, Volume 3, Issue 4-5, pp 213-265

Southeast saline Everglades vegetation, Florida and its management

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Abstract and summary

The Southeast Saline Everglades is a distinct geographical area, lying entirely in Dade County, Florida, bounded on the north and northwest by pineland, on the east and south by the ocean and its mangroves, and on the west by aquatic vegetation on land permanently submerged. This is a low flat wet region, partaking collectively of certain characteristics of river, swamp, fen, marsh, tidal-marsh, lake, and even upland. By referring to this area as “saline” is it not implied that the region is continuously saline or that the marl was formed under saline conditions. The term is used to indicate that the vegetation is in adjustment with sporadic hurricane floods of ocean waters, which not only serve as dissemination agents for certain kinds of plants, but which affect the presence and distribution of other plants according to their tolerance to salinity. In respect to this sporadic saline factor, the region can be segregated from the rest of the Florida Everglades. (As a nomenclatural term, “Saline Everglades” is thus analogous to various “hurricane forests” and “fire types”, named with reference to historic events and not the continuing environment.)

The vegetation of this area is an endless prairie, dotted with dense tree hammocks, developed on a thin layer of Recent freshwater marl, overlying a calcareous oolite, in a tropical climate. The present complex vegetation appears to be a “fossil” phenomenon, developed under past conditions of higher water tables and Indian fires, and now rapidly disappearing. This vegetation has supported large populations of wildlife, especially the larger birds. The bird-supporting plant communities however are to a certain extent no longer self-perpetuating, and the management of these lands will require some unprecedented manipulation of the water, fire and other factors. Construction of highways and railroads and agricultural practices have interfered with surface drainage, and directly changed large areas of the natural vegetation. Agricultural values have been in part nullified by encroaching subsoil salinity. Casuarina equisetifolia, a naturalized tree of increasing economic value, is producing a new self-perpetuating forest.

The Saline Everglades and vicinity can be described in terms of seven belts, each with its own aggregate of past present and future communities, its own contemporary vegetation-change, and its own possibilities of management. Description of many of these communities is in terms of quadrat data and sample plots.

  1. The Miami Pineland, on the Miami oolite of the Atlantic Coastal Ridge and the Everglades Keys, an open frequently burned forest of Pinus caribaea, with dense tropical unburned hammocks.

  2. A narrow transitional belt of non-sawgrass, non-pine, Aristida grassland; sometimes absent.

  3. A major belt of sawgrass prairie with hammocks of Persea (bay tree) on peat; in part used for agriculture, partly abandoned because of encroaching sub-surface salinity; water levels greatly lowered; hammocks being destroyed by fire; open to Casuarina invasion.

  4. A minor belt of sawgrass prairie, dotted with hammocks, and developing to low Rhizophora; sparse vegetation assumedly related to past fires and to periodically high salinities; open to Casuarina invasion.

  5. A minor belt of sawgrass prairie, without tidal-marsh species, development to tall Rhizophora and Avicennia swamp in the intervals between hurricanes; open to Casuarina invasion. Hammocks sometimes present, with tall Avicennia predominant.

  6. A mangrove belt of Rhizophora and Avicennia, with Rhizophora predominant after hurricanes, and with tidal-marsh “emerging” when trees are absent. Casuarina invades the upper margin of this belt.

  7. A Rhizophora mangrove belt, fronting the ocean, composed almost solely of Rhizophora mangle.

These belts apparently represent a normal sequence for tropical vegetation passing from upland through winter-dry swamp, to shallow ocean shores. Lowered water tables appear to be effecting a mass seaward shift of Belts 1 and 2. Rising sea level would effect a landward shift of Belts 4, 5, 6 and 7, with the seaward side of Belt 7 possibly exhibiting a lag due to organic and inorganic deposition related to the mangrove. Belt 3, the major belt of the area, becomes narrower as a result of this encroachment from both sides.