During the last ten years, there have been several kinds of major disturbances that have occurred in oak, aspen, and northern hardwood stands throughout the lower peninsula of Michigan. Defoliation by the gypsy moth became a major disturbance in Michigan forests during the 1980’s and remains a problem at present. In addition to insect damage, Michigan’s hardwood forests also face stress from severe droughts, such as the hundred year drought event of 1988. Frost stress plays a role as well, particularly in low-lying areas. Frost stress can occur on a yearly basis at some locations due to physiographic factors; in addition, severe frost events can take place on a regionwide basis, such as the severe frost events in the spring of 1992. Between 1991 and 1993, we established a system of plots (the Michigan Impact Monitoring System, or MIMS) to monitor stress factors and forest conditions throughout the hardwood forests of Michigan’s lower peninsula. The objectives of the study are to: 1) establish an impact plot system in Michigan to monitor forest conditions, 2) survey regeneration in oak, aspen, and northern hardwood stands, 3) survey and monitor, over time, tree mortality and conditions of oak, aspen, and northern hardwoods stands, 4) develop a multifactor ecological site classification system for plots in MIMS, 5) determine relationships among tree mortality, stress history, and stand, site, and soil variables, 6) determine the effects of silvicultural treatments on stand conditions, 7) determine the efficacy of various types of aerial photography for monitoring forest conditions, and 8) develop and validate a rating system that can be used by managers to rate potentially vulnerable stands. The MIMS system consists of 566 plots located in 283 stands throughout 33 counties in lower Michigan. Of these, 197 are oak stands, 48 are aspen stands, and 38 are northern hardwood stands. In each study stand, we established two 30 x 30 m plots in which we record data at the level of the individual tree for all trees greater than 5.0 cm DBH. Data collected include tree species, DBH, crown position, and tree condition (live or dead). Additionally, intensive data collection is performed for the first 15-20 trees/plot to obtain information on tree height, live crown height, crown vigor, and current defoliation. Two 9 x 9 m subplots are also established within each of the large plots. In these subplots, we tallied all woody regeneration in 2 size classes (0-2.5 cm DBH, 2.6-5.0 cm DBH) and 5 species classes (maples, oaks, aspen, conifers, other hardwoods). Results to date have shown that, overall, the health of Michigan’s forests is quite good (e.g., oak forest type: 124 ft2/acre of basal area and 4.8% dead; aspen forest type: 142 ft2/acre and 4.4% dead; northern hardwood forest type: 150 ft2/acre and 2.4% dead). Vigor of living trees is also good in general throughout all forest types. However, forest conditions do exhibit considerable differences among ecosystem units, forest stands, tree species, and crown classes within each of the forest types. For example, in the oak forest type the percent of standing overstory trees that are dead ranges from 0-50% among different ecosystem units. Variation in mortality among species in the oak forest type ranges from 19% of standing northern pin oak stems dead, 11% of standing white oak stems dead, 7% of standing red oak stems dead, to 5% of standing red maple stems dead. In all three forest types, the dominant and codominant crown classes have relatively few dead stems, with the exception of dominant and codominant northern pin oak trees in dry oak ecosystems. However, tree mortality is generally much higher in the intermediate and suppressed crown classes of each forest type. Both the forest conditions and forest composition show marked differences among counties in Michigan.