Cove Hardwood Forest: Remnant of the Arcto-Tertiary Forest
Sixty million years ago, dinosaurs had recently
disappeared from the earth and mammals were just starting to take their
place. The vast Arcto-Tertiary forest coated the northern latitudes of
North America, Europe, and Asia with broadleaf deciduous trees much
like the ones you see around you today. Beech, chestnut, elm, alder,
birch, hornbeam, aspen, walnut, hazel, sweetgum, sequoia, and ginkgo
shared the canopy.
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Just like in
our current Appalachian forests, the trees of the Arcto-Tertiary forest
turned brilliant shades of yellow, orange, and red before dropping
their leaves in the winter. And in early spring before the leaves
returned, herbaceous perennials on the forest floor burst into bloom,
only to fade away as the trees regained their leaves.
This rich forest depended on a warm, humid climate and
before long its range began to contract. Two or three million years
ago, the glaciers of the first ice age drove the plants of the
Arcto-Tertiary forest south. The glaciers melted then re-formed time
after time. In Europe, the Arcto-Tertiary forest was battered up
against the east-to-west aligned Alps until most plants perished. Much
of North America and Asia had turned into grasslands as the climate
dried, so on these continents the forest became restricted to a couple
of mountain ranges --- those in eastern North America and those in
In these two refuges, the forest survived by
migrating north and south as the climate warmed and cooled. The
mountains provided protected nooks and crannies --- high elevation
ridges where cool-loving species could grow during warm spells and
sheltered valleys where warm-loving species could grow during ice ages.
Here in North America, the Arcto-Tertiary forest eventually became
limited to a little tract of mountain land spanning eastern Tennessee,
eastern Kentucky, southwestern Virginia, and southern West Virginia.
After the glaciers finally receded, plants
from the Appalachian refuge began to reforest the surrounding areas.
Birches, beeches, and maples spread north into New England. Oaks and
chestnuts were carried south and east by squirrels and Blue Jays while
other oaks and elms ventured west into the drier prairies. But nearly
every species retained a foothold here, making up the diverse cove
forest types that are named by their dominant trees --- oak-hickory and
beech-maple, for example --- the cove hardwood forest is distinguished
by its lack of dominant trees. Instead, dozens of species can be found
growing side by side, many of them closely related to the trees that
grew here 65 million years ago. Some of these trees, such as the
Tulip-tree (also known as Yellow Poplar or Tulip Poplar), have
relatives in only one other part of the world --- the mountains of
eastern China. When I walk the northern leg of the Loop Trail, I
inevitably get lost in my imagination, journeying over continents and
through millions of years back to the Arcto-Tertiary forest that once
dominated the northern hemisphere.