# VEGETATION

Vegetation: Many of the same genera, previously part of an Arcto-Tertiary Geoflora, are common to all three of the disjunct northern hemisphere expressions of this biome. Included among these genera are oak, maple, beech, chestnut, hickory, elm, basswood or linden and walnut. Different species of these genera occur on each continent.

Structure and Growthforms: Five layers are recognized:

1. a tree stratum, 60 -100 feet high, dominated regionally by various combinations of the genera listed above;
2. a small tree or sapling layer, with not only younger specimens of the tall trees with species limited to this layer such as (in Virginia) Allegheny serviceberry or shadbush, sourwood, dogwood, and redbud;
3. a shrub layer often with members of the heath family such as rhododendron, azaleas, mountain laurel, and huckleberries;
4. an herb layer of perennial forbs that bloom primarily in early spring; and
5. a ground layer of lichens, clubmosses, and true mosses. Lichens and mosses also grow on the trunks of trees.

Lianas such as wild grape, poison ivy, and Virginia creeper climb the trees to flower and fruit high in the forest canopy.

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