Everglades Ecology: Habitats

by Donald E. Chamberlain

River of Grass Overview
River of Grass Overview

Everglades National Park is noted for its biological diversity. This diversity of animal life is possible because of a number of different microenvironments existing within the park.
The microenvironments are a result of interaction between three factors: “soil type”, water within a region and differences in elevation of different regions. Interactions between the types of bedrock found in a region and the water flowing through it will determine the types of pioneer plants that can grow there. Ultimately, plant life in that region will determine what animals live there.
As a result of interactions between water flow and small differences in elevation, some regions of the Everglades are water-covered for only part of the year, while other regions are covered with water for the entire year. The amount of time a region is covered with water is called its hydroperiod. The interaction between soil conditions and hydroperiod result in a number of unique microenvironments or habitats found in the Everglades. In this article, I will describe some of those habitats.

Mats of Perphyton
Mats of Perphyton

1. Periphyton:

The term periphyton refers to an ecosystem made up of algae, fungi and other microorganisms. It occurs most commonly where the water has minimal salinity. During the wet season, Periphyton appears as a tan-colored mat floating on the surface of the water.
On a recent trip to the Everglades, while taking a tram ride from the Shark River Valley Visitor Center, I was given an opportunity to wade into the water a few feet from the road. While wading I scooped up a handful of periphyton. Below the tan-colored surface layer was an inch-thick layer of bluish green tissue. This blue-green layer consists of photosynthetic algae and blue-green bacteria. These microbes provide food and an oxygen source for other non-photosynthetic microorganisms in the mat. All these microbes provide a food supply for much larger organisms.

Cypress Head Close Up
Cypress Head Close Up

2. Wetland Tree Islands:

In regions where this fresh water is slowly flowing to the southwest, much of the park is covered by saw grass. It is this vast expanse of saw grass that writer Marjory Stoneham Douglas first described as “a river of grass”. In many areas of the park clusters of trees and shrubs referred to as “tree islands” punctuate this huge expanse of grass. The type of “Tree Island” formed is again determined by the elevation of that growth and the hydroperiod typical of that location. Examples include bay heads, willow heads, and.or cypress heads.

a. The Cypress Dome (Cypress Head):

The cypress tree is a deciduous conifer tree that can tolerate standing water. In some areas of the Everglades where there are water filled depressions with 1-2 feet of peat in the bottom, cypress trees often grow clustered together. If the depression is wide enough, taller trees normally form in the center of the grouping; near the edges, the trees grow shorter resulting in a dome-shaped group of trees called a cypress dome or cypress head. These heads may contain both Bald Cypress and pond cypress trees.

Pine Key Overview
Pine Key Overview

3. Hardwood Hammocks:

When the ground surface remains higher that the surrounding water levels for most of the year, the result may be a small mature hardwood forest or hardwood hammock. This type of hammock may contain tropical hardwoods like live oak, mahogany, gumbo-limbo, hackberry or red maple. Since these habitats rarely flood, native peoples used them for locating their homes, planting their gardens, and housing their livestock. Falling leaf litter decomposition may also form a moat here.
Great examples of hardwood hammocks are the Gumbo Limbo Trail near the Royal Palm Visitor Center and the Mahogany Hammock (accessible off the road to Flamingo).

4. Pinelands:

In areas where the limestone bedrock is found near the surface and soil levels are shallow, slash pine trees will grow. The thin soil favors of this habitat favors pine growth over hardwood growth and also produces conditions favorably to many types a palmettos and other tropical plants.
The Pineland habitat is the most diverse habitats in the Everglades. Fire helps to maintain the pinelands habitat. The pine bark is especially resistant to fire; fire would instead destroy small hardwood seedlings growing in the area.
An example of this type of habitat can be observed at Long Pine Key (four miles from the Visitor Center) and the Pinelands trails (seven miles from the Visitor Center) along the road to Flamingo.

Web of Mangrove Shoots
Web of Mangrove Shoots

5. Mangroves:

Nearing the village of Flamingo, the water becomes saltier.In regions of higher salinity, the predominant pioneer plant to be found is the mangrove. The most common type of mangrove in the Everglades is the red mangrove. This plant is typified by its dense, arching, and intertwining roots. These deep-reaching roots produce a coastal barrier capable of remaining in place in the face of tidal forces and strong winds. The arching roots often provide a roosting place for black crowned or green herons as they sit poised above the water looking for a meal of unwary fish.
Mangrove plants have the ability to extract salt from the water bathing its roots; as a result they occupy areas uninhabitable by other plants. The decomposition of the leaves from the mangrove produces tannic acid that turns the water beneath the mangrove plants a deep rusty red color.
One of the best places to observe the mangrove habitat is along the road to Flamingo is at the West Lake turn-off. A hike along the half-mile boardwalk will deminstrate the density of the mangrove root system.

When next visiting the Everglades, in addition to noting the beauty of the birds and exotic flowers of this marshland, take time to study examples of some of the microenvironments within the park. You will develop a deeper appreciation of the complexity and interrelatedness which typify Everglades National Park.