RESPONSE OF CREEPING BLUESTEM TO VARYING MONTH OF BURN AND SOIL-WATER CONDITIONS

Research was designed to determine if Schizachyrium scoparium var. polycladus responses vary with month of burn and soil water conditions during fire. Bluestem was grown in tanks with a 2 x 2 x 3 factorial of month (June or January), soil water (saturated or dry), and defoliation treatments (burn, clip, or none). Tiller density, rhizome mass, and total nonstructural carbohydrates were lower (P<0.05) during the 50 days after burning in June when dry soil (25mm depth) reached 90 degrees C and remained about 50 degrees C for 68 minutes postburn. Reproductive tiller density 94 days after June 1987 burn was not affected by water, but was lower in burn vs. other defoliation treatments. No treatment in January 1988 affected tiller density or rhizome mass in a 50 day postburn period. In September 1988, there were no effects due to month or water, but vegetative tiller density was lower in burn and clip vs. no defoliation, total tiller density was different among all treatments, and reproductive:vegetative tiller density (R:V) ratio was higher in burn vs. clip and no defoliation. In Florida, fire on hot, dry sandy soils in June may have short term negative effects, and fire at either season or soil water level may reduce total tiller density and increase R:V ratio in creeping bluestem for up to 476 days postburn.