The most extensive natural community in the management area is sawgrass marsh. Sawgrass, which reaches heights of 10 feet or more, thrived in the low-nutrient and fluctuating water conditions of the historic Everglades.
The black peat of the Everglades—valued for agriculture, especially sugar cane—formed over thousands of years from decomposing plants and charcoal from frequent natural fires. Today water levels in the marsh are regulated by water control structures as well as by rainfall, and vary from an average of two feet deep at the peak of the wet season in October to below ground level at the end of the dry season in May. Sawgrass is important to ground-nesting birds such as American and least bitterns, which build elevated mound nests out of dead vegetation and use the thick growth of sawgrass for cover.
Fires every one to five years are typical and result from lightning in the late spring when the ground surface is dry, although sawgrass will carry a fire over water. When the peat dries out in extreme droughts, devastating muck fires may consume the soil and lower the ground surface, converting the sawgrass marsh to a slough.
Although tree islands comprise less than two percent of the Everglades, they are an integral part of the ecosystem. These islands vary in size from less than one acre to several hundred acres but they support over eighty percent of plant diversity in the Everglades. They provide critical habitat for deer, Florida panther, bobcat, raccoon, marsh rabbit, river otter, snakes, migratory songbirds, small mammals and butterflies, and provide nesting sites for wading birds, alligators, turtles, and raptors. Dominant tree and shrub species include red maple, dahoon holly, wax myrtle, elderberry and willow.
The wet prairies of the Everglades are treeless plains with a sparse to dense ground cover of grasses and herbs, including maidencane, spikerush and beakrush. Other typical plants include swamp lily, arrowhead, pickerel weed,Ludwigia spp.and bladderwort. Wet prairies occur on low, relatively flat, poorly drained terrain. They are saturated approximately 90 percent of the year and burn every six to ten years. Sloughs within the Everglades are broad shallow channels inundated with flowing water except during extreme droughts. They often correspond with linear depressions in underlying bedrock. Vegetation consists of large emergent herbs and floating aquatic plants such as white water lily, floating hearts and spadderdock. During the rainy season, sloughs and wet prairies are habitat for a wide variety of fish species as well as snails, crayfish and other invertebrates. As water levels decline during the dry season, fish and invertebrates move to deep water sloughs for refuge. This high concentration of prey during the dry season is a critical source of food for the threatened wood stork and other wading birds. Wet prairies and sloughs are threatened by the spread of melaleuca and cattails.
Holey Land has a section of woody hydric hammock on the western side bordering the Miami Canal levee. Although composed primarily of native species, it is not believed to be a historically occurring natural community on this site. This area has developed through plant succession from sawgrass marsh due to a reduced hydroperiod and lack of fire intrusion caused by its proximity to the levee, and may include a portion of a historical tree island. The canopy is dominated by mature red maples, with a sub-canopy of younger red maples and cabbage palms. The shrub layer includes wax myrtle, Carolina willow, and dahoon holly, with the herbaceous layer being sparse and open. This area provides animals with habitat similar to tree islands and is frequented by species such as white-tailed deer, Florida panther, bobcat, raccoon, armadillo, opossum, marsh rabbit, river otter, snakes, migratory songbirds and small mammals.