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G036 Taxodium ascendens / Ilex spp. Basin Swamp Group

Type Concept Sentence: This group consists of forested depression wetlands dominated by Taxodium ascendens, with a characteristic and unique dome-shaped appearance which occur within the flatwoods landscapes of the Southeastern Coastal Plain.

Common (Translated Scientific) Name: Pond-cypress / Holly species Basin Swamp Group

Colloquial Name: Pond-cypress Basin Swamp

Hierarchy Level:  Group

Type Concept: This group consists of forested depression wetlands, typically dominated by Taxodium ascendens, with a characteristic and unique dome-shaped appearance in which trees in the center are generally taller than those around the sides. Examples are known from the Coastal Plain of the Carolinas, Georgia, and Florida extending into southern Alabama, Mississippi and Louisiana. Examples occupy poorly drained, isolated depressions which are usually within a pine flatwoods landscape. The oldest and largest individual trees typically occupy the center of these domed wetlands, with smaller and younger individuals around the margins. Many Carolina bays have uniformly flat basins such that canopy trees do not have a domed aspect. Some examples are essentially permanently flooded, while others support water levels that vary substantially from year to year and over longer climatic cycles. Vegetation includes a series of primarily herbaceous and woodland associations. The wettest sites have open water and floating-leaved aquatic vegetation, or marsh vegetation of tall graminoids (primarily sedges). Drier sites often have an open canopy of Taxodium ascendens, with evergreen shrubs and often a dense, often fairly species-rich herbaceous layer beneath.

Diagnostic Characteristics: Wetland forest or woodland dominated by Taxodium ascendens. The vegetation of this group occurs in the warm-temperate climate region, and in the subtropical region of south Florida.

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: Publications since Kartesz (1999) show that Taxodium ascendens used as a nominal species is probably not actually a distinct species. Flora of North America (FNA Editorial Committee 1993) and other more recent publications (Lickey and Walker 2002, Denny and Arnold 2007) consider it to be a variety, the correct name being Taxodium distichum var. imbricarium (Nuttall) Croom. Some intermediate individuals are found in cypress "stringers" and along small blackwater streams. It is not clear if cypress "stringers" should be included here; these are more-or-less linear features that are parts of disconnected drainageways that arise in a pine flatwoods landscape (e.g., CEGL007419). The vegetation of the "stringers" is somewhat analogous to that of the edges of the true "dome swamps." This group includes the subtropical Taxodium ascendens ponds or savannas of the Big Cypress region of southwest Florida; they are included in ~Taxodium ascendens / Annona glabra / Rhynchospora spp. Subtropical Swamp Forest Alliance (A4085)$$.

Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: This is a wetland forest or woodland dominated by the deciduous conifer Taxodium ascendens. In the wettest (semipermanently flooded) sites, there is open water and floating-leaved aquatic vegetation under the canopy of Taxodium ascendens. In the sites which are flooded seasonally or for shorter durations, there is usually an evergreen shrub layer of Ilex or members of the heath plant family (Ericaceae), or they are dominated by graminoids and forbs with shrubs confined to the periphery. Carolina bays, if intact, also can have an elevated sand rim on the southeastern side of the basin, which supports a xerophytic flora quite unrelated to the moisture-dependent species within the bay.

Floristics: Taxodium ascendens is the characteristic tree dominant. Other woody species may include Nyssa biflora, Pinus elliottii, Hypericum chapmanii, Hypericum myrtifolium, Ilex myrtifolia, Ilex coriacea, Ilex cassine, Ilex amelanchier, Eubotrys racemosa (= Leucothoe racemosa), Morella cerifera, Cephalanthus occidentalis, Liquidambar styraciflua, Clethra alnifolia, Lyonia lucida, and Styrax americanus (Drew et al. 1998). Showy, characteristic herbaceous plants in the Carolinas include species of Symphyotrichum, Xyris, Ludwigia, and Solidago (Bennett and Nelson 1991), Rhexia aristosa, Boltonia asteroides, Lobelia boykinii, Polygala cymosa, Rhynchospora careyana, Rhynchospora filifolia, Agalinis linifolia, Coelorachis rugosa, Dichanthelium wrightianum, Lycopus amplectens, Pluchea rosea, and Scleria reticularis; and in Florida include Lobelia floridana, Polygala cymosa, Coreopsis nudata, Lycopus rubellus (= Lycopus angustifolius), Amphicarpum muehlenbergianum, Carex striata, Carex verrucosa, and Carex turgescens, plus many of those listed for the Carolinas. This same suite of species extends westward on the Gulf Coastal Plain, but with allowances for individual species distributions. The wettest sites have open water and floating-leaved aquatic vegetation, or marsh vegetation of tall graminoids.

