[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: flowering plants



>From: carlson@tellabs.com
 > 
 > I guess I will risk "de-lurking" to comment on this. The Morrison
 > is/was a big place. In Montana there is coal deposited during the
 > Morrison. In Wyoming there is lacustrine limestone with Equisetum
 > in it, as well as bits of conifers. Not to mention the Cycadeoid
 > trunks found there. In Colorado there are fern fronds from the
 > Morrison. The coal wasn't deposited under arid conditions, and the
 > Equisetum and the ferns absolutely require water for reproduction.

True enough.  However there is reason the believe that the ferns
provided the ground cover in aras lacking woody plants.  It doesn't
really take *that* much water for ferns to reproduce.

 > So I'd tend to pick a term like 'seasonally-arid' or
 > 'strongly-monsoonal' (implying a big shift in the weather pattern
 > between different seasons). 

This is, to my mind, pretty much implied by "semi-arid".  Only the
most arid zones lack seosanl rainfall.  Even most of the North American
deserts have a distinct rainy season. [I restrict the term "monsoon"
to climates with seasonal *heavy* rains].

 >There's certainly lots of evidence for
 > arid times/areas, but there's also strong evidence for wetter
 > times/areas. 

Even in a rather arid climate, the land along major river courses
is usually much moister.


The picture that seems to be best is of a mostly semi-arid climate with
gallery forests along major watercourses and fern savannas elsewhere
(at least in the basinal areas), transitioning locally to either truly
arid climates (the sand dunes) and to subhumid monsoon climates with
open woodlands and occasional swamps.



This is very different than the coniferous forests depicted in the
show I saw part of.

swf@elsegundoca.attgis.com              sarima@netcom.com

The peace of God be with you.