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Ecological site PX136X00X400

Triassic basin upland woodland, expansive clay, seasonally wet and dry

Accessed: 04/29/2024

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General information

Provisional. A provisional ecological site description has undergone quality control and quality assurance review. It contains a working state and transition model and enough information to identify the ecological site.

MLRA notes

Major Land Resource Area (MLRA): 136X–Southern Piedmont

This area is in North Carolina (29 percent), Georgia (27 percent), Virginia (21 percent), South Carolina (16 percent), and Alabama (7 percent). It makes up about 64,395 square miles (166,865 square kilometers). (Ag Bulletin 296)

The northeast-southwest trending Piedmont ecoregion comprises a transitional area between the mostly mountainous ecoregions of the Appalachians to the northwest and the relatively flat coastal plain to the southeast. It is a complex mosaic of Precambrian and Paleozoic metamorphic and igneous rocks with moderately dissected irregular plains and some hills. (EPA Ecoregions descriptions)

ADD APPROPRIATE ECOREGION DESCRIPTION(S)

Classification relationships

A PROVISIONAL ECOLOGICAL SITE is a conceptual grouping of soil map unit components within a Major Land Resource Area (MLRA) based on the similarities in response to management. Although there may be wide variability in the productivity of the soils grouped into a Provisional Site, the soil vegetation interactions as expressed in the State and Transition Model are similar and the management actions required to achieve objectives, whether maintaining the existing ecological state or managing for an alternative state, are similar. Provisional Sites are likely to be refined into more precise group during the process of meeting the APPROVED ECOLOGICAL SITE DESCRIPTION criteria.

This PROVISIONAL ECOLOGICAL SITE has been developed to meet the standards established in the National Ecological Site Handbook. The information associated with this ecological site does not meet the Approved Ecological Site Description Standard, but it has been through a Quality Control and Quality Assurance processes to assure consistency and completeness. Further investigations, reviews and correlations are necessary before it becomes an Approved Ecological Site Description.

Ecological site concept

This community occurs most commonly on mafic igneous rocks found in the Triassic basins in the Piedmont of the southeastern United States. Examples may be found on flat uplands where diabase (and related rocks such as gabbro) form dikes or sills close to the surface and subsequent soil development has been affected. Typically, these areas develop dense subsurface "hardpans" and shrink-swell properties that limit plant rooting depth. Thus, vegetation often has a somewhat stunted and open canopy dominated by Quercus stellata and Quercus marilandica. Other typical canopy species include Carya carolinae-septentrionalis, Carya glabra, Fraxinus americana, Quercus alba, Quercus phellos, Pinus virginiana, Pinus echinata, and others. Typical understory species include Juniperus virginiana var. virginiana, Cercis canadensis var. canadensis, Diospyros virginiana, Vaccinium arboreum, Ulmus alata, and Chionanthus virginicus. Shrubs may be sparse or dense, with Viburnum rafinesquianum (= var. rafinesquianum), Viburnum prunifolium, Viburnum rufidulum, and Vaccinium stamineum typical. The most common herbs are Danthonia spicata and Schizachyrium scoparium. Other herbs may include Piptochaetium avenaceum, Clematis ochroleuca, Sericocarpus linifolius (= Aster solidagineus), Hieracium venosum, Hieracium gronovii, Hypericum hypericoides, Symphyotrichum dumosum (= Aster dumosus), Oenothera fruticosa, Lespedeza spp., and Solidago spp. Cladonia spp. are typically present and sometimes common and conspicuous. The woodland structure is maintained by extreme edaphic conditions or by fire.

Associated sites

PX136X00X430	Triassic basin upland forest, dry
PX136X00X420	Triassic basin upland forest, moist

PX136X00X430

Triassic basin upland forest, dry

PX136X00X420

Triassic basin upland forest, moist

Table 1. Dominant plant species

Tree	(1) Quercus stellata (2) Carya glabra
Shrub	Not specified
Herbaceous	(1) Schizachyrium scoparium (2) Piptochaetium avenaceum

Legacy ID

F136XY400NC

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Physiographic features

Most of MLRA 136 is in the Piedmont Upland Section of the Piedmont Province of the Appalachian Highlands. A very small part of the MLRA, in central North Carolina, is in the Atlantic Plain Division. A very small part in the Roanoke, Virginia, area is on the eastern edge of the Blue Ridge Province of the Appalachian Highlands. This MLRA is a rolling to hilly upland with a well-defined drainage pattern. The original plateau has been dissected by streams, resulting in narrow to fairly broad upland ridgetops and short slopes. Valley floors are very narrow, and stream terraces are minor. Elevation ranges from 330 to 1,310 feet (100 to 400 m), increasing gradually from south to north.

