|
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.〔(【引用サイトリンク】url=http://www.miamidade.gov/derm/hardwood_hammock.asp )〕 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. ==Tropical hardwood hammocks== (詳細は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.〔(【引用サイトリンク】url=http://crocdoc.ifas.ufl.edu/publications/msrpmap/tropicalhardwoodhammock/ )〕 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.〔 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'').〔(【引用サイトリンク】url=http://www.nps.gov/ever/naturescience/hardwoodhammock.htm )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hammock (ecology)」の詳細全文を読む スポンサード リンク
|