Academic journal article The American Midland Naturalist

Combustion Characteristics of Bison (Bison Bison) Fecal Pats Ignited by Grassland Fires

Academic journal article The American Midland Naturalist

Combustion Characteristics of Bison (Bison Bison) Fecal Pats Ignited by Grassland Fires

Article excerpt

ABSTRACT.-We quantified the combustion characteristics of bison fecal pats following three prescribed grassland fires conducted during three different seasons on an Oklahoma tallgrass prairie. We compared heat per unit area, rate of energy consumption and duration of combustion of the burning fecal pats with fireline intensity, reaction intensity and heat per unit area of the fires. Environmental conditions at the time of burning determined the intensity of the fire in the grassland fuels. However, we found no correlation between grassland fire behavior and fecal pat combustion characteristics, suggesting that grassland fuels and fecal pats respond differently to several environmental factors. The heat released per unit area of fecal pat was extreme in each fire. The results suggest the flux of heat created by combusting bison fecal pats may potentially alter patterns of soil resources. If so, this should contribute to species richness and spatial heterogeneity, in tallgrass prairie in a manner similar to other small-scale disturbances.


The prairies of Central North America were shaped by fire and grazing by large herds of American bison (Bison bison) (England and DeVos, 1969; Axelrod, 1985). The influence on prairie composition of these large-scale (>1-ha) disturbance events has been well documented (Anderson, 1982; Wright and Bailey, 1982; Gibson, 1989; Glenn et al., 1992; Vinton et al., 1993). Also important are the numerous small-scale (<2-m2) disturbances that can increase the biodiversity and spatial patterning of plant communities (Collins and Glenn, 1988; Coffin and Lauenroth, 1989; Steuter et al., 1995).

Disturbances to prairie have been examined in terms of disturbance frequency, fire intensity, fuel loading, fuel type, bison grazing pattern and bison stocking rate (Bragg, 1982; Engle et al., 1989; Shaw and Carter, 1990; Bidwell and Engle, 1991; Fahnestock and Knapp, 1993). Differences and interactions among disturbances of varying spatial scale have also been studied (Coppock et al., 1983; Coppock and Detling, 1986; Coffin and Lauenroth, 1988; Biondini et al., 1989; Gibson et al., 1993). The bison fecal pat, in particular the energy released during combustion of the fecal pat when a grassland is burned, is a potential smallscale disturbance that could influence spatial patterning of soil resources and plant species in grasslands.

Considering the abundance of bison and the prevalence of fire in the historical landscapes of Central North America, a bison fecal pat-fire interaction may be an important aspect of disturbance ecology in prairies. Cattle fecal pats function as small-scale disturbances that alter composition and growth of seeded grasslands (Norman and Green, 1958; MacDiarmid and Watkin, 1971; Castle and MacDaid, 1972; Parish and Turkington, 1990). Cattle fecal pats are also important in the practice of prescribed burning. Cattle fecal pats ignite easily under hot dry conditions and can burn with sufficient intensity to start spot fires (Bunting and Wright, 1974). These studies suggest bison fecal pats may function as intense small-scale disturbances when combusted in grassland fires. Our primary objective was to quantify the combustion characteristics of bison fecal pats during three prescribed burns on The Nature Conservancy's Tallgrass Prairie where bison grazing and burning operate on the same landscape. Our secondary objectives were to determine if combustion characteristics of fecal pats differed among prairie fires and to determine if fecal pat combustion characteristics were associated with behavior of the prairie fires.


Study site.-We collected our data on The Nature Conservancy's Tallgrass Prairie Preserve, located in the Osage Hills of northeastern Oklahoma (3649'N, 9623'W) (Hamilton, 1996). All data were collected within a 2250 ha bison enclosure. A herd of about 450 bison of mixed sex and age inhabited the enclosure since 1993. …

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