Geology:
Precambrian and Paleozoic metamorphic and igneous rocks underlie almost all of this MLRA. The dominant metamorphic rock types include biotite gneiss, schist, slate, quartzite, phyllite, and amphibolite. The dominant igneous rock types are granite and metamorphosed granite. Some gabbro and other mafic igneous rocks also occur, and diabase dikes are not uncommon. The Carolina Slate terrane occurs just east of an imaginary centerline in this MLRA. It consists of metamorphic rocks with some metavolcanics and metasediments. Scattered graben basins, which are bounded by faults where the ground between the faults has dropped down, occur from South Carolina to south of Charlottesville and Richmond, Virginia. These basins have Triassic and Jurassic siltstone, shale, sandstone, and mudstone. River valleys have recent alluvium and few terraces.

Figure 1. EPA Level IV Ecoregion map.

Table 2. Representative physiographic features

Landforms	(1) Hill (2) Interfluve (3) Ridge
Flooding frequency	None
Ponding frequency	None
Slope	2 – 8%
Water table depth	46 – 76 cm
Aspect	Aspect is not a significant factor

Climatic features

The average annual precipitation is 37 to 45 inches (940 to 1,145 millimeters) at the northern end of this area, is 45 to 60 inches (1,145 to 1,525 millimeters) at the southern end, and is as much as 75 inches (1,905 millimeters) in a small, high-elevation area in northeastern Georgia. The precipitation generally is evenly distributed throughout the year. It is lowest in autumn. Most of the rainfall occurs as high-intensity, convective thunderstorms during the growing season. Significant moisture also comes from the movement of warm and cold fronts across the MLRA from November to April. High amounts of rain can occur during hurricanes at the same time of the year. Snowfall typically is light. The average annual temperature is 53 to 64 degrees F (12 to 18 degrees C). The freeze-free period averages 230 days and ranges from 185 to 275 days. Both the mean annual temperature and length of the freeze-free period increase from north to south and with decreasing elevation.

Table 3. Representative climatic features

Frost-free period (average)	174 days
Freeze-free period (average)	198 days
Precipitation total (average)	1,219 mm

Bar

Line

Figure 2. Monthly precipitation range

Bar

Line

Figure 3. Monthly average minimum and maximum temperature

Figure 4. Annual precipitation pattern

Figure 5. Annual average temperature pattern

Climate stations used

(1) FOREST CITY 6 SW [USC00313150], Forest City, NC
(2) SHELBY 2 NNE [USC00317845], Shelby, NC
(3) BROOKNEAL [USC00441082], Brookneal, VA
(4) TYE RIVER 1 SE [USC00448600], Amherst, VA
(5) HICKORY FAA AP [USW00003810], Hickory, NC
(6) YADKINVILLE 6 E [USC00319675], East Bend, NC
(7) CROZIER [USC00442142], Maidens, VA
(8) MARTINSVILLE FLTR PLT [USC00445300], Martinsville, VA
(9) WASHINGTON DC DULLES AP [USW00093738], Chantilly, VA
(10) GASTONIA [USC00313356], Gastonia, NC
(11) LENOIR [USC00314938], Lenoir, NC
(12) APPOMATTOX [USC00440243], Appomattox, VA
(13) PALMYRA 3S [USC00446491], Palmyra, VA
(14) LOUISA [USC00445050], Louisa, VA
(15) ROCKY MT [USC00447338], Rocky Mount, VA

Influencing water features

The extent of the major Hydrologic Unit Areas (identified by four-digit numbers) that make up this MLRA is as follows: Edisto-Santee (0305), 18 percent; Chowan-Roanoke (0301), 14 percent; Apalachicola (0313), 10 percent; Pee Dee (0304), 10 percent; Ogeechee-Savannah (0306), 10 percent; Alabama
(0315), 9 percent; Altamaha-St. Marys (0307), 9 percent; Lower Chesapeake (0208), 9 percent; Neuse-Pamlico (0302), 5 percent; Cape Fear (0303), 5 percent; and Potomac (0207), 1 percent. Some of the major rivers in this MLRA are, from north to south, the Roanoke, Cape Fear, Savannah, Altamaha, Chattahoochee, and Alabama Rivers. These rivers typically form within the Piedmont Province and flow east and south across the Coastal Plain Province and empty into the Atlantic Ocean or Gulf of Mexico.

Soil features

Soils associated with this ecological site occur in the mesic soil temperature regime of MLRA 136. This soil temperature regime is defined as: The mean annual soil temperature is 8 degree C or higher but lower than 15 degrees C, and the difference between mean summer and mean winter soil temperatures is 6 degrees C or more either at a depth of 50 cm below the soil surface or at a densic, lithic, or paralithic contact, whichever is shallower. These Alfisols weathered from Triassic Basin have a restrictive layer between 50 and 100 cm (20-40 inches) and are well to somewhat poorly drained. The combination of the presence of a lithic or paralithic contact and high potential shrink-swell, rooting depth and available water are limited for plant growth.

