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G584 Schizachyrium scoparium - Clinopodium arkansanum - Bigelowia nuttallii Southeastern Coastal Plain Barrens & Glade Group

Type Concept Sentence: These are distinct types of glade and barrens vegetation found on various specialized substrates (igneous rock, clay, saline soil, limestone, sandstone) in the coastal plains of the southeastern United States from eastern Texas to northern Florida. Their floras are distinctive to each substrate type.


Common (Translated Scientific) Name: Little Bluestem - Limestone Calamint - Nuttall''s Rayless-goldenrod Southeastern Coastal Plain Barrens & Glade Group

Colloquial Name: Southeastern Coastal Plain Barrens & Glade

Hierarchy Level:  Group

Type Concept: This glade and barrens vegetation is found on various specialized substrates (igneous rock, clay, saline soil, limestone, sandstone) in the coastal plains of the southeastern United States from eastern Texas to northern Florida. It is currently documented from seven distinct areas and their particular substrates. They will each be described separately.

On outcrops of marine sediment and glauconitic clays of the Weches Formation in central eastern Texas, a series of small-patch communities occur primarily in San Augustine, Nacogdoches, and Sabine counties, where they are endemic. These outcrops are exposed by natural erosion of hillside slopes. Soils are shallow, rocky and basic, factors which tend to inhibit growth of woody vegetation. Outcrops are seepy and saturated during winter and early spring but become hard and dry in the summer. Enormous seasonal variations in species dominance can occur. Characteristic species include Sedum pulchellum, Clinopodium arkansanum, and Sporobolus vaginiflorus. A scattered shrub layer, including Cercis canadensis, Cornus drummondii, Juniperus virginiana, and Sideroxylon lanuginosum, may be present on some sites. In addition, the narrowly endemic annuals Lesquerella pallida and Leavenworthia aurea var. texana may be present.

Another series of associations is confined to the Catahoula geologic formation of eastern Texas and western Louisiana. These sites include a vegetational mosaic ranging from herbaceous-dominated areas on shallow soil and exposed sandstone to deeper soils with open woodland vegetation. Seasonal droughtiness, shallow soils, aluminum toxicity, and periodic fires are important factors that influence the composition and structure. The woodland component (which is treated in a separate group) exhibits a post oak-dominated overstory grading into longleaf pine-dominated areas.

In Saline and Pulaski counties, Arkansas, there are glade communities restricted to distinctive, massive outcrops of igneous substrate ("nepheline syenite"). Zonal vegetation communities are present around the outcrops. Interior herbaceous-dominated zones can be mesic to wet as springs and small ephemeral streams flow across the rock outcrops and water pools in flat areas. Deeper, more heavily wooded vegetation develops along the flat or slightly sloping outcrop edges. It is possible that examples also occurred in the adjacent Ouachita Mountains of Arkansas, although extant examples are not known. These are also at least conceptually accommodated here, even though this extends the range off of the coastal plains.

Altamaha Grit glade vegetation occurs on outcrops of indurated sandstone in the Tifton Upland of the Georgia Coastal Plain. Scattered trees and shrubs can be rooted in deeper soils or crevices, including Pinus palustris, Quercus marilandica, and Vaccinium arboreum. Typical herbaceous species include Allium cuthbertii, Aristida beyrichiana, Bigelowia nuttallii, Coreopsis major, Croton michauxii, Liatris squarrosa, Manfreda virginica, Penstemon dissectus, Schizachyrium tenerum, Phemeranthus teretifolius, and Tephrosia virginiana. A typical dwarf-shrub is Hypericum lloydii. Rare or highly restricted species typical of this community are Cuscuta harperi, Evolvulus sericeus, and Penstemon dissectus. Occurrences can be as large as 5 acres. This community typically occurs in a matrix of longleaf pine woodlands.

Sandstone glades of Panhandle Florida are dominated by Bigelowia nuttallii. Other characteristic species include Schizachyrium scoparium var. scoparium and Eurybia hemispherica. Outstanding examples are found at TNC Rock Hill Preserve (Washington County, Florida).

Small-patch limestone glade and outcrop communities are endemic to the Panhandle of Florida (primarily Gadsden and Jackson counties) and adjacent Decatur County, Georgia. This vegetation includes a range of open limestone outcrops on hillsides and hill crests where soils are either very shallow or absent. This grades into shaded, mesic lower slopes near the floodplain of the Chipola River, and some mesic herbaceous patches dominated by Aquilegia canadensis are also included here.

