Generally, in south Florida, hardwood hammocks develop only in areas
protected from fire, flood, and saline waters. The land must be high
enough (1 to 3 feet above surrounding levels) to stand above the water
that covers the glades much of the year. The roots of the trees must be
out of the water and must have adequate aeration. In the park, these
conditions prevail on the limestone “ridge” (elevation of which ranges
from 3 to 7 feet above sea level) and some spots in the glades region.
On the limestone ridge, in areas bypassed by fires for a long period,
hammocks have developed. Pines grow in the surrounding areas, where
repeated fires have held back the hardwoods.
The moats that tend to form around glades hammocks, as acids from
decaying plant materials dissolve the limestone, hold water even during
the dry season; the moats thus act as barriers protecting the hammock
vegetation from glades fires.
When the white man took over southern Florida, these hammocks were
luxuriant jungle islands dominated by towering tropical hardwoods and
palms. Stumps and logs on the floors of some of the remaining hammocks,
attesting to the enormous size of some of the earlier trees, are sad
reminders of the former grandeur of the hammocks. While most of south
Florida’s hammocks have been destroyed, you can still see some fine ones
protected in the park. At Royal Palm Hammock, near park headquarters,
Gumbo Limbo Trail winds through a dim, dense forest with welcome
coolness on a hot day.
Stepping into a jungle hammock from either the sunbathed glades or the
open pine forest is a sudden, dramatic change. The contrast when you
enter Gumbo Limbo Trail immediately after walking the Anhinga Trail is
striking. While the watery world of Anhinga is dominated by a noisy
profusion of wildlife, the environment of Gumbo Limbo will seem to be a
mere tangle of vegetation. But the jungle hammock, too, has its
community of animals—even though you may notice none but mosquitoes.
Many of its denizens are nocturnal in their habits, but if you remain
alert you will observe birds, invertebrates, and perhaps a lizard.
[Illustration: TREE SNAILS
There are 52 color forms of _Liguus fasciatus_ found in south
Florida.]
[Illustration: _Liguus fasciatus pseudopictus_]
[Illustration: _Liguus fasciatus pictus_]
[Illustration: _Liguus fasciatus ornatus_]
The trees that envelop you as you walk on Gumbo Limbo Trail are mostly
tropical species; of the dominant trees, only the live oak (which grows
as far north as Virginia) can be considered non-tropical. Under oaks and
tropical bustics, poisonwood, mastics, and gumbo-limbos grow small trees
such as tetrazygia, rough-leaf velvetseed, and wild coffee, a multitude
of mosses and ferns, and only a few species of shade-tolerant flowering
plants. Orchids and air plants burst like sun stars from limbs, trunks,
and fallen logs. Twining among them all, the woody vines called lianas
enhance the jungle atmosphere. Adding a final touch are the royal palms
that here and there tower over the hardwood canopy—occasionally reaching
125 feet.
[Illustration: TROPICAL HARDWOOD HAMMOCK]
PINELAND
SOUTH FLORIDA SLASH PINE
BUSTIC
GUMBO-LIMBO
SOLUTION HOLE
POND APPLE
AIR PLANTS (ORCHIDS, BROMELIADS)
ROYAL PALM
LIVE OAK
MASTIC
VINES
PINELAND
SAW-PALMETTO
The limestone rock that underlies the entire park is porous and soluble;
consequently the floor of the hammock is pitted with solution holes
dissolved by the acid from decaying vegetation. Soil and peat
accumulating in the water-filled bottom of one of these holes supports a
plant community of its own: perhaps a pond apple, surrounded by ferns
and mosses (including some varieties that seem to be limited to this
pothole environment).
A dead, decaying log on the ground may support another miniature plant
community—a carpet of mosses, ferns, and other small plants that thrive
in such moist situations.
Strangest of the hammock plants is the strangler fig, which first gets a
foothold in the rough bark of a live oak, cabbage palm, or other tree.
It then sends roots down to the ground, entwining about the host tree as
it grows, and eventually killing it. On the Gumbo Limbo Trail you will
see a strangler fig that grew in this manner and was enmeshed by another
strangler fig—which now is threatened by a third fig that already has
gained a foothold in its branches.
Best known of the glades hammocks is Mahogany Hammock. A boardwalk trail
in this lush, junglelike tree island leads past the giant mahogany tree
for which the hammock was named—now, because of Hurricane Donna, a
dismembered giant. This fine tree island was explored only after the
park was established.
An array of large and small vertebrate animals, mostly representative of
the Temperate Zone, populates these tropical hardwood jungles: raccoons
and opossums, many varieties of birds, snakes and lizards, tree frogs,
even bobcats and the rare Florida panther, or cougar. Not surprisingly,
invertebrates—including insects and snails—abound in this luxuriant
plant community. The tropical influence is evident in the presence of
invertebrates such as tree snails of the genus _Liguus_, known outside
of Florida only in Hispaniola and Cuba.