Dynamics:  Variation in hydroperiod is the most important dynamic, causing rapid major changes in the herbaceous vegetation. Unlike the steeper-sided solution depressions, where many different hydroperiods are present within a short distance and vegetation zones simply shift, the flat-bottomed Carolina bays may experience drastic yearly changes in hydroperiod over their extent. The difference between a dry year when graminoids and forbs dominate, and a wet year when emergent sedges, such as Rhynchospora careyana dominate, often with floating Utricularia radiata, is striking and demands multiple years of inventory to capture a site''s diversity. Many (probably most) plants persist in seedbanks for periods of years when conditions are not suitable. Fire is also an important process, spreading into the bays from adjacent uplands when conditions are dry, and burning the vegetation along the shallow edges or even burning the vegetation completely throughout the depression. Fire prevents invasion by less water-tolerant trees during dry periods, and interacts with flooding to affect vegetation composition. Where fire no longer occurs, Pinus taeda often invades the ponds or bays. Fire may also be important in preventing buildup of organic matter on the soil surface.
Environmental Description:  Climate: The climate is humid, warm temperate. Average rainfall is 100-150 cm (40-60 inches). Hurricanes and other extreme rainfall events provide for an unpredictable hydrological regime. Rarely, as much as half of a year''s rainfall can occur in one week. Soil/substrate/hydrology: This group occurs in isolated wetland depressions called Carolina bays in the Atlantic Coastal Plain. On the Gulf Coastal Plain, these depressions are called limesinks, cypress domes, or cypress ponds. Carolina bays are oriented, oval, shallow depressions with nearly flat bottoms, which range from North Carolina through South Carolina, and into adjacent Georgia. Most Carolina bays in the Outer Coastal Plain occur in sandy sediments and are filled with peat, while most Carolina bays in the Inner Coastal Plain occur in loamy sediments and have mineral soils with clay hardpans. These depressions hold water, due to a combination of rainfall and exposure of a high regional water table. Some are essentially permanently flooded. Others contain water well into the growing season in most years, but water levels vary substantially from year to year and over longer climatic cycles. In any event, it is important to note that pond-cypress swamps are primarily rainfall-fed and are not flooded from river overflow. Fire is an important natural influence during dry periods. Fires may burn out accumulated peat, changing the character of a depression.
Geographic Range: This group is found on the Coastal Plain, from southeastern North Carolina, through South Carolina, and into Georgia, south Florida, and extending into Alabama, Mississippi and eastern Louisiana. Occurrences are numerous and extensive in South Carolina.

Nations: US

States/Provinces:  AL, AR, FL, GA, LA, MS, NC, SC, TX, VA


Confidence Level: Moderate

Confidence Level Comments: No Data Available
Grank: GNR

Greasons: No Data Available
Type Name Database Code Classification Code
Class 1 Forest & Woodland Class C01 1
Subclass 1.B Temperate & Boreal Forest & Woodland Subclass S15 1.B
Formation 1.B.3 Temperate Flooded & Swamp Forest Formation F026 1.B.3
Division 1.B.3.Nb Southeastern North American Flooded & Swamp Forest Division D062 1.B.3.Nb
Macrogroup 1.B.3.Nb.1 Pond-cypress - Slash Pine Swamp Macrogroup M161 1.B.3.Nb.1
Group 1.B.3.Nb.1.a Pond-cypress / Holly species Basin Swamp Group G036 1.B.3.Nb.1.a
Alliance A0652 Bald-cypress - Pond-cypress / Maidencane Lakeshore Swamp Forest Alliance A0652 1.B.3.Nb.1.a
Alliance A3340 Pond-cypress / Swamp Titi Swamp Forest Alliance A3340 1.B.3.Nb.1.a
Alliance A3341 Pond-cypress / Walter''s Sedge Swamp Forest Alliance A3341 1.B.3.Nb.1.a
Alliance A3342 Pond-cypress / Broad-fruit Horned Beaksedge - Redtop Panicgrass Swamp Forest Alliance A3342 1.B.3.Nb.1.a
Alliance A4085 Pond-cypress / Pond-apple/ Beaksedge species Subtropical Swamp Forest Alliance A4085 1.B.3.Nb.1.a
Concept Lineage: No Data Available

Predecessors: No Data Available

Obsolete Names: No Data Available

Obsolete Parents: No Data Available
Synonomy: > Cypress Savanna (Edwards et al. 2013)
= Cypress domes, heads, and islands (Christensen 2000)
= Cypress pond and strand (Ewel 1990b)
> Cypress-Gum Ponds (Edwards et al. 2013)
> Depression Meadows (Bennett and Nelson 1991)
> Non-Alluvial Swamp (Bennett and Nelson 1991)
> Pond Cypress Domes (Kurz and Wagner 1953)
> Pond Cypress Pond (Bennett and Nelson 1991)
> Pond Cypress Savanna (Bennett and Nelson 1991)
= Pondcypress: 100 (Eyre 1980)
Concept Author(s): H. Kurz and K.A. Wagner (1953)

Author of Description: C.W. Nordman

Acknowledgements: B. Sorrie, K. Kirkman

Version Date: 10-07-15
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