In addition, there are distinctive communities that occur in portions of the coastal plain west of the Mississippi River on soils with high saline content, which in the most extreme examples are generally not conducive to woody plant growth. Thus, the vegetation forms a mosaic primarily consisting of open herbaceous or shrubby plant communities. This type is most common, and best documented in Arkansas and western Louisiana, but also occurs in eastern Texas. There are also related examples in the adjacent Ouachita Mountains of Arkansas; these are also accommodated here, even though this extends the range off of the coastal plains.

Diagnostic Characteristics: Examples of this group are distinguished by their physiognomy (as distinct from surrounding forests and woodlands) and their occurrence on edaphically noteworthy substrates in the coastal plains of the southeastern United States. In general, glades and barrens are better known and more extensive in the interior limestone provinces (interior Low Plateaus, Ozarks). They are naturally heterogeneous in their physiognomy, displaying herbaceous patches interspersed with small trees and shrubs. Prairies in the same or related areas will occur on deeper soils and (under proper management) display a more uniform grassy appearance.

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: This group includes a number of distinctive associations found in the coastal plains of the southeastern United States which are unified by their presence on the shallow soil of rock outcrops, primarily of circumneutral or alkaline strata or saline soils. Stands are characteristically herbaceous in composition, but may have scattered (to dense) woody plants, depending on management and time since last disturbance (including fire).

Similar NVC Types: No Data Available
note: No Data Available

Physiognomy and Structure: Stands of this group are heterogeneous assemblages of herbaceous and woody plants, the proportion and distribution depending on disturbance events and management. The soils are thin, rocky, and in some cases, base-rich (circumneutral to alkaline) or saline.

Floristics: On outcrops of marine sediment and glauconitic clays of the Weches Formation in central eastern Texas, characteristic species include Sedum pulchellum, Clinopodium arkansanum, and Sporobolus vaginiflorus. Other species include Allium drummondii, Anemone caroliniana, Arnoglossum plantagineum (= Cacalia plantaginea), Chamaesyce nutans (= Euphorbia nutans), Croton monanthogynus, Galium virgatum, Ipomopsis rubra, Minuartia patula (= Arenaria patula), Opuntia spp., and Valerianella radiata. A scattered shrub layer, including Cercis canadensis, Cornus drummondii, Juniperus virginiana, and Sideroxylon lanuginosum, may be present on some sites.

Undisturbed examples of the "Catahoula Barrens" of eastern Texas and western Louisiana are dominated by Aristida longespica, Bigelowia nuttallii, Croton michauxii (= Crotonopsis linearis), Schizachyrium scoparium, and Sporobolus silveanus (Marietta and Nixon 1984). Woodlands include a Quercus stellata-dominated overstory grading into Pinus palustris-dominated areas.

Some examples of glades and barrens on distinctive massive outcrops of igneous nepheline syenite in Saline and Pulaski counties, Arkansas, will have open stands of Quercus stellata, but trees may be absent. Some typical dominant grasses include Aristida purpurascens, Piptochaetium avenaceum, Schizachyrium scoparium, and Sporobolus clandestinus. Other herbs may include Camassia scilloides, Clinopodium arkansanum, Delphinium carolinianum, Sabatia campestris, and Phemeranthus calycinus (= Talinum calycinum). Lichens are common on the rocky substrate of some examples.

Sandstone glades of Panhandle Florida are dominated by Bigelowia nuttallii. Other characteristic species include Eurybia hemispherica (= Aster paludosus ssp. hemisphericus) and Schizachyrium scoparium var. scoparium.

On the open calcareous glades of the Panhandle of Florida (primarily Gadsden and Jackson counties; also adjacent Decatur County, Georgia), the dominant herbaceous species are Andropogon sp., Dichanthelium sp., Stenaria nigricans var. nigricans (= Hedyotis nigricans var. nigricans), Helianthus radula, Muhlenbergia capillaris (= var. capillaris), Schoenus nigricans, and Setaria sp. Some additional forbs are Aristida spp., Asclepias viridis, Asclepias viridiflora, Callirhoe papaver, Carex cherokeensis, Delphinium carolinianum ssp. carolinianum, Lepuropetalon spathulatum, Liatris squarrosa, Ponthieva racemosa, Rhynchospora spp., Rudbeckia fulgida, , Selaginella ludoviciana, Solidago discoidea, Stachys crenata, and Symphyotrichum pratense (= Aster sericeus var. microphyllus). Nostoc commune is abundant on the exposed limestone. Also included here are shaded limestone outcrops with herbaceous vegetation which are dominated by Aquilegia canadensis, Arenaria lanuginosa, Asplenium heterochroum, Carex willdenowii, Chaerophyllum tainturieri, Laportea canadensis, Melica mutica, Oxalis sp., Pachysandra procumbens, Pilea pumila, Polymnia laevigata, Thelypteris kunthii, and Urtica chamaedryoides.

