The effect of a prescribed burn on a chestnut oak woodland in the Hoosier National Forest : an honors thesis (HONRS 499)

Abstract

The objective of this study was to determine the effects of a prescribed fire on the understory vegetation of a chestnut oak woodland. A prescribed surface burn was done in half of the study area in March 1993. This study compares the understory vegetation of this burned area with that in an adjacent, similar but unburned area. Mean percent cover of herbaceous and low shrub vegetation was 78.5% in the burned area and 24.4% in the unburned area. Percent of the ground surface with exposed mineral soil was 45.1% in the burned area and 1.0% in the unburned area. Eight species of understory plants were found only in the burned area; only one species was found only in the unburned area. The mean Shannon-Wiener Diversity Index for plots in the burned area was higher than for plots in the unburned area (2.842 vs. 2.592), indicating an increase in understory plant diversity after the fire. One likely cause for the increase in herbaceous cover and diversity is fire damage to overstory tree crowns, which allows more light to penetrate to the forest floor. The areas selected for this study were south-facing, exposed slopes where the fire burned most intensely, causing some damage to the crowns of overstory trees. Vigorous stump sprouting was observed at the root collars of most fire killed shrubs and trees. However, most of these sprouts were of the very tree species that the fire was intended to reduce (red maple, sassafras, blackgum). Repeated prescribed fires will be required to diminish the cover of these tree species, which inhibit the growth and diversity of the understory herb and shrub community by casting a dense shade.