Natural Communities of Virginia - Terrestrial System - Low-Elevation Rock Outcrops and Barrens: Ultramafic Barrens

The Natural Communities of Virginia
Classification of Ecological Community Groups
SECOND APPROXIMATION (Version 2.2)

Ultramafic Barrens
These grasslands occupy soils developed from serpentinite, soapstone, talc-tremolite schist, and other ultramafic rocks. Only two occurrences of this very rare vegetation are known in Virginia: one in the southern Piedmont (Franklin County) and one in The Glades region of the southern Blue Ridge plateau (Grayson County). Habitats are relatively gentle uplands with harsh soils containing high levels of magnesium and iron. Ultramafic Barrens, along with the closely related Ultramafic Woodlands, are the only terrestrial communities documented in Virginia that grow in soils with Ca:Mg ratios < 1.

Vegetation of the two sites differs considerably. The dry, rocky Piedmont habitat is dominated by little bluestem (Schizachyrium scoparium), prairie ragwort (Packera plattensis = Senecio plattensis), and glade wild quinine (Parthenium auriculatum). Noteworthy associates include northern dropseed (Sporobolus heterolepis), Menge's fame-flower (Talinum mengesii), Pitcher's stichwort (Minuartia patula var. patula), and Kate's Mountain clover (Trifolium virginicum).

The southern Blue Ridge habitat features considerable seasonal wetness and a peculiar mixture of upland and wetland species, but is treated here as a community of the Terrestrial System. Little bluestem and indian grass (Sorghastrum nutans) are the dominant grasses, while white colicroot (Aletris farinosa), narrowleaf whitetop aster (Sericocarpus linifolius), narrow-leaved mountain-mint (Pycnanthemum tenuifolium), and balsam ragwort (Packera paupercula, = Senecio pauperculus) are characteristic forbs. Coastal plain disjuncts such as crossleaf milkwort (Polygala cruciata), twisted yellow-eyed-grass (Xyris torta), pitted nutrush (Scleria muhlenbergii), yellow screwstem (Bartonia virginica), and Virginia meadow-beauty (Rhexia virginica) are numerous in seasonally wet gravel.

Along with unusual edaphic conditions, fire probably played a key role in maintaining natural ultramafic barrens in the pre-settlement landscape. Both community types are endemic to Virginia, are extremely rare, and occur in patch-mosaics with similarly rare Ultramafic Woodlands. Major threats include fire exclusion, woody species encroachment, grazing, agriculture, and development.

Click on the images below to open a larger image in a separate window.

A remnant ultramafic barren on talc-tremolite-chlorite schist in Franklin County. Photo: Tom Rawinski.

REPRESENTATIVE COMMUNITY TYPES:
Each of the two classified community types is represented by a single plot sample. The likelihood of discovering additional sites for this vegetation or obtaining additional quantitative data is very small. Click on any highlighted CEGL code below to view the global USNVC description provided by NatureServe Explorer.

Schizachyrium scoparium – Packera plattensis – Parthenium auriculatum – Talinum mengesii Herbaceous Vegetation (PROVISIONAL)
Southern Piedmont Ultramafic Barren
USNVC: =CEGL006084
Global/State Ranks: G1/S1
Endemic
Schizachyrium scoparium – Sorghastrum nutans – Aletris farinosa – Packera paupercula Herbaceous Vegetation
Southern Blue Ridge Ultramafic Barren
USNVC: =CEGL004999
Global/State Ranks: G1/S1
Endemic

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The Natural Communities of Virginia Classification of Ecological Community Groups SECOND APPROXIMATION (Version 2.2)

The Natural Communities of Virginia
Classification of Ecological Community Groups
SECOND APPROXIMATION (Version 2.2)