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RE: Extinction scenarios




-----Original Message-----
From:   John Bois [SMTP:jbois@umd5.umd.edu]
Sent:   Tuesday, August 18, 1998 7:20 PM
To:     Augustus T. White
Cc:     'Dinogeorge@aol.com'; "jwoolf@erinet.com"@usc.edu; dinosaur@usc.edu
Subject:        RE: Extinction scenarios


<<Very good.  But can you give us a more specific idea of what kind of
ecological succession you could be meaning.  Otherwise you just seem to be
heading toward the: "we don't know how it happened but there was a lot of
ecological turmoil caused, probably, by a variety of forces, biological
and physical (including the bolide) having unspecified effects."  Which is
to say, away from the bolide-as-sufficient idea!>>

Given my very modest credentials in ecology, much less paleoecology, the 
answer has to be a simple "no, I can't."  That's why I stated that I didn't 
know if it could be turned into a testable hypothesis.  I can speculate, 
but my speculation may be worse than random chance in terms of its 
relationship to reality.  I'll do so anyway.

Lets picture a landscape ten or twenty years after an imaginary KT event in 
which almost everything was killed unselectively, but nothing became 
extinct.  With most vegetation killed off initially, and nothing to hold it 
in place, the soil has sorted by elevation, according to particle size. 
 Hills are largely bare rock.  Depressions have collected fine particles 
and are beginning to grow sizeable tangles of brush.  There are no large 
trees, although some are growing back.  In the main these are fast-growing 
species with shallow root systems, easilly knocked over by storm or 
frequent flash floods.  Still, there is a small forest of sorts growing 
around the rim of depressions.  With a fair amount of still water, there 
are clouds of insects in the brush.  Many amphibian and freshwater 
populations are exploding as a result of the good food supply and cover. 
 Their predators, small mammals and crocs, are beginning to recover for the 
same reasons, although at this stage, the mammals aren't perhaps doing as 
well as the crocs.  There are some small theropods surviving in the belt at 
the margins.  They aren't doing well.  Their habitat is somewhat unstable. 
 Their prey sticks close to the thick brush and muck where bipedal dinos 
aren't safe.  On the other side are rocky, unstable surfaces, equally 
unsuited to this body plan.  Originally, there were birds nesting among 
those rocks, but they have learned to leave their young in more protected 
areas.

The savannah and forest biomes whre their larger cousins used to hang out 
have been decimated.  There's a lot of howling desert out there.  Ground 
plants are beginning to recover, but there isn't the even distribution of 
plant biomass that used to support herd animals.  Gone with the herd 
animals are, of course, the top predators.  Life is more concentrated in 
smaller patches.  Some solitary ankylosaurs graze along riverene 
greenbelts, but floods and mammals are making egg-laying hazardous for 
non-flying species in the restricted space of lake and river-margin biomes.

Enough?

  --Toby White