Hammock is a term used in the southeastern United States for stands of trees, usually hardwood, that form an ecological island in a contrasting ecosystem. Hammocks grow on elevated areas, often just a few inches high, surrounded by wetlands that are too wet to support them. The term hammock is also applied to stands of hardwood trees growing on slopes between wetlands and drier uplands supporting a mixed or coniferous forest. Types of hammocks found in the United States include tropical hardwood hammocks, temperate hardwood hammocks, and maritime or coastal hammocks. Hammocks are also often classified as hydric (wet soil), mesic (moist soil) or xeric (dry soil). The types are not exclusive, but often grade into each other.
Unlike many ecosystems of the coastal plain of the southeastern United States, hammocks are not tolerant of fire. Hammocks tend to occur in locations where fire is not common, or where there is some protection from fire in neighboring ecosystems. Hammocks have begun developing in historic times in areas where fire has been suppressed through human intervention, or where elevations above wetlands have been created by dredging, mining, road and causeway building, and other human activities. On the other hand, many hammocks have been destroyed by development, as they often occur on higher land in desirable locations, such as barrier islands and other waterfront locations.[1]
The etymology of the term "hammock" is obscure. Dictionaries usually give it as an archaic form of "hummock" ("hammock" appeared in print earlier than "hummock"). "Hammock" is first attested in English in the 1550s as a nautical term for a tree-covered island (a mound of trees) seen on the horizon. "Hammock" is used to refer to stands of hardwood trees on the coastal plain from North Carolina to Mississippi.[2][3][4] Types of hammock described in the literature include:
In the United States, tropical hardwood hammocks are found in southern Florida. Sub-types of hammocks in southern Florida include rockland hammocks on the Miami Rock Ridge and in the Big Cypress National Preserve, Keys rockland hammocks in the Florida Keys, coastal berm hammocks in the Florida Keys and along the north shore of Florida Bay, tree island hammocks in the Everglades, shell mound hammocks, coastal rock barren hammocks in the Florida Keys, and sinkhole hammocks on the Miami Rock Ridge.[5]
The trees forming the canopy of the southernmost tropical hardwood hammocks in Florida are almost all West Indian species. The southern live oak (Quercus virginiana) is the only temperate hardwood species to appear regularly in such hammocks. Hammocks along the east coast of Florida as far north as Cape Canaveral, and along the west coast of Florida as far north as the mouth of the Manatee River on Tampa Bay, include West Indian species as canopy trees, but with increasing numbers of temperate species with increasing latitude, so that tropical hardwood hammocks grade into temperate hardwood hammocks.[1]
The tree island hammocks in the Everglades appear as teardrop-shaped islands shaped by the flow of water in the middle of the slough. Many tropical species such as mahogany (Swietenia mahagoni), gumbo limbo (Bursera simaruba), and cocoplum (Chrysobalanus icaco) grow alongside the more familiar temperate species of southern live oak, red maple (Acer rubrum), and hackberry (Celtis laevigata).[6]
Temperate hardwood hammocks are narrow bands of broadleaf forest that occur on the coastal plain of the southeastern United States. In most of the southeast, including the Florida panhandle, the trees in temperate hardwood hammocks are primarily evergreen. Hardwood hammocks in northern Florida peninsula have a mixture of deciduous and evergreen trees, and hardwood hammocks in southern Florida north of the Everglades have a mixture of evergreen and tropical trees.[11][12][13]
Hydric hammocks, also known as low hammocks,wetland hardwood hammocks, or lowland oak hammocks, grow on soils that are poorly drained or that have high water tables, subject to occasional flooding. They are usually found on gentle slopes just above swamps, marshes or wet prairies. Hydric hammocks are found in scattered locations in Florida north of Lake Okeechobee, with concentrations along the upper St. Johns River, the Atlantic coast of northeastern Florida, and particularly along the Big Bend section of the Gulf Coast of Florida, from Aripeka to St. Marks.[14]
Mesic hammocks
Mesic hammocks are hammocks of the southeastern United States coasts (from North Carolina to Texas) and all of peninsular Florida which grow on soils that are rarely flooded. The canopy of mesic hammocks consists primarily of evergreen hardwoods and cabbage palms. The southern live oak is the most common tree in mesic hammocks. Other trees commonly found in mesic hammocks include southern magnolia, pignut hickory, water oak, and laurel oak. Some of those trees are less frequent or absent in southern Florida (from about Lake Okeechobee south), where tropical species, such as gumbo limbo and satinleaf, may be found. Slash pines and loblolly pines are found in many mesic hammocks. The soil in mesic hammocks is well-drained and rarely flooded, but remains moist due to the shade of the canopy, and the heavy leaf litter that usually occurs in them.[15][16][17]
