low latitude paleoflora

[longrich@alumni.princeton.edu]

I think this got rejected since my mail program does some fancy-text 
type thing.

On Saturday, July 20, 2002, at 11:29 PM, Tracy L. Ford wrote:

>>>>>>>>>>>>>>>>>>>>.
Cesari, S. N., Remesal, M, and Parica, C., 2001, Ferns; a palaeoclimate
significant component of the Cretaceous flora of Livingston Island,
Antarctica. VII International Symposium on Mesozoic Terrestrial 
Ecosystems,
p. 45-50.

p. 49.

The esistence of these familes in the Cerro Negro flora suggest a 
FROST-FREE
(me again) climate during the Aptian. Also, Cantrill (1998) suggests that
the presence of Lophosoria cupulatus indicates that the MAT was at least
8degreesC in the southern High Latitudes (that's above freezeing right?) 
in
the southern high latitudes. The current knowledge of the unquestionable
presence of Osmundaceae, Cyatheaceae, Lophosoriaceae, Marattiaceae and 
the
possible presence of Schizaeaceae, Lygodiaceae and Polypodiaceae allow 
us to
recognize ferns as a diverse group in the Early Cretaceous plant 
communities
of the South Shetlands Islands. According to the present requirements of
those families, some of which are restricted to montane forests, tropical
and subtropical, the climate was mild enough YEAR around, so that these
ferns could reach an important ecological role in the community, which is
reflected in the fossil record.

Conclusions

Several macro and microfossil ferns taxa were present during the Early
Cretaceous in the Antarctic region. These belong to several families
including the Osmundaceae, Marattiaceae, Cyatheaceae, and Lophosoriaceae
with the probable representation of Schizaeaceae, Lygodiaceae and
Polypodiaceae. Many of the taxa found in the strata belong to ferns, 
which
now live in wet tropical to subtropical forests. Moreover, some of them
could develop arborescent habit, therefore very cold conditions are
UNTENABLE (me again) in the area during the early Aptian.

Hmmm...

Tracy L. Ford
P. O. Box 1171
Poway Ca  92074
<<<<<<<<<<<<<<<<<<<<<<<

	I did a check on these families. Some of them do seem to have a 
mainly tropical distribution. However, a member of the Osmundaceae is 
found up in Hokkaido; Cyatheacea, the treeferns, are found in New 
Zealand, in particular the popular Dickinsonia antarctica is found up to 
subalpine elevations in Australia  where they don't like really hard 
frosts but they are cold tolerant, lethal temperature is something like 
15-18 Fahrenheit (which is below zero C) and they will survive being 
snowed on no problem. Apparently it can be grown outdoors in places like 
Scotland (with some shelter) and does well in Oregon (Google is a 
freakin' great paleontology research tool by the way...). This is the 
fern for you if you want to grow an archaic-looking forest of 50' tall 
tree ferns... but start soon, since they only grow a couple inches a 
year.
	At least one species of Polypodiacea, I can tell you from 
experience is extremely cold tolerant. Polypodium glycyrrhiza, the 
Licorice Fern (the root tastes like licorice), grows all over the place 
on cliffs on Kodiak Island in Alaska where it can get well below zero F 
and they don't seem to mind, in fact they remain bright green 
year-round. They make cute houseplants and do well in rock gardens with 
a good water supply. Come to think of it the sugars in the rhizome might 
be acting as an antifreeze.
	So at least some of these ferns are currently moderately cold 
tolerant, some are quite cold tolerant. The possibility also exists that 
in the past when these families were more diverse, members may have 
existed which were capable of tolerating temperate, subalpine and 
subarctic conditions. Plants are pretty adaptable. There are I think a 
couple species of prickly pear and one pincushion cactus in Alberta for 
example; they survive temperatures down to forty below.