Analyses of rates of change in fossil-pollen data from eastern North America reveal that many sites experienced major changes 10,000-14,000 years ago during the last deglaciation and again during the last 1000 years. The major objective of the proposed research is to determine the timing, magnitude, and geographic patterns of the changes in climate and vegetation during the past 3000 years in eastern North America and during the past 14,000 years in Sweden. High-frequency pollen data from an array of sites across eastern North America will be used to analyze in detail the apparently rapid changes occurring during the past millennium and to sort out the climatic and post- Columbian anthropogenic causes. Data from 40 late-glacial sites in southern Sweden will be used to compare the temporal structure of the Scandinavian late-glacial with that of North America. Rates of vegetation change attributable to agriculture and other human activities (as opposed to climatic influences) will be evaluated by contrasting Swedish sites from areas having intensive human impact iwth those from marginal areas receiving little impact. This research will establish the degree to which rapid vegetation changes in eastern North America and Europe are synchronous and will thus identify probable times of major rapid changes in atmospheric circulation. The results will also reveal the degree to which recent vegetation is transitory and to which presettlement vegetation in North America justifiably serves as a steady-state baseline for modern studies.
