In two or three circular 0.1 ha plots within each stand (with the exception of the severe disturbance stand burned in 1998, which contains two rectangular plots of 0.14 and 0.06 ha), every tree with a diameter at breast height (BH = 1.37 m) 8.0 cm or greater was identified by species, designated by crown class (dominant, codominant, overtopped, or broken), and measured for DBH. The distance and azimuth from plot center was also recorded for each tree. The rectangular plots that experienced the 1998 burn were divided into quadrats, and the distance and azimuth measurements for each quadrat were taken from the easternmost post on the north side of the quadrat.
Aboveground biomass (Ma) was determined in each plot from DBH (d) measurements using allometric equations.
Ma = a * d^b [1]
where species-specific coefficients a and b were determined from reports published on the Great Lakes region and developed from data collected at UMBS (Gough et al. 2008). Broken dead trees were treated as cylinders using an average density calculated from site-level Q. rubra, B. papyrifera, and P. grandidentata class one and two coarse woody debris data (Hunter et al. 1999). Total aboveground biomass per hectare was calculated for each plot, and regressions of biomass per hectare over stand age were generated for the moderate and severely disturbed chronosequences.