South Florida Rocklands

Most of the upland areas of extreme south Florida are associated with outcroppings of limestone.  Pinelands and tropical hardwood hammocks cover virtually all of these outcrops and are the rockland ecosystems introduced here. 

The area covered by rockland ecosystems is relatively small and shrinking because of the pressure of urban development.  Land required by the expanding population of the greater Miami area and the Florida Keys has been obtained largely by clearing pinelands and hammocks. 

• Surface Geology and Location

  South Florida rockland outcrops are primarily marine limestone and occur in three distinct geographical regions: 

  • The Miami rock ridge is located from Miami to the town of Homestead - This is the largest outcrop;
  • the upper and lower Florida Keys; and
  • the southeast corner of Big Cypress Swamp
• Land Use and Conservation

  Many hammocks and pinelands have been cleared for agriculture and urban development, but several are protected on various federal, state, and local government lands.

  Protected Hammocks

  Despite the loss of large important forests in Dade county, more than half of the tropical hardwood hammocks that were there at the beginning of settlement still exist.  Several hammocks are owned by Dade county and most of the remaining undeveloped hammocks have been proposed for purchase by the state's Conservation and Recreation Lands (CARL) program. 

  Most hardwood hammocks on the Florida Keys are privately owned and are not protected against clearing.  Demand for commercial and residential development on the Keys is such that all privately held land is almost certain to be cleared eventually. 

  A few large tracts of hammocks are protected by the federal government: 

  • Biscayne National Park in the upper Keys
  • The National Key Deer Refuge in the lower Keys

  Two major land acquisition programs are underway on Key Largo:

  • The Crocodile Lakes National Wildlife Refuge of the U.S. Fish and Wildlife Service, and
  • The North Key Largo Hammock Preserve of the Florida Department of Natural Resources.

  These will add substantially to the total area of protected rocklands in the Keys.

  Protected Pinelands

  Pineland areas have been much more devastated than have the hardwood hammocks.  Aside from Long Pine Key in Everglades National Park, the only large areas of Pineland are: 

  • Navy Wells Pineland Preserve owned by Dade County
  • Pinelands on the Deering Estate at Cutler owned by Dade County
  • Pinelands around Richmond Air Field owned by several government agencies

  The largest of the remaining pinelands have been proposed for purchase by the CARL program.  However, passive protection is not sufficient to preserve the pineland ecosystem. 

  They must be burned regularly and the small size of the remaining pinelands combined with the presence of residential and commercial development greatly restrict burning  programs.

• Exotic Plants

  Exotic plants present a major threat to hammocks, pinelands and other ecosystems throughout south Florida.  Several trees planted as ornamentals in south Florida invade plant communities and displace native species.  Threatening exotic plants include:

  • Schinus terebinthifolius (Brazilian pepper) - this plant is the worst invader of infrequently burned pinelands.
  • Bischofia javanica
  • Schefflera actinophylla
  • Colubrina asiatica - a woody vine which smothers hammocks in coastal areas
  • Syngonium - a herbaceous vine
  • Sansevieria - a ground-covering herbaceous plant
  • Melaleuca quinquenervia - this tree is a major threat to the south Florida rocklands ecosystems within the boundaries of the Big Cypress Preserve and to other ecosystems throughout south Florida.

  Active management is necessary to control these exotics!!

  For more information about these and other invasive exotic plants in Florida, visit the Florida Exotic Pest Plant Council Web site.

Rockland Ecosystems

• Tropical Hammocks

  Tropical hardwood hammocks occupy elevated, relatively fire-free sites in all three major rockland areas, and are usually small patches of broad-leaved forest surrounded by other vegetation types. 

  Vegetation

  Hammocks are broad-leaved, evergreen forests composed primarily of trees common to the Bahamas and Greater Antilles.  These forests have a great diversity of orchids, bromeliads and ferns (tropical epiphytes - plants that grow on trees).  More than 150 species of trees and shrubs are native to the rockland hammocks of Dade, Monroe and Collier counties.

  The structure and composition of tropical rockland hammocks are variable and are influenced by regional gradients of rainfall, minimum temperature, disturbances (fire and hurricanes), local gradients of saline influence (especially in the Keys), surrounding vegetation types, and the elevation and character of the limestone substrate.

  Mr. Bill Casey, a forest scientist who earned his M.S. at the University of Florida School of Forest Resources and Conservation, developed a useful table of the common trees in Florida hardwood forests.  Some of these species are native to the tropical rockland hammocks.  These species are followed by the symbol TH, indicating that they are found in tropical hammocks. View the table of common trees in Florida hardwood forests.

  As stated above, there are over 150 species of trees and shrubs native to this ecosystem type and it is beyond the scope of this site to introduce them all.  If you would like more information on the vegetation of this ecosystem, consult the book, Ecosystems of Florida edited by R.L. Myers and J.J. Ewel, or a field guide to the vegetation of the region.

  For more information on these and other trees and shrubs, see our Trees of Florida page.

