“…Johnson- Groh (1983Groh ( , 1985 described central Iowa woodland communities in much more quantitative terms based on analysis of permanent plot data collected at Ledges State Park (Boone County). She established 54 rectangular permanent plots (0.1 hectare, 20 m X 50 m) throughout the park at sites chosen to represent all aspects, slope levels, slope inclinations and various degrees of disturbance.…”