The horizontal distance represented on this diagram, from the Pineland to Florida Bay, is 15 miles. With a greatly exaggerated vertical scale, the difference between the greatest elevation of the pine ridge and the bottom of the Florida Bay marl bed is only 14 feet.] FLORIDA BAY (SALT WATER) MUD BANK KEY COASTAL PRAIRIE MANGROVE SWAMP (BRACKISH) BUTTONWOOD LEVEE TREE-ISLAND GLADES (FRESH WATER) BAYHEAD CYPRESS HEAD WILLOW HEAD HARDWOOD HAMMOCK PINE AND HAMMOCK RIDGE Underlying the entire park is porous limestone (_see_ glossary), which was deposited ages ago in warm seas that covered the southern part of today’s Florida peninsula. Over this limestone only a thin mantle of marl and peat provides soil for rooting plants. Some of the park’s ecosystems (_see_ glossary) are extremely complex. For example, a single jungle hammock of a dozen acres may contain, along with giant live oaks and other plants from the Temperate Zone, many kinds of tropical hardwood trees; a profusion of vines, mosses, ferns, orchids, and air plants; and a great variety of vertebrate and invertebrate animals, from tree snails to the white-tailed deer. Pine Rockland Entering the park from the northeast, you are on a road traversing the pineland-and-hammock “ridge.” This elevated part of the South Florida limestone bedrock, which at the park entrance is about 6 feet above sea level, is the driest zone in the park. Pine trees, which will grow only on ground that remains above water most of the year, thrive on this rockland. There is another condition essential to the survival of the pine forest in this region—fire. We usually think of fire as the enemy of forest vegetation; but that is not true here. The pines that grow in this part of Florida have a natural resistance to fire. Their thick, corky bark insulates their trunks from the flames. And strangely enough the fire actually seems to help with pine reproduction; it destroys competing vegetation and exposes the mineral soil seedlings need. If there has been a good cone crop, you will find an abundant growth of pine seedlings after a fire in the pinelands. What would happen if the pinelands were protected from fire? Examine a pine forest where there have been no recent fires. You will note that there are many small hardwood (broadleaved) trees growing in the shade of the pines. These hardwoods would eventually shade out the light-demanding pine seedlings, and take over as the old pines died off. But under normal conditions, lightning-caused fires sweep at fairly frequent intervals through the pineland. Since the hardwoods have little resistance to fire, they are pruned back.