  Threatened or Endangered Plants

  Trees: 

  • brittle thatch palm (Thrinax morrissii)
  • buccaneer palm (Pseudophoenix sargentii)
  • cupania (Cupania glabra)
  • Florida thatch palm (Thrinax parvitolia)
  • Krug's holly (Ilex krugiana)
  • lignum-vitae (Guaiacum sanctum)
  • manchineel (Hippomane mancinella)
  • silver thatch palm (Coccothrinax argentata)
  • tree cactus (Cereus robinii)

  Shrubs: 

  • pride-of-big-pine (Strumpfia martima)

  Herbaceous Plants and Vines: 

  • auricled spleenwort (Asplenium auritum)
  • bird's nest spleenwort (Asplenium serratum)
  • slender spleenwort (Asplenium dentatum)
  • cowhorn orchid (Cyrtopodium punctatum)
  • dollar orchid (Encyclia boothiana)
  • Everglades peperomia (Peperomia floridana)
  • fragrant maidenhair fern (Adiantum melanoleucum)
  • Fuch's bromeliad (Guzmania monostachia)
  • adder's tongue fern (Ophioglossum palmatum)
  • Hattie Bauer halberd fern (Tectaria coriandrifolia)
  • night-scent orchid (Epidendrum nocturnum)
  • narrow strap fern (Campyloneurum angustifolium)
  • powdery catopsis (Catopsis beteroniana)
  • star-scale fern (Pleopeltis revoluta)
  • twisted air plant (Tillandsia flexuosa)
  • worm-vine orchid (Vanilla barbellata)
  • young-palm orchid (Tropidia polystachya)

  Fauna

  Tropical hammocks provide habitat for a variety of wildlife species, many of which are unique to this habitat. 

  Mammals 

  • Everglades mink (Mustela vison)
  • gray squirrel (Sciurus carolinensis)
  • Key deer (Odocoileus virginianus clavium)
  • Key Largo cotton mouse (Peromyscus gossypinus)
  • Key Largo woodrat (Neotoma floridana)
  • marsh rabbit (Sylvilagus palustris)

  Threatened or Endangered Wildlife

  Mammals: 

  • Florida panther (Felix concolor coryi)
  • Key deer (Odocoileus virginianus)
  • Key Largo cotton mouse (Peromyscus gossypinus)
  • Key Largo woodrat (Neotoma floridana)
  • Key Vaca raccoon (Procyn lotor auspiciatus)
  • mangrove fox squirrel (Sciurus niger avicennia)

  Birds:

  • bald eagle (Haleaeetis leucocephalus) (currently off the endangered list)
  • white-crowned pigeon (Columba leucocephala)
  • wood stork (Mycteria americana)
• Pinelands

  Vegetation

  Canopy

  The single canopy species in the rockland pinelands is the south Florida variety of slash pine (Pinus elliottii var. densa), which is closely related to longleaf pine(Pinus palustris) and Caribbean pine (Pinus caribaea). 

  Subcanopy

  Subcanopy development is rare in most rockland pinelands.  Only occasional hardwoods growing on sites protected from fire reach tree size.  In some of the lower Florida Keys there is a well-developed subcanopy of palms.

  Shrubs

  • pond cypress(Taxodium ascedens)
  • pond apple(Annona glabra)
  • buttonbush(Cephalanthus occidentalis)
  • willow(Salix caroliniana)
  • elderberry(Sambucus canadensis)
  • buckthorn(Bumelia reclinata)
  • beauty berry(Callicarpa americana)
  • varnish leaf(Dodonaea viscosa)
  • locust berry(Byrsonima lucida)
  • pineland croton(Croton linearis)
  • staggerbush (Lyonia fruticosa)
  • dwarf live oak (Quercus minima)
  • running oak(Q. pumila)
  • shiny blueberry(Vaccinium myrsinites)

  For more information about these and other trees and shrubs, see our Trees of Florida page.

  Threatened or Endangered Plants

  Trees: 

  • silver thatch palm (Coccothrinax argentata)

  Shrubs: 

  • big pine partridge pea (Cassia keyensis)
  • pride-of-big-pine (Strumpfia maritima)

  Herbaceous Plants and Vines: 

  • night scent orchid (Epidendrum nocturnum)
  • pineland clustervine (Jacquemontia curtissii)
  • tiny milkwort (Polygala smallii)

  Fauna

  The rockland pinelands are home to a variety of wildlife species, including:  

  Mammals 

  • bobcat (Lynx rufus)
  • cotton mouse (Peromyscus gossypinus)
  • marsh rabbit (Sylvilagus palustris)
  • opossum (Didelphis virginiana)
  • raccoon (Procyon lotor)
  • white-tailed deer (Odecoileus virginianus)

  Birds

  • pine warbler (Dendroica pinus)
  • red-shoulder hawk (Buteo lineatus)

  Reptiles

  • pygmy rattlesnake (Sisturus militarius)
  • five-lined skink (Eumeces inexpectatus)

  Threatened or Endangered Wildlife

  Mammals:  

  • Florida panther (Felis concolor coryi)
  • mangrove fox squirrel (Sciurus niger avicennia)

  Birds: 

  • red-cockaded woodpecker (Picoides borealis)

  Reptiles: 

  • eastern indigo snake (Drymarchon coaris couperi)
  • Miami black-headed snake (Tantilla oolitica)

  Fire Ecology

  Fire is required for maintenance of rockland pine forests and partially controls the relative dominance of upland habitats by pinelands or hammocks. 

  Fire in rockland pine forests are surface fires that consume only litter and some understory vegetation. Pine canopies are usually too open to support a crown fire. Fires usually extinguish when they reach hammock margins, but soil fires can occur in hammocks during severe droughts. 

  South Florida slash pine is adapted to fire in the following ways:

  • This tree has long needles that shield vulnerable apical buds.
  • It also has a thick, insulating bark that protects the living inner bark and cambium.
  • Seedlings have thicker stems and are more fire-resistant than typical slash pine seedlings.

  As the time between fires lengthens, the development of larger hardwoods and the accumulation of litter shift the balance in favor of hardwoods.  Within 2 to 3 decades of fire exclusion, rockland pinelands become tropical hammocks with a relict overstory of pines.