$title="Introduction - Origin of the Prairie 2"; include "/local/php/ismsite/midewin/header.php"; ?>
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Gleason (1923) suggested that the prairies developed during an
early post-glacial time of greater aridity. We know from
fossil-pollen data that prairie began to develop in the western
part of the Prairie Peninsula as early as 10,000 years ago but did
not reach its full extent in the eastern part of the Peninsula
until about 6000 years ago.
Analyses of preserved pollen from the eastern part of the Prairie Peninsula show that some prairie developed in the region about 9000 years ago, but the major development of the modern prairie occurred about 5000 to 6000 years ago, when elm and other trees became much more restricted. Some sites indicate that conditions became somewhat wetter after 3000 years ago, with an expansion of prairie oak groves.
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