Pollen evidence for the protohistoric development of the “big woods” in Minnesota (U.S.A.)

Abstract

When the presettlement deciduous forest, as described from land-survey notes of 1854–1860, is compared with relict forest stands of today, it is clear that mesic succession has taken place. The “Big Woods”, dominated by Acer and Tilia, has developed from a forest dominated by Ulmus and Quercus with some Tilia and Acer. Two pollen diagrams spanning the past 1,000 years show that this succession was initiated several hundred years before settlement. Three pollen diagrams from the adjacent oak forest suggest a concurrent succession from Quercus savanna, as well as a later increase in mesic elements at the time of settlement. An area that was oak barrens (a type of Quercus savanna) at the time of settlement, now has relict stands of oak forest; the two pollen diagrams from this area suggest the formation of oak forest since settlement. The mesic successions are probably a culmination of a long-term change toward a cooler and moister climate, but a postulated decrease in Indian populations and fires after European contact about 1650 and before settlement could have accelerated the vegetation successions.