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A1817 Isoetes spp. - Amphianthus pusillus Granitic Outcrop Pool Alliance

Type Concept Sentence: This vegetation is dominated by Isoetes lithophila, Isoetes melanopoda, Isoetes melanospora, Isoetes tegetiformans, and Amphianthus pusillus which occur in seasonally flooded pools of granitic outcrops of the southern United States in Georgia, South Carolina, Alabama, and central Texas.

Common (Translated Scientific) Name: Quillwort species - Poolsprite Granitic Outcrop Pool Alliance

Colloquial Name: Granitic Outcrop Pool

Hierarchy Level:  Alliance

Type Concept: This vegetation is endemic to freshwater rock pools on granitic flatrocks and domes of the southern United States. Examples on granitic outcrops of Georgia, South Carolina, and Alabama are generally dominated by Amphianthus pusillus, Isoetes melanospora, and/or Isoetes tegetiformans, in seasonally flooded pools. Other species which may occur are Callitriche heterophylla, Cyperus granitophilus, Pilularia americana, and Juncus georgianus. In addition, the winter annual Diamorpha smallii may occupy adjacent marginal areas of this community, which are flooded for shorter periods of time. In central Texas, examples occur in freshwater rock pools on granite outcrops of the Llano Uplift. These are characterized by Anagallis minima, Bacopa rotundifolia, Callitriche heterophylla, Crassula aquatica, Elatine brachysperma, Heteranthera limosa, Isoetes lithophila, Isoetes melanopoda, Juncus diffusissimus, Lepuropetalon spathulatum, Mimulus glabratus var. jamesii, Pilularia americana, and Plantago heterophylla.

Diagnostic Characteristics: This is a very distinctive vegetation type which is restricted to seasonally flooded pools on granitic outcrops of Georgia, South Carolina, Alabama, and central Texas.

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: Coffey (1964) cites Isoetes melanopoda as occurring "in crevices and depressions where water collects from the winter rains," with Amphianthus pusillus growing "in abundance around the edges of the Isoetes patches." She does not name or identify either particular zones or specific associations in her work on flat granitic outcrops. Wharton (1978) does not discuss these granite outcrop pools other than citing the work of Baker (1956).

Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: Herbaceous annuals and perennials which tolerate flooding and occur in small pools on granite outcrops. These include emergent and floating-leaved herbaceous plants. Pools may be dominated by Isoetes spp., which are emergent or submerged fern allies, but look like a graminoid plants. Isoetes melanospora and Isoetes tegetiformans use a type of Crassulacean Acid Metabolism (CAM) which allows survival in inundation and in extreme drought (Keeley and Zedler 1998b, Shure 1999).

Floristics: This vegetation in the southern Piedmont is dominated by Amphianthus pusillus, Isoetes melanospora, and/or Isoetes tegetiformans, all of which are endemic to seasonally flooded pools on granitic flatrocks of the southeastern United States. Other species which may occur in the pools or along the edges are Callitriche heterophylla, Cyperus granitophilus, Isoetes melanopoda, Juncus bufonius, Juncus georgianus, Pilularia americana, and Rhynchospora globularis var. saxicola (= Rhynchospora saxicola) (McVaugh 1943, Burbanck and Platt 1964, Edwards et al. 2003, McMillan 2007). In addition, Diamorpha smallii may occupy adjacent marginal areas of this community, which are flooded for shorter periods of time (Hilton and Boyd 1996). In central Texas, examples occur in freshwater rock pools on granite outcrops of the Llano Uplift. These are characterized by Anagallis minima, Bacopa rotundifolia, Callitriche heterophylla, Crassula aquatica, Elatine brachysperma, Heteranthera limosa, Isoetes lithophila, Isoetes melanopoda, Juncus diffusissimus, Lepuropetalon spathulatum, Mimulus glabratus var. jamesii, Pilularia americana, and Plantago heterophylla (Walters and Wyatt 1982, Holmes et al. 2005, cited in Poole et al. 2007, Singhurst et al. 2007).

Dynamics:  No Data Available
Environmental Description:  This vegetation is restricted to seasonally flooded pools on granitic outcrops of the southern United States, in Texas, Alabama, Georgia, and South Carolina. These can occur on granitic domes, or on granite flatrock outcrops. These pools hold water for several weeks in the winter and spring, but dry out in the late spring and become very dry in the summer. Soil depths are 0.1 to 10 cm (Hilton and Boyd 1996). The temperature, dissolved oxygen, dissolved carbon dioxide, and pH of the water in vernal pools can vary significantly over a 24-hour period (Keeley and Zedler 1998b). At the surface of the outcrops, summer temperatures can reach 120°F. This combination of flooding for several weeks, and very hot and dry summer conditions represents an extreme habitat.
Geographic Range: Vegetation of this alliance is found in the southern Piedmont from Alabama to South Carolina and on the Llano Uplift in central Texas.

Nations: US

States/Provinces:  AL, GA, MO, SC, TX


Confidence Level: Low

Confidence Level Comments: No Data Available
Grank: GNR

Greasons: No Data Available
Type Name Database Code Classification Code
Class 2 Shrub & Herb Vegetation Class C02 2
Subclass 2.C Shrub & Herb Wetland Subclass S44 2.C
Formation 2.C.4 Temperate to Polar Freshwater Marsh, Wet Meadow & Shrubland Formation F013 2.C.4
Division 2.C.4.Nd Eastern North American Temperate Freshwater Marsh, Wet Meadow & Shrubland Division D323 2.C.4.Nd
Macrogroup 2.C.4.Nd.2 Broadleaf Cattail - White Snakeroot - Rush species Marsh, Wet Meadow & Shrubland Macrogroup M069 2.C.4.Nd.2
Group 2.C.4.Nd.2.c Quillwort species - American Pillwort - Greater Water-starwort Granite Outcrop Pool Group G803 2.C.4.Nd.2.c
Alliance A1817 Quillwort species - Poolsprite Granitic Outcrop Pool Alliance A1817 2.C.4.Nd.2.c
Association CEGL004342 Poolsprite - Blackspore Quillwort - Merlin''s-grass Granite Pool Vegetation CEGL004342 2.C.4.Nd.2.c
Association CEGL007083 Rock Quillwort - Blackfoot Quillwort - Water Pygmyweed - Matted Water-starwort Granite Pool Vegetation CEGL007083 2.C.4.Nd.2.c
Concept Lineage: The new alliance A1817 is in effect the same as the old A.1817 Amphianthus pusillus - Isoetes spp. Seasonally Flooded Herbaceous Alliance; CEGL004342 is the only member of both; (a one to one relationship).

Predecessors: No Data Available

Obsolete Names: No Data Available

Obsolete Parents: No Data Available
Synonomy: = Continental Climate Granite Outcrop Pools (Keeley and Zedler 1998b)
? Shallow Pool Communities (Quarterman et al. 1993)
= Shallow Pools (Shure 1999)
? Type A (Baker 1956)
= Vernal (Temporary) Pools (Edwards et al. 2013)
> depressions on rock surfaces (McVaugh 1943)
= temporary rock pools (Walters and Wyatt 1982)
Concept Author(s): A.S. Weakley, in Faber-Langendoen et al. (2013)

Author of Description: M. Pyne and C.W. Nordman

Acknowledgements: We have incorporated significant descriptive information previously compiled by A.S. Weakley.

Version Date: 04-21-15
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