Maritime Hammock

Maritime hammocks with a temperate canopy are generally short forests (10 to 12 m) with a monotonous canopy of Quercus virginiana, Sabal palmetto, and Perrea borbonia, plus a structurally diverse understory of woody species including small trees and tall and short shrubs which do not form clear layers. Commonly encountered species include Ardisia escallonioides, Rapanea punctata, Myrcianthes fragrans, Zanthoxylum fagara, Z. clava-herculis, Eugenia axillaris, E. foetida, Psychotria nervosa, and Serenoa repens (Johnson et al. 1992). South of northern Palm Beach County most maritime hammocks have a tropical canopy composed of a greater variety of trees, including the three most common mentioned above plus: Mastichodendron foetidissimum, Guapira discolor, Coccoloba diversifolia, Simarouba glauca, and Metopium toxiferum. Sabal palmetto continues south as an important component of the canopy and subcanopy; the understory shrubs are also the same southward, except for Myrcianthes fragrans which does not continue south of St. Lucie County. As one goes southward in Palm Beach County more tropical species appear, including silver palm (Coccothrinax argentata) and blackbead (Pithecellobium keyense). The barrier islands of southern Palm Beach, Broward, and Miami-Dade counties were developed early in the century and Alexander (1958), in describing a soon to-be-destroyed hammock near Pompano Beach containing 21 species of tropical trees, referred to the hammock community in this region as essentially extinct. The best remaining examples of this community can be found at JD MacArthur Beach State Park, Ocean Hammock Park, and Gumbo Limbo Nature Center in Palm Beach County (P. Davis, Palm Beach County, personal communication 1998), and at the Bartlett Estate (Bonnet House) south of Hugh Taylor Birch State Park in Broward County.

On the Gulf coast of South Florida maritime hammocks with a temperate canopy of live oak and cabbage palm may be found from Sarasota to Collier counties. As on the east coast, maritime hammocks with tropical canopies occur on calcareous substrates. Composition of canopy and understory of temperate hammocks on the Gulf coast is similar to hammocks on the Atlantic coast; composition of tropical maritime hammock canopies is also similar to those on the Atlantic, but somewhat less diverse. Although one species, Piscidia piscipula , is found on the Gulf and not on the Atlantic coast, six tree species found on the Atlantic are not found on Gulf coast: Amyris elemifera, Guapira discolor, Krugiodendron ferreum, Metopium toxiferum, Ocotea coriacea, and Zanthoxylum coriaceum (Wunderlin et al. 1996; Table 1). Two Atlantic species are replaced on the Gulf by related species in the same genus. Pithecellobium unguis-cati replaces P. keyense and Harrisia aboriginum replaces H. simpsonii from Lee County northward (Wunderlin et al. 1996). Another difference, noted by Harper (1927), is that west coast hammocks tend to have more spiny species (Acanthocereus pentagonus, Agave decipiens, Yucca aloifolia, Opuntia stricta) in the understory than do east coast hammocks. The best examples of maritime hammocks are found on the inland side of Cayo Costa and North Captiva Islands just above the mangrove fringe. Other good examples of temperate maritime hammock are found on inner barrier islands that characterize this coast. These develop when an inlet severs the tip of an island from the remainder and subsequent coastwise growth of outer barrier causes it to overlap its former tip, allowing the development of hammock on the now protected inner island. Such hammock development has occurred on Petersen Island and Whiddon Key at Port Charlotte State Recreation Area in Charlotte County and on Cannon and Johnson Islands at the south end of Keewaydin in Collier County. One of the best developed tropical hammocks in the Gulf coast is found on a shell mound on Josselyn Island in Pine Island Sound, Lee County (Johnson and Muller 1992).

Among animals dependent on maritime hammocks, populations of the insular cotton rat (Sigmodon hispidus insulicola), found in tidal marshes and on hammock edges on Captiva, Sanibel, and Pine Islands in Lee County, are apparently secure enough not to require state-listing as are populations of the lower Keys cotton rat (S. h. exputus) which is found in similar coastal habitats (Humphrey 1992). Migrating songbirds that funnel down the Atlantic coast of Florida on their way to South America use the coastal hammock and strand communities for food and shelter. The northern prairie warbler (Dendroica discolor) and indigo bunting (Passerina cyanea) are declining species that use the peninsular migration route (Enge et al. 1997).

Taken from: U.S. Fish and Wildlife Service. 1999. South Florida Multi-Species Recovery Plan. Atlanta, Georgia. Pp. 3:79-80.

Listed Species Occurring in Maritime Hammock Habitat

  • Florida Panther
  • Eastern Indigo Snake
  • Bald Eagle