schact is currently graduate teaching assistant, Range Science Department, Utah State University, Logan 84322. Published as Paper Number 7087, Journal Series, Nebraska Agricultural Experiment Station. Manuscript accepted March 25, 1984. 'Nomenclature follows Gould and Shaw 1983. method of controlling Kentucky bluegrass (Hensen 1923, Ehrenreich 1959, and Launchbaugh and Owensby 1978), Canada bluegrass (Curtis and Partch 1950), and Japanese brome (Bromus japonicus) (McMurphy and Anderson 1965). In many mesic areas of the Mixed Prairie, prescribed burning has been used to control cool-season grasses without reducing herbage yields or cover of warm-season grasses (Kirsch and Kruse 1972, Gartner and Thompson 1972), although total herbage yield has been reduced the first year following the burn (Dwyer and Pieper 1967). The primary purpose of this study was to determine the potential of a single late-spring prescribed burn in one part of the Mixed Prairie as a means to shift species composition from low yielding warm-season shortgrasses and introduced cool-season grasses to species more indicative of the native Mixed Prairie vegetation, such as big bluestem (Andropogon gerardii), little bluestem (Schizachyrium scoparium), switchgrass (Panicum virgatum), and sideoats grama (Bouteloua curtipendula).