Re: New ref

[Jeff Hecht <jhecht@WORLD.STD.COM>]

>
>
>Abstract: The T-J boundary marks a major faunal mass extinction, but
> records of accompanying environmental changes are limited. Paleobotanical
> evidence indicates a fourfold increase in atmospheric carbon  dioxide
> concentration and suggests an associated 3 to 4 degree "greenhouse" warming
>
>
> Amazing! I know nothing about botany, let alone palaeobotany, but could
>anyone give me a brief explanation on how they would be able to find out
>something like that from (I presume it was) fossilised plants? I had
>understood that physiologically speaking, it was difficult to really find
>anything out from fossils, especially plants.
>
The number of stomata on leaves depends on carbon dioxide levels; the more
CO2, the fewer stomata. They found a series of well-preserved leaf deposits
that spanned the boundary and counted stomata, finding a dramatic decrease.
They also noted a dramatic change in leaves across the boundary, shifting
from large leaves to smaller ones; smaller ones could survive in hotter
weather. It's a nice little story, well described in Science (and coming
out in this week's New Scientist as well; I'm not sure if it's on the web
site, though).


Jeff Hecht     Boston Correspondent    New Scientist magazine
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see New Scientist on the Web: http://www.newscientist.com/