Dynamics:  In the Weches Glades of Texas, soils are shallow, rocky, and basic. These factors tend to inhibit growth of woody vegetation. Outcrops are seepy and saturated during winter and early spring but become hard and dry in the summer. In the Catahoula Barrens of Texas, seasonal droughtiness, shallow soils, aluminum toxicity, and periodic fires are important factors that influence the composition and structure of the vegetation.

In the nepheline syenite outcrops of Arkansas, the absence of fire has modified the flora at some examples, with the buildup of leaf litter and organic matter eliminating the glade herbaceous flora even from shallow soils and rocky areas. Historically, fire would have prevented the establishment of fire-intolerant tree species, reduced or eliminated the organic surface layer, fostered an open canopy with fewer (and larger) trees, and maintained the grass-dominated glade communities. This vegetation responds well to fire management and removal of Juniperus.

Environmental Description:  The vegetation of this group consists of glades and barrens on specific and edaphically unusual substrates in the coastal plains of the southeastern United States. In panhandle Florida limestone examples, the soils and geology has been well documented. In Gadsden County, they occur on limestone outcrops of the Miocene Chattahoochee Formation (Rupert 1990) primarily between the 90- and 120-foot contour lines (27-37 m MSL). In Jackson County, they are found primarily on Oligocene Marianna Limestone (Moore 1955, Means pers. comm. 2007) between the 130- and 150-foot contours (40-46 m MSL). These glades usually occupy areas too small to be distinguished at the scale of county soil survey maps. They may occasionally be shown as rock outcrops within the matrix of the surrounding forest soils. In Gadsden County, these matrix soils are Binnsville soils or Cuthbert, Boswell, and Susquehanna soils on moderate to steep slopes (Thomas et al. 1961b). In Jackson County, the matrix soils are the Oktibbeha variant rock outcrop complex (Duffee et al. 1979).

The Weches Formation is a marine mudstone with abundant fossils of shallow-water organisms and contains appreciable arsenic, which becomes bioavailable due to weathering. The Eocene Claiborne Group of the Texas Gulf Coastal Plain contains alternating clay and quartzose sand units. The Weches Formation in the Nacogdoches area, a transgressive phase of the Claiborne Group, consists of about 20 m of fossiliferous green clay present as sand-sized aggregates ("greensand"), many of which are fecal pellets. The clay is Fe-rich and has been variously described as "mixed-layer montmorillonite" or as glauconite (Ledger and Judy 2003). Soils are mapped as Trawick series (Mollic Hapludalfs).

The habitat of the Catahoula Barrens includes shallow soil and exposed sandstone, which tend to an herbaceous-dominated vegetation expression, as well as zones of deeper soils with open woodland vegetation.

Examples on nepheline syenite are present only in Saline and Pulaski counties, Arkansas, on distinctive, massive outcrops of igneous substrate. Zonal vegetation communities are present around the outcrops. Interior herbaceous-dominated zones can be mesic to wet as springs and small ephemeral streams flow across the rock outcrops and water pools in flat areas. Deeper, more heavily wooded vegetation develops along the flat or slightly sloping outcrop edges.

The Altamaha Grit, now classified by geologists as the Altamaha Formation, outcrops only in southern Georgia; it presumably extends into South Carolina (Huddlestun 1988) but has either been eroded away or remains buried under soil or other types of rock. In addition there are sandstone glades of Panhandle Florida which are dominated by Bigelowia nuttallii.

The calcareous glades of the warm temperate coastal plain of Gadsden and Jackson counties, Florida, and Decatur County, Georgia are found in rather soft, chalky limestone.

The saline examples in Arkansas, Louisiana, and Texas occur on soils with high saline content, which in the most extreme examples are generally not conducive to woody plant growth. Thus, the vegetation forms a mosaic primarily consisting of open herbaceous or shrubby plant communities.

The presence of an intrusive igneous outcrop-forming rock (nepheline syenite) in the Arkansas coastal plain seems anomalous. The plutonic rock intruded into both the coastal plain and the adjacent Ouachitas, but the Ouachita examples no longer have any intact glade and barrens vegetation (assuming they ever did).