Xeric hammocks
Xeric hammocks, also known as xeric forests or sand hammocks, grow on well-drained sandy soil, such as old sand dunes, where there is some protection from fire. Xeric hammocks are characterized by sand live oak (Quercus geminata) and saw palmetto (Serenoa repens). Xeric hammocks may develop from scrub or sandhill communities. Scrub-derived hammocks typically include myrtle oak (Quercus myrtifolia) and Chapman's oak (Quercus chapmanii), while sandhill-derived hammocks include turkey oak (Quercus laevis) and bluejack oak (Quercus incana). Xeric hammocks require long-term protection from fire to develop, but once established, are somewhat resistant to fire. Sand live oak and myrtle oak reproduce by cloning, and if allowed to become established, may regrow from the roots if the hammock does burns.[18][19][20]
Prairie hammocks
Prairie hammocks are a sub-type of hydric and mesic hammocks composed principally of live oak and cabbage palm trees. They occur in central and southern Florida in prairies and floodplains, on river levees, and on slopes between dry uplands and wetlands.[21]
Oak domes, also called oak hammocks, grow as small patches on shallow depressions or slight hills. They consist of thick stands of evergreen oaks, and are distinct from their surrounding habitats, which are typically woodlands dominated by longleaf pine.[22]
↑ Vince, Susan W.; Humphrey, Stephen R.; Simmons, Robert W. (September 1989). The Ecology of Hrdric Hammocks(PDF). Biological Report. Washington, D.C.: U.S. Department of the Interior Fish and Wildlife Service. p.4. Retrieved December 12, 2018.
↑ "Tropical Hardwood Hammock". Croc Docs - University of Florida Research and Education Center. Retrieved 24 December 2011.
↑ Vince, Susan W.; Humphrey, Stephen R.; Simmons, Robert W. (September 1989). The Ecology of Hrdric Hammocks(PDF). Biological Report. Washington, D.C.: U.S. Department of the Interior Fish and Wildlife Service. pp.1–3. Retrieved December 12, 2018.
↑ "Mesic Temperate Hammock". Croc Docs - University of Florida Research and Education Center. Retrieved 24 December 2011.
↑ "Hardwood Hammock Forest"(PDF). Florida Fish and Wildlife Conservation Commission. Retrieved 2 January 2012.
↑ "Mesic Hammock"(PDF). Florida Natural Areas Inventory. Retrieved 16 June 2018.
↑ "Xeric Hammock"(PDF). Florida Natural Areas Inventory. Retrieved 31 December 2011.
↑ "Xeric Hammock". University of Florida: Ordway-Swisher Biological Station. Archived from the original on 26 April 2012. Retrieved 31 December 2011.
Temperate rainforest are coniferous or broadleaf forests that occur in the temperate zone and receive heavy rain.
A sandhill is a type of ecological community or xeric wildfire-maintained ecosystem. It is not the same as a sand dune. It features very short fire return intervals, one to five years. Without fire, sandhills undergo ecological succession and become more oak dominated.
Laurel forest, also called laurisilva or laurissilva, is a type of subtropical forest found in areas with high humidity and relatively stable, mild temperatures. The forest is characterized by broadleaf tree species with evergreen, glossy and elongated leaves, known as "laurophyll" or "lauroid". Plants from the laurel family (Lauraceae) may or may not be present, depending on the location.
Myakka River State Park is a Florida State Park, that is located nine miles (14 km) east of Interstate 75 in Sarasota County and a portion of southeastern Manatee County on the Atlantic coastal plain. This state park consists of 37,000 acres (150 km2), making it one of the state's largest parks. It is also one of the oldest parks in the state. It was delineated in the 1930s by the Civilian Conservation Corps. A small portion of the park was the gift of the family of Bertha Palmer to the state. The park is named after the Myakka River.
The Atlantic coastal pine barrens is a now rare temperate coniferous forest ecoregion of the Northeast United States distinguished by unique species and topographical features, generally nutrient-poor, often acidic soils and a pine tree distribution once controlled by frequent fires.
The Appalachian mixed mesophytic forests is an ecoregion of the temperate broadleaf and mixed forests biome, as defined by the World Wildlife Fund. It consists of mesophytic plants west of the Appalachian Mountains in the Southeastern United States.
The Atlantic Plain is one of eight distinct physiographic regions of the United States. The Atlantic Plain of the United States includes portions of the coastal states of Delaware, Florida, Georgia, Maryland, Massachusetts, New Jersey, New York, North Carolina, South Carolina, and Virginia.
