Age Structure of Trees in Thorn Creek Woods

Diameter distributions and age-size regressions are presented for 11 tree species from Thorn Creek Woods, Will County, Illinois. Diameter distributions showed a good fit to the negative power model of survivorship. Nevertheless, 7 of the 11 species showed the \u27gap-bulge pattern, with fewer than expected numbers in intermediate size classes. Although age-size regressions were generally significant, the scatter diagrams for most species showed clustering into two age groups undetected by regression analysis. The juxtaposition of these results suggests the presence of two cohorts on the site; one of post-settlement origin (after 1835), the other emerging after the decline of agriculture (post-1930)