Forest Types and Life Zones (continued)

EASTERN FOREST TYPES

In the East, and particularly in the Southeast, the life zones are not as readily traceable as those in the West. This is due in part to the fact that in past geologic periods successive great ice sheets from the north advanced as far south as New Jersey and Pennsylvania and pushed some of the northern species southward. In the Southeast, the Gulf Stream and proximity to the Tropic Life Zone are responsible for then subtropical type of vegetation in southern Florida. Furthermore, the eastern forests are characterized by a much greater variety of broadleaf species than are those of the West. For these reasons the eastern forest types are more conveniently tied to eastern physiographic regions than to the life zones used for the western forest types.

Subtropical Forest Type.—Everglades National Park, located in southern Florida, within the Coastal Plain, is remarkable for its subtropical bird life and forest types. The swamps bordering the coastline and inlets support a tree growth made up principally of three species of mangrove. Inland are vast areas of sawgrass dotted with hammocks, which are low, rounded knolls supporting a growth of broadleaf trees and shrubs. Among these are gumbo-limbo, live oak, strangler fig, West Indies mahogany, and cabbage palmetto. Slash pine grows in pure stands on the drier sites of the park, and pond-cypress occurs in strands of stunted trees on low areas. The Florida royalpalm is indigenous to Paradise Key within the park. Numerous other subtropical species of trees of botanical interest, because of their rarity in this country, are also native to the park area.

The Appalachian forests embrace the areas included in Great Smoky Mountains National Park, Blue Ridge Parkway, and Shenandoah National Park. Great Smoky Mountains National Park is the meeting ground of the northern and southern hardwood forest species. Consequently, it has a larger number of known tree species, mostly broadleaf, represented in its forests than in any other area of the National Park System, and possibly more than any other natural area of the continental United States. A total of 131 native tree species are known to occur in this area. A number of these, such as eastern hemlock, silver-bell, red spruce, yellow buckeye, and mountain-ash, grow to record size for those species, while still others become giants. The stands of red spruce and Fraser fir crowning the highest peaks and ridges are an interesting coniferous type which represents a southern extension of the Canadian Life Zone.

The large variety of broadleaf species in the forests of Great Smoky Mountains National Park, Blue Ridge Parkway, and Shenandoah National Park, numbers of them with conspicuous blossoms, together with the undergrowth of azalea, rhododendron, mountain laurel, and other flowering plants, makes these areas a great attraction in the spring when the blossoms and new foliage put in their appearance and in the autumn when the leaves are brilliantly colored. A trip over the scenic highways of these areas during the height of the spring wild flower exhibit, or during the display of autumn colors, is an experience never to be forgotten.

Chestnut, formerly one of the principal broadleaf components of these eastern hardwood forests, is now represented only by the grey skeletons of the dead trees and by sprouts from the roots and stumps. The old trees have been killed by the chestnut blight, caused by an exotic fungus, native to Asia, which was first observed in this country in 1904. The blight kills the chestnut sprouts about the time they reach an age when they begin to bear fruit. Many of these large, dead trees are hollow and furnish homes for numerous birds and mammals.

The most northerly forests in the eastern national parks are those in Acadia National Park, on the southeast coast of Maine, and in Isle Royale National Park, in Lake Superior. Both of these areas lie within the belt in which the upper Transition Life Zone types merge with those of the lower Canadian Life Zone. In each of these parks there are mixed conifer and hardwood types.