Florida sand pine scrub is an endangered subtropical forest ecoregion found throughout Florida in the United States. It is found on coastal and inland sand ridges and is characterized by an evergreen xeromorphic plant community dominated by shrubs and dwarf oaks. Because the low-nutrient sandy soils do not retain moisture, the ecosystem is effectively an arid one. Wildfires infrequently occur in the Florida scrub. Most of the annual rainfall falls in summer. It is endangered by residential, commercial and agricultural development, with the largest remaining block in and around the Ocala National Forest. Lake Wales Ridge National Wildlife Refuge also holds a high proportion of remaining scrub habitat, while the Archbold Biological Station near Lake Placid contains about 20 km2 (7.7 sq mi) of scrub habitat and sponsors biological research on it.
The New England-Acadian forests are a temperate broadleaf and mixed forest ecoregion in North America that includes a variety of habitats on the hills, mountains and plateaus of New England and New York State in the Northeastern United States, and Quebec and the Maritime Provinces of Eastern Canada.
Colt Creek State Park is a Florida State Park in Central Florida, 16 miles (26 km) north of Lakeland off of State Road 471. This 5,067 acre park nestled within the Green Swamp Wilderness Area and named after one of the tributaries that flows through the property was opened to the public on January 20, 2007. Composed mainly of pine flatwoods, cypress domes and open pasture land, this piece of pristine wilderness is home to many animal species including the American bald eagle, Southern fox squirrel, gopher tortoise, white-tailed deer, wild turkey and bobcat.
Before drainage, the Everglades, a region of tropical wetlands in southern Florida, were an interwoven mesh of marshes and prairies covering 4,000 square miles (10,000 km2). The Everglades is both a vast watershed that has historically extended from Lake Okeechobee 100 miles (160 km) south to Florida Bay, and many interconnected ecosystems within a geographic boundary. It is such a unique meeting of water, land, and climate that the use of either singular or plural to refer to the Everglades is appropriate. When Marjory Stoneman Douglas wrote her definitive description of the region in 1947, she used the metaphor "River of Grass" to explain the blending of water and plant life.
Tropical hardwood hammocks are closed canopy forests, dominated by a diverse assemblage of evergreen and semi-deciduous tree and shrub species, mostly of West Indian origin. Tropical hardwood hammocks are found in South Florida or the Everglades, with large concentrations on the Miami Rock Ridge, in the Florida Keys, along the northern shores of Florida Bay, and in the Pinecrest region of the Big Cypress Swamp.
The South Florida rocklands ecoregion, in the tropical and subtropical moist broadleaf forests biome, occurs in southern Florida and the Florida Keys in the United States, where they would naturally cover an area of 2,100 km2 (810 sq mi). These forests form on limestone outcrops with very thin soil; the higher elevation separating them from other habitats such as coastal marshes and marl prairies. On mainland Florida, rocklands exist primarily on the Miami Rock Ridge, which extends from the Miami River south to Everglades National Park. South Florida rocklands are further divided into pine rocklands and rockland hammocks.
The Middle Atlantic coastal forests are a temperate coniferous forest mixed with patches of evergreen broadleaved forests along the coast of the southeastern United States.
The Southeastern mixed forests are an ecoregion of the temperate broadleaf and mixed forest biome, in the lower portion of the Eastern United States.
The Southeastern conifer forests are a temperate coniferous forest ecoregion of the southeastern United States. It is the largest conifer forest ecoregion east of the Mississippi River. It is also the southernmost instance of temperate coniferous forest within the Nearctic realm.
The Southern coastal plain oak dome and hammock is a forest type occurring in small patches in Florida, Georgia, Alabama, and Mississippi. These forests consist of thick stands of evergreen oaks on shallow depressions or slight hills. They are distinct from their surrounding habitats, which are often woodlands dominated by longleaf pine.
The southern coastal plain hydric hammock is a wetland hammock community found on the flat lowlands of the southern and outermost parts of the Atlantic Coastal Plain in the states of Georgia, Florida, and Alabama. These forests of evergreen and deciduous hardwood trees occur near the floodplains of spring-fed rivers with relatively constant flows, usually over limestone substrates. They are usually found on gentle slopes just above swamps, marshes or wet prairies. In places, they can form large areas of broad, shallow wetlands.
Gulf Hammock is a wetlands area in the southern end of Levy County, Florida. It extends along the Gulf of Mexico coast from Cedar Key to the Withlacoochee River, and reaches several miles inland. Gulf Hammock includes the largest expanse of hydric hammock in Florida. The area is mostly uninhabited, with the area closest to the Gulf coast in a state park, and the inland areas primarily used for logging and hunting.
The upland hardwood forests of Florida are closed canopy forests dominated by deciduous and evergreen trees, and shrubs.
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