In recent years there have been many studies of biomass and primary production in forest ecosystems, but because forest ecosystems are long-lived, and because there are relatively few data sets from permanent sample plots or artificial chronosequences documenting changes in individual forest stands, few estimates have been made of change in biomass and net primary production over long periods in the life of a forest. An opportunity to study such changes and to test the various hypotheses concerning changes in biomass and net primary production during succession is available at the University of Michigan Biological Station (UMBS) in west central Cheboygan County, Michigan. Here bigtooth aspen (Populus grandidentata) forests now occur on soils previously occupied by pine, and ecological studies have been under way since 1910. Considerable data and several permanent sample plots established by F. C. Gates exist documenting changes in the biota of the region as it recovered from extensive logging and fire in the early 1900s. During the summers of 1967-1969 and 1971 I carried out a program of research involving (1) dimension analysis of the canopy species of the bigtooth aspen ecosystem; (2) re-analysis of Gates’ permanent and experimental burn plots; and (3) analysis of other sample plots in mature aspen stands. These data, together with remeasurement of the plots in the summers of 1973 and 1979, were combined to yield estimates of changes in biomass and net primary production over the first 70 years of succession in bigtooth aspen stands.