Biology Reference
In-Depth Information
The Appalachian Mountains
North America is bordered on the east by the Appalachian Mountains,
including the adjacent slopes or piedmont, and by the Atlantic and Gulf
coastal plains. The mountains extend 3000 km from Alabama to Newfound-
land and are part of an even larger system that continues into England,
Scotland, Scandinavia, and in scattered regions north of the Alps as the
Caledonian and Hercynian mountains. They are Paleozoic in age and have
undergone about 300 million years of erosion that has resulted in relatively
low elevations (Mt. Mitchell in North Carolina is the highest at 2037 m),
and characteristic rounded domelike structures such as Clingman's Dome
(2025 m) in the Blue Ridge Mountains of Tennessee. These ranges are
mostly covered by the eastern deciduous forest, which constitutes about
11 percent of the plant cover of North American north of Mexico (fi g. 2.4).
With at least sixty-seven genera of trees and shrubs that form its canopy and
subcanopy, the forest represents the richest of the plant formations. The
most widespread association within the deciduous forest is
Quercus
-
Carya
(oak-hickory) on drier and sandy sites, and the richest association is
Fagus
-
Acer
(beech-maple) in more mesic localities. These associations reappear
along the east-facing slopes of the Sierra Madre Oriental of Mexico, with
the distribution interrupted by the Chihuahuan Desert of south Texas and
northern Mexico, and as we shall see in chapter 9, they also occur in the
forests of central China. Study of such disjunct occurrences is part of the
fi eld of biogeography, and their explanation depends on information from
geology and climatic history, fossil records, a knowledge of the ecological
requirements of the extant organisms, the distribution potential of their
propagules, and a phylogenetically sound taxonomy (I, chap. 9).
Much of the coastal plain is covered by pine forest of
Pinus taeda
(loblolly
pine),
P. echinata
(short-leaf pine), and
P. palustris
(long-leaf pine). There are
grasslands in central Florida with scattered
Sabal
(palmetto) forming palm
savannas, and mangroves (
Rhizophora mangle
) fringe the coast (see fi g. 2.24
below). Swamp and fl oodplain forests of black gum (
Nyssa
) and bald cy-
press (
Taxodium distichum
) grow inland along the southern Gulf Coast.
One of the most fascinating environments of eastern North America is
the quiet, serene, almost mysterious cypress swamp, with its festooning
Spanish moss (
Tillandsia usneoides
), silently gliding alligators (
Alligator mis-
sissippiensis
), and cottonmouth water moccasins (
Agkistrodon piscivorus
).
This has made it a frequent locale for fi lms such as
Southern Comfort
,
which recounts the fi ctitious, abusive, and ill-advised confrontation of
nine National Guardsmen with the local inhabitants. My Cajun relatives in
