Response of big bluestem (Andropogon gerardii Vitman) to specific date of spring burning.

The tallgrass prairie of central North America has been described as a fire-derived and fire-maintained ecosystem (Stuart 1951) in which fires occurred intermittently and throughout the year (Jackson 1965). Because of the importance of fire to this ecosystem, its effects have been widely studied and summarized in reviews by Ehrenreich (1959), Daubenmire (1968), Vogl (1974), and Hulbert (1986). The effect of burning during different seasons has been studied with varying results. Winter burns reduce herbage production of warm-season dominants and shift vegetational composition by differentially favoring cool-season species (e.g. Towne and Owensby 1984). Mid-to late-season fires also damaged the C4 dominants. At this time, the species are growing rapidly, and the meristems are evaluated above the soil surface. Thus, they are subject to greater injury from burning. During summer and fall, the plants may also be stressed by low soil moisture (Risser et al. 1981). Late summer fires have been shown to cause shifts in community composition from warm-season dominants (Ewing and Engle 1988)