Effect of Prescribed Burning at Different Fuel Moisture Levels on Grasslands in Wind Cave National Park

Abstract

The study was designed to determine whether different fuel and soil moisture levels at time of ignition would alter the response of key grass species to prescribed burning. Grasslands occupy approximately 75% of the area of Wind Cave National Park (WCNP); the remainder is dominated by ponderosa pine (Pinus ponderosa), according to Lovass (1973). The Soil Conservation Service (1969) classed only about 17% of the Park area as woodland. Nearly all grassland adjacent to woodland has been invaded by ponderosa pine. Almost without exception, pine invades the little bluestem - big bluestem (Schizachyrium scorparium - Andropogon gerardi) community, but not the wheatgrass - needle-grass - grama (Andropogon - Stipa- Bouteloua) community. While these two communities are frequently interspersed, the bluestem community probably occupies the largest percentage of the total grassland area. The general relationships between fuel moisture content and fire spread (or ease of control) are well known. However, relationships between fuel and surface soil moisture content and responses of plant species to burning are not well documented. Since the key grass species of the bluestem community are major dominants throughout the Park, that community was selected for the study. Examined were the effects of three fuel moisture levels (dry, medium and wet) at ignition on postburn species composition, cover, height, weight, soil moisture and soil chemistry. The design also included an unburned (control) treatment.