EFFECTS OF A PRESCRIBED FIRE ON DEGRADED FOREST VEGETATION

The response of the understory herbaceous flora to fire management was studied in a degraded woodland in northern Illinois. The site contain s a rapidly expanding population of Alliaria petiolata a non-indigenou s plant that is highly invasive in forests. Three treatment units (Mar ch fire, May fire, and unburned) were sampled in 1991, prior to fire t reatments. Following prescribed fire, plots were sampled annually from 1992 to 1994, inclusive, to track the response of the vegetation to t he fire treatment. The purpose of the experiment was to assess the imp act of fire on (1) A. petiolata populations, (2) the native herbaceous flora, and (3) shrubs and saplings. The initial impact of fire on A. petiolata, understory forbs, shrubs, and saplings was strongly negativ e in the growing season burn unit and moderate in the dormant season b urn unit. After three years, A. petiolata had not recovered to preburn densities in the growing season burn unit. Likewise, densities and ri chness of native herbaceous species remained below preburn values in t he growing season burn unit after three years. Dormant season and grow ing season burns equally and strongly reduced shrub and sapling densit ies relative to the control unit.