Tree Islands of the Everglades

Chapter 8.
Vegetation Pattern and Process in Tree Islands of the Southern Everglades and Adjacent Areas

Thomas V. Armentano¹, David T. Jones¹, Michael S. Ross² and Brandon W. Gamble¹
email: tom-armentano@nps.gov
¹South Florida Natural Resources Center, Everglades National Park, 40001 State Road 9336, Homestead, Florida 33034, USA;
²Southeast Environmental Research Center, Florida International University, University Park, Miami, Florida 33199, USA.

From Tree Islands of the Everglades edited by Fred H. Sklar (South Florida Water Management District) and Arnold G. van der Valk (Iowa Lakeside Laboratory)

Abstract

The tree islands of the Everglades area of southern Florida, including adjacent interior and coastal areas, are classified based on species composition and environmental factors controlling tree island distribution and structure. Tree islands occur on various substrates within surrounding habitats that may be freshwater or coastal wetlands, or rockland pine forest of the Atlantic Coastal Ridge. Eight tree island groupings within seven subregions are defined by cluster analysis of data from the literature and previously unpublished studies. Additional types are recognized based on distinguishing ecological features. Most of the types are dominated by native, tropical species found in the continental United States only in southern Florida. Hurricanes, drainage, excessive burning, spread of non-native species and logging have differentially affected all types and few undisturbed tree islands exist even within federally preserved lands. Collectively, the types occur along local and regional elevation gradients, with associated vulnerability to flooding and fires. Marked differences exist in the response of tree islands to protracted flooding that are consistent with their location in the landscape. Thus bayhead swamps, which occur as part of freshwater slough tree islands and are comprised mostly of temperate swamp forest species, have been inundated up to 10 months/yr in the past several decades, while tropical hardwood hammocks on the same tree islands were inundated for 0 to 23% of the year. Hammocks within rockland pine forests seldom if ever flood, but they are subject to periodic fires. A total of 164 woody species occur naturally in the area's forested islands, although many are rare or highly restricted in distribution. All 135 tropical species have distribution ranges centered in the West Indies where most occur in calcareous, dry sites, frequently as invaders of disturbed habitats.

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