General Land Office (GLO) survey notes (1840–1856), current land cover generated from Landsat TM Imagery (1991) and the Forest Inventory and Analysis plots (1991–1992, US Forest Service) were used to examine changes in forests of the Luce District in Upper Michigan over the past 150 y. Historical changes in two subdistricts, Grand Marais and Seney, were also analyzed. Interpretation of GLO notes showed that the presettlement landscape was a mixed conifer matrix (39% of total area), interspersed primarily with northern hardwoods (29%), wetlands (14%) and fire-susceptible pinelands (13%). Estimates of pre-European settlement stand density ranged from 81 trees/ha in open lands to 408 trees/ha in northern white cedar stands (Thuja occidentalis), and estimates of basal area ranged from 3.5 m2/ha in wetlands to 27.7 m2/ha in mixed hardwood/conifer forests. Notable changes in species composition over the last 150 y are the increase of red maple (Acer rubrum; 14%) and the decline of tamarack (Larix laricina; −11%), hemlock (Tsuga canadensis; −7%), white pine (Pinus strobus; −6%), beech (Fagus grandifolia; −5%) and yellow birch (Betula alleghaniensis; −5%). Contrasts between the two subdistricts, Grand Marais and Seney, reflect the influence of the integration of climate, physiography and disturbance regime. Overall presettlement vs. present-day tree diameter distributions differed between the two time periods. Differences in the diameter distributions among individual tree species are related to their growth rates and life expectancies. The diameter distributions of short-lived species are similar between the two time periods. Most species have diameter distributions with more small trees today than in presettlement forests, especially long-lived taxa such as hemlock and white pine.
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Vol. 143 • No. 1