Long-term Effects of Annual Burning at Dif- ferent Dates in Ungrazed Kansas Tallgrass Prairie - GENE TOWNE AND CLENTON OWENSBY

Ungrazed tallgrass prairie plots in the Kansas Flint Hills have been burned annually at 4 different dates since 1928. Time of burning markedly altered the physiognomy and was the crucial factor effecting vegetation change. Late-spring burning, coinciding with emergence of the warm-season perennial grasses, increased grass production and favored Andropogon gerardii and Sorghastrum nutans. Burning in winter, early-spring, or mid-spring reduced herbage production and shifted vegetational composition by differentially favoring other species. Andropogon scoparius increased with midand early-spring burning, while perennial forbs and sedges increased with early-spring and winter burning. Amorpha canescens was favored by all burning treatments. Mulch buildup in unburned, undisturbed plots increased Poa pratensis and tree species and eventually reduced grass production. The long-term effects of annual late-spring burning, even in dry years, was not detrimental to herbage production, species composition, or total basal cover in tallgrass prairie. Tallgrass prairie is fire-derived and fire-maintained (Stewart 1951). Historically, fires were intermittent and occurred at nearly any time of the year (Jackson 1965). In the 1880’s, cattlemen observed that transient steers gained more weight on burned than on unburned range, and as a result, grazing leases later mandated annual burning (Kollmorgen and Simonett 1965). Time of burning, however, was of little concern, and most pastures were burned in January or February to stimulate earlier greenup. Although voluminous literature exists on vegetational effects from fire, few studies have acknowledged the importance of time of burning. Aldous (1934) initiated preliminary research on burning ungrazed tallgrass prairie at different dates. Subsequent reports on herbage production (McMurphy and Anderson 1963) and botanical composition (McMurphy and Anderson 1965) were nonreplicated, short-term studies in which the unburned control was mowed and raked annually, and included data from years when the plots were not burned. This paper compiles earlier research and adds recent data from undisturbed control plots to evaluate the importance of time of burning on herbage production and species composition in ungrazed tallgrass prairie over the past 56 years. Study Area and Methods The experimental site is located on a level ridge top in the Kansas Flint Hills north of Manhattan. From the early 1900’s, the area had been moderately grazed by cattle and routinely burned in late winter. Soil at the site is a loessial-derived Smolan silt loam classified as a Pachic Argiustoll. It has a dark-gray surface layer about 20 cm thick overlying a deep silty clay loam subsoil. Vegetation at the beginning of the study was predominantly little bluestem Authors are research assistant and range research scientist, Department of Agronomv. Kansas State Universitv. Manhattan 66506. The voluntarv efforts of Doreen ToLne in manuscript word p&essing are greatly appreciated. . Additional graphs of yearly fluctuations for the major plant species under different burning treatments are available from the authors on request. This report is Contribution No. 83-135-J, Department of Agronomy. Kansas Agricultural Experiment Station, Manhattan 66506. Manuscript accepted December 29, 1983. (Andropogon scoparius Michx.)‘, with prairie junegrass [Koeleriu pyrumidutu (Lam.) Beauv.], big bluestem (A. gerurdii Vitman), and indiangrass [Sorghustrum nutuns (L.) Nash] also prevalent (Table I). Mean annual precipitation for Manhattan since 1928 is Table 1. Percent botanical composition based on actual stem numbers in 1926 on Kansas Flint Hills study site before date of burning treatments began.