AMERICA'S SUBTROPICAL WONDERLAND

Tree-island Glades

Beyond the pinelands the road, having descended some 2 feet from the park entrance, brings you into the true everglades—the river of grass, or, as the Seminoles call it, Pa-Hay-Okee (grassy waters). To the eye, the glades look like a very flat, grassy prairie broken by scattered clumps of trees. During the dry season (winter) it is in fact a prairie—and sometimes burns fiercely. The dominant everglades plant is sawgrass (actually not a grass but a sedge). The tree islands develop in both high and low spots of the glades terrain. In this unbelievably flat country, small differences in elevation—measured in inches rather than feet—cause major differences in the plantlife: tropical hardwoods on the "mesas," and swamp trees in the potholes.

A spot in the glades where the limestone base is elevated just 2 feet will be occupied by a small forest of tropical hardwoods and palms—a "hammock" much like those of the pinelands. A low spot—just a few inches below the general level of the limestone base—will remain wet even in the relatively rainless winter when the sawgrass becomes tinder dry. This sloughlike depression will support a stand of baldcypress, called a "cypress head." Other tree islands, called bayheads and willow heads, develop in many places where soil and peat accumulate.

Step from the sawgrass glades into one of these hammocks or heads; you will find yourself in another world. You cannot know the park until you have investigated these plant-and-animal communities so distinct from the surrounding marsh yet so much a part of it. As you drive through the park, look for the trails provided to give you easy access into the interior of the tree islands.

TREE-ISLAND GLADES. (elevation: 1 to 3 feet above sea level) (click on image for an enlargement in a new window)

Also characteristic of the glades are the sloughs—channels where the glades water, generally a thin, seemingly motionless sheet, is deeper and has a noticeable current. The sloughs support a rich plantlife and attract a variety of animals, particularly during the dry season when the water level drops below the shallow glades bottom. Animals that live in the glades when they are under water must migrate or estivate (see glossary) if they are to survive the rainless months. Many migrate to the sloughs, the best known of which is Taylor Slough, where the elevated Anhinga Trail enables you to walk over the water and observe the wildlife.

Fire is an important factor in the ecology of the tree-island glades, just as it is in the pineland. Here, too, artificial barriers such as canals and roads have hindered the spread of natural fires. There is some evidence that tree islands were scattered more thinly over the sawgrass prairie a half-century ago, when a single fire might wipe out scores of them and destroy much of the bed of peat that provided a foothold for them. A bird's-eye view of the glades region today shows many tree islands that have been established in recent decades. But park rangers are now utilizing controlled fires in the glades as well as in the pineland. This tends to prevent new tree islands from taking hold, and thus helps maintain the natural everglades landscape.

Driving over the glades toward Florida Bay, you come to a sign reading "Rock Reef Pass—Elevation 3 Feet." The road then traverses the so-called dwarf cypress forest. The forest is an open area of scattered, stunted pondcypresses—a variety of baldcypress—growing where marl (which, unlike peat, does not burn) has accumulated in small potholes dissolved in the limestone. These marl potholes provide a foothold for the dwarf cypresses in an area that is spotted with cypress heads containing much larger trees. Many of the pondcypresses are more than 100 years old, while tall baldcypresses in the heads may be less than 50 years old. These anomalies can be attributed to varying soil depths and water levels and to the effects of fire.

Before you reach the limit of the fresh-water marsh you will come to a side road leading to Mahogany Hammock. (A good foot trail makes it easy to explore this hardwood jungle island.) Just beyond, you will notice the first red mangroves. Small and scattered in this zone, they are a signal that you are approaching a strikingly different plant-and-animal community, the mangrove swamp.