Geographic Range: Vegetation of this group is known from at least four distinct regions, but other examples could occur elsewhere in the coastal plains. There are known examples in a localized region of eastern Texas, primarily in San Augustine, Nacogdoches, and Sabine counties; portions of western Louisiana and eastern Texas; the Upper West Gulf Coastal Plain of Saline and Pulaski counties, Arkansas (on nepheline syenite); and the Panhandle of Florida (primarily Gadsden and Jackson counties and adjacent Decatur County, Georgia). In addition, included here are saline glades and barrens of the coastal plain of Arkansas, Louisiana, and Texas.

Nations: US

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




Confidence Level: Moderate

Confidence Level Comments: No Data Available

Grank: GNR

Greasons: No Data Available


Concept Lineage: No Data Available

Predecessors: No Data Available

Obsolete Names: No Data Available

Obsolete Parents: No Data Available

Synonomy: = Catahoula Barrens (Bridges and Orzell 1989a)
> Eastern Redcedar: 46 (Eyre 1980)
> Post Oak - Blackjack Oak: 40 (Eyre 1980)
= Upland Glade (FNAI 1990)
? Upland Glade, Chalky Limestone Glade subtype (FNAI 1992b)

Concept Author(s): M. Pyne, in Faber-Langendoen et al. (2011)

Author of Description: M. Pyne

Acknowledgements: No Data Available

Version Date: 05-12-15

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  • Bridges, E. L., and S. L. Orzell. 1989a. Longleaf pine communities of the West Gulf Coastal Plain. Natural Areas Journal 9:246-263.
  • Coultas, C. L. 1983. Examination of soils associated with four small "limestone glade communities" surrounded by forest in the hills of western Gadsden County. Florida Natural Areas Inventory, Tallahassee.
  • Duffee, E. M., W. J. Allen, and H. C. Ammons. 1979. Soil survey of Jackson County, Florida. USDA Soil Conservation Service in cooperation with the University of Florida Institute of Food and Agricultural Sciences, Agricultural Experiment Stations, Soil Science Department, Gainesville, FL.
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  • FNAI [Florida Natural Areas Inventory]. 1990. Guide to the natural communities of Florida. Florida Natural Areas Inventory and Florida Department of Natural Resources, Tallahassee. 111 pp.
  • FNAI [Florida Natural Areas Inventory]. 1992b. Natural community classification. Unpublished document. The Nature Conservancy, Florida Natural Areas Inventory, Tallahassee. 16 pp.
  • Faber-Langendoen, D., J. Drake, S. Gawler, M. Hall, C. Josse, G. Kittel, S. Menard, C. Nordman, M. Pyne, M. Reid, L. Sneddon, K. Schulz, J. Teague, M. Russo, K. Snow, and P. Comer, editors. 2010-2019a. Divisions, Macrogroups and Groups for the Revised U.S. National Vegetation Classification. NatureServe, Arlington, VA. plus appendices. [in preparation]
  • Foti, Tom. Personal communication. Ecologist [retired]. Arkansas Natural Heritage Commission, Little Rock.
  • Huddlestun, P. F. 1988. A revision of the lithostratigraphic units of the Coastal Plain of Georgia. The Miocene through Holocene. Bulletin 104. Georgia Geologic Survey, Environmental Protection Division, Georgia Department of Natural Resources, Atlanta. 162 pp. plus attachments.
  • Ledger, E. B., and K. Judy. 2003. Elevated arsenic levels in the Weches Formation Nacogdoches County, Texas. [http://www.geology.sfasu.edu/weches.pdf].
  • Leonard, S. W., and W. W. Baker. 1982. Biological survey of the Apalachicola Ravines Biotic Region of Florida. Report to the Florida state office of The Nature Conservancy and to the Florida Natural Areas Inventory, Tallahassee.
  • Marietta, K. L., and E. S. Nixon. 1984. Vegetation of an open, prairie-like community in eastern Texas. Texas Journal of Science 36:25-32.
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  • Moore, W. E. 1955. Geology of Jackson County, Florida. Florida Geological Survey Bulletin No. 37. 101 pp.
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  • Thomas, B. P., H. H. Weeks, and M. W. Hazen, Jr. 1961b. Soil survey of Gadsden County, Florida. USDA Soil Conservation Service in cooperation with the University of Florida Institute of Food and Agricultural Sciences, Agricultural Experiment Stations, Soil Science Department, Gainesville, FL.
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