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ABSTRACT
Cross-sections of 36 post oaks (Quercus stellata Wang.) were examined to determine the fire history of a post oak woodland in Hamilton County, Illinois. The 226-year tree ring record contained three distinct periods; a fire era from 1776 to 1850 having a mean fire return interval of 1.97 years, a fire-free period from 1851 to1884, and a second fire era from 1885 to 1996 having a mean fire return interval of 1.44 years. The fire-free interval corresponds with the rapid settlement of Hamilton County during 1850-85. The fires between 1770 and 1850 are considered landscape fires associated with Native Americans and/or early European settlers, while those between 1885 and 1996 are thought to be due to burning of local woodlands, a practice that became increasingly less common in the late 20th century. Three post oak cohorts were identified, including 211-224 year-old (217-year mean), 137-151 year-old (144-year mean), and 104-115 year-old (105-year mean) age classes. Post oak recruitment ended and fire sensitive hickories (Carya ovata and C. tomentosa), black cherry (Prunus serotina), sassafras (Sassafras albidum), and black oak (Quercus velutina) now dominate the seedling and sapling layers of the woodland.
INTRODUCTION Few data are available on the historic occurrence of fire in Illinois, and the prairie-forest ecotone region of the Midwest in general. Robertson and Heikens (1994) examined 299 cross sections from trees in barren communities in southern Illinois and concluded that the historic fire record could not be determined because none of the trees predated European settlement. Guyette (1982) examined the fire history of Big River State Forest in Henderson County, but tree ages at this site seldom exceeded 100 years. The two earliest fire records from Illinois, reported by Ebinger and McClain (1991), dated two scars from cross sections of two old-growth white oaks Quercus alba L. in Edgar County to the 1670s. However, this small sample prevented effective crossdating and the development of fire chronologies and frequencies.
The potential for developing an extensive fire history for Illinois was realized when numerous fire scars were observed on stumps of a recently harvested old-growth post oak community in northern Hamilton County, Illinois in the fall of 1996. The site was selected for study to determine the frequency of fire in a post oak...