Vegetation Change After Thirteen Years of Fire Management of a Northeastern Illinois Oak Woodland
DescriptionReport to the Chicago Wilderness.
AbstractLandscape fire processes patterned midwestern vegetation at the time of European settlement,
producing mosaics of oak-dominated savannas and woodlands throughout the prairie / forest border of
northeastern Illinois and southern Wisconsin (Anderson 1991, Leitner et al. 1991, Bowles et al. 1994).
Because of the importance of fire in maintaining oak forests (Abrams 1992), fire-protection since
European settlement is thought to have been a critical factor leading to successional changes and loss of
floristic biodiversity caused by a decline in understory plants (McIntosh 1957, Curtis 1959, Wilhelm
1991, Bowles & McBride 1996, Anderson & Bowles 1999). Prescribed fire is used as a management tool
to restore Midwest oak savannas and woodlands by counteracting this tendency (Apfelbaum & Haney
1991). However, very little information is available on the long-term effects of fire, especially on how
repeated burning will effect ground-layer composition. As a consequence, prescribed fire management is
subject to continuous debate (e. g. Mendelson 1998).
Prescribed burning increased richness of prairie species in a Minnesota sand savanna (White
1983, Tester 1989), and ground-layer species richness in a southern Wisconsin oak forest (Kline &
McClintock 1994). Schwartz and Heim (1996) found that a single March fire in a degraded oak forest
reduced woody stems, but did not affect herbaceous species. However, a May fire in the same woods
reduced herb density over three years. Luken & Shea (2000) found five years of repeated burning of an
upland maple-ash forest caused a reduction of small woody stems, but little change in ground-layer
Results such as these have not clarified assumptions that prescribed fire can restore or increase
species richness and diversity in midwestern forests or woodlands, nor has it illustrated causal factors.
Further, a lack of solid baseline data on species composition and the structure of the original oak
woodlands makes it difficult to set quantitative restoration or management goals. To help address these
issues, we established permanent sampling transects in 1986 in pre-designated “burn” and “unburn”
(control) management units of oak woodland at Reed-Turner Woodland Nature Preserve, Lake County,
Illinois. We sought to determine whether richness, composition, and structure of ground-layer vegetation
were enhanced by repeated, long-term, prescribed burning in comparison to areas that were not been
burned since burning was implemented in 1987.