• Faison E
  • et al.
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Abstract. The pre-historical vegetation structure in temperate forest regions is much
debated among European and North American ecologists and conservationists. Frans Vera’s
recent hypothesis that large mammals created mosaics of forest and openland vegetation in
both regions throughout the Holocene has been particularly controversial and has provoked
new approaches to conservation management. Thirty years earlier, American paleoecologists
Herb Wright and Margaret Davis debated whether abundant ragweed pollen at Rogers Lake,
Connecticut at 9500 yr BP signified local forest openings or long-distance transport of pollen
from Midwestern prairies. Using new pollen records from Harvard Forest and the North
American Pollen Database, we address this question and offer insights to the openland
discussion. Ragweed and other forbs exceed 3.5% at five sites in a restricted area of southern
New England between 10 100 and 7700 yr BP. Strong evidence suggests this pollen originated
from the landscapes surrounding these sites (supporting Davis), as ragweed pollen percentages
do not increase with longitude from New England to the Midwest. Ragweed pollen
percentages are also unrelated to basin size and therefore unrelated to the proportion of
extraregional pollen in New England. High forbs values were associated with increases in oak,
decreases in white pine, and relatively high charcoal values. Modern pollen records with
similar forb and tree percentages occur along the Prairie Peninsula region of the Upper
Midwest. However, the closest analogue to the southern New England early Holocene
assemblages comes from Massachusetts’ Walden Pond in the early 18th century. These results
and the affiliation of ragweed for open, disturbed habitats suggest that oak–pine forests with
large openings persisted for over 2000 years due to dry conditions and perhaps increased fire
frequency. This conclusion is corroborated by independent lake level and climate
reconstructions. Because these early Holocene openlands have no detectable analogue in
New England for the past 7000 years before European settlement, we suggest that all
important openlands today are almost exclusively a legacy of Colonial agriculture and should
be managed accordingly. Nonetheless, our results may have implications for forest dynamics
accompanying projected climate change to more arid conditions in New England over the next

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  • E.K. Faison

  • et al.

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