Composition and Structure of an Old-Growth Forest Remnant in Unglaciated Southwestern Illinois

Abstract

All stems 2.6 inches (6.6 cm), or greater, in diam breast height (dbh) were tallied in an 18-acre (7.2 ha) forest on loessal soils of the Ozark Hills in Union Co., Ill. Understory and ground vegetation were sampled in 0.01and 0.001-acre (4 sq m) transects and quadrats. Stand density was 221 stems per acre and basal area was 130 sq ft. Sugar maple (Acer saccharum) was the leading species based on importance values of 38 species. The canopy strata included shagbark hickory (Carya ovata), black oak (Quercus velutina), northern red oak (Q. rubra), sugar maple and white oak (Q. alba). Sugar maple and shagbark hickory increased substantially in the canopy during an 11-year period from 1956 to 1967, while northern red oak and black oak decreased in importance value. The increased importance of sugar maple in the stand was attributed to absence of major disturbance, climatic and soil changes in the past century, related to increased precipitation during much of the period, and selective cutting. The stand was classified as western mesophytic (Braun, 1950).