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M161 Taxodium ascendens - Pinus elliottii Swamp Macrogroup

The U.S. National
Vegetation Classification
Type Concept Sentence: This is a Southeastern Coastal Plain depression wetland forest or open woodland dominated by the deciduous conifer Taxodium ascendens, with shrubs or graminoid understory.
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Common (Translated Scientific) Name: Pond-cypress - Slash Pine Swamp Macrogroup
Colloquial Name: Pond-cypress Basin Swamp
Hierarchy Level: Macrogroup
Type Concept: This macrogroup 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 Southeastern Coastal Plain of the Carolinas, Georgia, and Florida extending into southern Alabama, Mississippi and southeastern Louisiana. Examples occupy poorly drained, isolated depressions. Remaining examples are usually within a pineland landscape, but some occur in agricultural landscapes. 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. The wettest sites have open water and floating-leaved aquatic vegetation, or marsh vegetation of tall graminoids. 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 in depressions which are dominated by Taxodium ascendens. The vegetation of this macrogroup occurs in the warm-temperate climate region, and in the subtropical region of south Florida. Some examples on lakeshores and edges of large ponds have a canopy of Taxodium distichum. These are mostly at the very northern edge of the range in North Carolina and Virginia. These wetlands are not associated with rivers or creeks. Stringers and other examples which are not isolated have only very slowly flowing water.
Rationale for Nominal Species or Physiognomic Features: Taxodium ascendens and Pinus elliottii var. elliottii are conifers which are characteristic canopy trees in these wetlands. Taxodium ascendens is usually the dominant tree, and has much higher constancy than Pinus elliottii var. elliottii.
Classification Comments: Flora of North America (FNA Editorial Committee 1993) and other more recent publications (Lickey and Walker 2002, Denny and Arnold 2007) consider Taxodium ascendens to be a variety of Taxodium distichum, the correct name then being Taxodium distichum var. imbricarium (Nuttall) Croom. Some intermediate individuals are found in cypress "stringers" and along small blackwater streams. Cypress "stringers" are more-or-less linear features that are parts of disconnected drainageways that can occur in the swales of ancient coastal topographies in a pine flatwoods landscape (e.g., CEGL007419). The vegetation of the cypress "stringers" is similar to the "dome swamps."
Similar NVC Types:
M310 Southeastern North American Ruderal Flooded & Swamp Forest, note:
M067 Atlantic & Gulf Coastal Plain Wet Prairie & Marsh, note: "includes herbaceous graminoid vegetation in coastal plain depressions, which lack or have very sparse Taxodium ascendens."
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 open 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 wetland graminoids and forbs with shrubs scattered or confined to the periphery.
Floristics: Taxodium ascendens is the characteristic and dominant tree. Other woody species may include Cephalanthus occidentalis, Clethra alnifolia, Hypericum chapmanii, Hypericum myrtifolium, Ilex amelanchier, Ilex cassine, Ilex coriacea, Ilex myrtifolia, Eubotrys racemosa (= Leucothoe racemosa), Liquidambar styraciflua, Lyonia lucida, Morella cerifera, Nyssa biflora, Pinus elliottii var. elliottii, and Styrax americanus (Drew et al. 1998). Showy, characteristic herbaceous plants in the Carolinas include species of Ludwigia, Solidago, Symphyotrichum, and Xyris (Bennett and Nelson 1991), as well as Agalinis linifolia, Boltonia asteroides, Coelorachis rugosa, Dichanthelium wrightianum, Lobelia boykinii, Lycopus amplectens, Pluchea rosea, Polygala cymosa, Rhexia aristosa, Rhynchospora careyana, Rhynchospora filifolia, and Scleria reticularis; and in Florida include Amphicarpum muehlenbergianum, Carex striata, Carex turgescens, Carex verrucosa, Coreopsis nudata, Lobelia floridana, Lycopus rubellus (= Lycopus angustifolius), and Polygala cymosa, plus many of those listed for the Carolinas. Many of these species extend westward on the Gulf Coastal Plain to southern Alabama, Mississippi, and southeastern Louisiana. Understory trees and shrubs in southern Florida include Annona glabra, Chrysobalanus icaco, and Ficus aurea. 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 (Kurz and Wagner 1953, Ewel and Mitsch 1978), 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 vegetational 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 macrogroup 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 macrogroup is found on the Southeastern Coastal Plain, from southeastern Virginia, through eastern North and South Carolina, and into Georgia, south Florida, southern Alabama, Mississippi and southeastern Louisiana. Occurrences are numerous and extensive in South Carolina.
Nations: US
States/Provinces: AL, FL, GA, LA, MS, NC, SC, VA
US Forest Service Ecoregions (2007)
Domain Name:
Division Name:
Province Name: Outer Coastal Plain Mixed Forest Province
Province Code: 232    Occurrence Status: Confident or certain
Section Name: Southern Atlantic Coastal Plains and Flatwoods Section
Section Code: 232J     Occurrence Status: Confident or certain
Omernik Ecoregions:
Plot Analysis Summary:
Confidence Level: High
Confidence Level Comments:
Grank: GNR
Name:Database Code:Classification Code:
Class 1 Forest & Woodland C01 1
Subclass 1.B Temperate & Boreal Forest & Woodland S15 1.B
Formation 1.B.3 Temperate Flooded & Swamp Forest F026 1.B.3
Division 1.B.3.Nb Southeastern North American Flooded & Swamp Forest D062 1.B.3.Nb
Macrogroup M161 Pond-cypress Basin Swamp M161 1.B.3.Nb.1
Group G036 Pond-cypress Basin Swamp G036 1.B.3.Nb.1.a
Concept Lineage:
Obsolete Names:
Obsolete Parents:
Synonomy: > Cypress Savanna (Edwards et al. 2013)
= Cypress Savanna (Schafale and Weakley 1990)
= Cypress domes, heads, and islands (Christensen 2000)
= Cypress pond and strand (Ewel 1990b)
> Cypress-Gum Ponds (Edwards et al. 2013)
> 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 and R.K. Peet
Version Date: 07Oct2015
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