Table 4. Representative soil features

Surface texture	(1) Silt loam (2) Sandy loam (3) Fine sandy loam
Soil depth	38 – 102 cm
Surface fragment cover <=3"	0 – 10%
Available water capacity (0-101.6cm)	10.16 – 20.32 cm
Calcium carbonate equivalent (0-101.6cm)	0%
Electrical conductivity (0-101.6cm)	0 mmhos/cm
Sodium adsorption ratio (0-101.6cm)	0
Soil reaction (1:1 water) (0-101.6cm)	4.7 – 5.8
Subsurface fragment volume <=3" (Depth not specified)	0 – 8%

Ecological dynamics

This ecological site represents a range of habitats that are generally small and insular, occur over basic or mafic rock, and have soil rooting depths too limited to support forest trees and thus are very dry in character. In some cases this type is a consequence of montmorillonitic clay soils (shrink-swell hardpans) derived from mafic rocks of the Triassic Basin. In other cases open woodland occurs on steep rock outcrops of mafic rock which have as much as 70% surface substrate cover of exposed bedrock, and these soils have moderately high levels of calcium and magnesium. Finally, both in north-central North Carolina (especially Granville County) and in the South and North Carolina Piedmont Deep River Triassic Basin (closer to Charlotte) are soils which derived from mafic igneous rock and with high or very high shrink-swell potential.

State and transition model

Custom diagram

Standard diagram

Figure 6. state and transition model

More interactive model formats are also available. View Interactive Models

Supporting information

Other references

Edwards, L., J. Ambrose, and L.K. Kirkman. 2013. The Natural Communities of Georgia. The University of Georgia Press. Athens and London.

Evans, R.E. and G.P. Fleming. 2007. Association Detail Report: CEGL003714 [last revised 29May2007]. United States National Vegetation Classification. Federal Geographic Data Committee, Washington, D.C.

Environmental Protection Agency (EPA). 2004. Level III and IV Ecoregions of EPA Region 4. U.S. Environmental Protection Agency, National Health and Environmental Effects Research Laboratory. Western Ecology Division, Corvallis, Oregon. Scale 1:2,000,000.

Fleming, Gary P. and Karen D. Patterson. 2013. Natural Heritage Report 13-16. Natural Communities of Virginia: Ecological Groups and Community Types. Virginia Department of Conservation and Recreation, Division of Natural Heritage, Richmond, Virginia. 36 pages.

NatureServe. 2013. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia. Available http://www.natureserve.org/explorer. (Accessed May 24, 2013).

Nelson, John B. 1986. The natural Communities of South Carolina: Initial Classification and Description. South Carolina Wildlife and Marine Resources Department.

Schafale, M. P. 2012. Classification of the natural communities of North Carolina, 4th Approximation. North Carolina Department of Environment, Health, and Natural Resources, Division of Parks and Recreation, Natural Heritage Program, Raleigh.

Schafale, M. P., and A. S. Weakley. 1990. Classification of the natural communities of North Carolina. Third approximation. North Carolina Department of Environment, Health, and Natural Resources, Division of Parks and Recreation, Natural Heritage Program, Raleigh. 325 pp.

Spira, Timothy P. 2011. Wildflowers and Plant Communities of the Southern Appalachian Mountains and Piedmont. The University of North Carolina Press. Chapel Hill.

United States Department of Agriculture, Natural Resources Conservation Service, 2006. Land Resource Regions and Major Land Resource Areas of the United States, the Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook 296.

Wharton, C.H. 1978. The natural environments of Georgia. Bulletin 114. Georgia Department of Natural Resources. Atlanta.

Contributors

Dee Pederson

Rangeland health reference sheet

Interpreting Indicators of Rangeland Health is a qualitative assessment protocol used to determine ecosystem condition based on benchmark characteristics described in the Reference Sheet. A suite of 17 (or more) indicators are typically considered in an assessment. The ecological site(s) representative of an assessment location must be known prior to applying the protocol and must be verified based on soils and climate. Current plant community cannot be used to identify the ecological site.

Author(s)/participant(s)
Contact for lead author
Date
Approved by
Approval date
Composition (Indicators 10 and 12) based on	Annual Production

Indicators

Number and extent of rills:
Presence of water flow patterns:
Number and height of erosional pedestals or terracettes:
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
Number of gullies and erosion associated with gullies:
Extent of wind scoured, blowouts and/or depositional areas:
Amount of litter movement (describe size and distance expected to travel):
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
Functional/Structural Groups (list in order of descending dominance by above-ground annual-production or live foliar cover using symbols: >>, >, = to indicate much greater than, greater than, and equal to):

Dominant:

Sub-dominant:

Other:

Additional:
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
Average percent litter cover (%) and depth ( in):
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
Potential invasive (including noxious) species (native and non-native). List species which BOTH characterize degraded states and have the potential to become a dominant or co-dominant species on the ecological site if their future establishment and growth is not actively controlled by management interventions. Species that become dominant for only one to several years (e.g., short-term response to drought or wildfire) are not invasive plants. Note that unlike other indicators, we are describing what is NOT expected in the reference state for the ecological site:
Perennial plant reproductive capability:

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