Production on burned and unburned sand prairies during drought and non-drought years

Abstract

Biomass production was determined on burned and unburned sand prairie sites in Illinois during the 1986–89 growing seasons. Severe droughts characterized the 1988 and 1989 growing seasons with precipitation being at least 50% less in these two years than in 1985 and 1986. During the growing season following a fire, in drought and non-drought years, burned sites had higher total green biomass (all species), little bluestem (Schizachyrium scoparium) root and shoot biomass, and total grass and forb biomass production than the unburned sites. In 1988 and 1989, production on all sites was frequently significantly lower each month than it was in 1986 or 1987. The differences in productivity between burn and unburned sites were less pronounced during the drought years (1988–1989) than during the non-drought years (1986–87). Grass productivity (all species) declined considerably during drought years. In contrast, forb productivity did not vary significantly among years. Despite the drought, productivity of all species and little bluestem (root and shoot combined) was best predicted by the burn condition of the sites. Unlike many studies where drought alone can have significant effects on productivity, this study shows that on sand prairies the burn condition of sites, or burning regimes, and associated influences, can have a greater substantial impact on productivity than drought. Moisture deficits due to drought may, however, have longer term effects than those detected during the span of this study.