Late Miocene forests were 90% oak, pine, and hickory

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samson'sseed
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Joined: Sat Oct 29, 2011 9:02 am

Late Miocene forests were 90% oak, pine, and hickory

Post by samson'sseed » Wed Dec 05, 2012 4:38 pm

The Gray Fossil Site in Washington County, Tennessee has yielded over 15,000 vertebrate fossils, but also plant fossils and pollen. They date to between 7 million to 4.5 million years.

A study of the pollen found that the forest was 90% oak, hickory, and pine, just like today.

http://www.sciencedirect.com/science/ar ... 6712000772

The climate was much different, however. There were no frosts or cold winter season. Instead, there was a monsoon like wet season and a droughtlike summer season.

I think many of the oaks and pines must have been of different species than those of today. However, the state of Tennessee website has a slide show of fossils from the site, including leaf impressions.

I recognized post oak and southern red oak. I think that, although these resemble modern species in appearance, they were adapted to a totally different climate. They might not have evolved frost tolerance yet.

wodewose
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Joined: Fri Jan 26, 2018 3:30 am

Re: Late Miocene forests were 90% oak, pine, and hickory

Post by wodewose » Wed Jan 31, 2018 1:24 am

This is interesting. I'm imaging oaks and hickories were being taken over at this time by pines, which are evergreen. The deciduous leaf habit only makes sense in places with winter frosts -- absent frosts, and with a dry season and fire danger oaks and hickories would be expected to persist, but I would guess below replacement level in the face of pine competitiveness. Recent papers on the oak colonization of North America reveal that they evolved in the north, near the Arctic circle where the deciduous habit was a response to lack of winter sunlight. Then they migrated southward on both sides of the Rockies to fill the continent. Of course 33 million years ago the climate was different from 7-4.5 million years ago.
(https://markgelbart.wordpress.com/2017/ ... h-america/)

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