A sequence of 49 small stands of increasing mean diameter from Menominee Forest in northern Wisconsin illustrates the development of stand structure. Density-diameter distributions of natural old-growth stands of small area or uniform structure are of a rotated sigmoid form rather than the previously reported negative exponential form. The negative exponential form seems characteristic of large forest tracts having localized patches of even-aged trees. In smaller stands where interactions between canopy and understory are important, the typical stand structure curve shows an understory phase of slow growth and high mortality, a vigorous canopy phase of relatively rapid growth and low mortality, and an older canopy phase of reduced growth and increasing mortality
