The Natural Communities of Virginia
Classification of Ecological Community Groups
SECOND APPROXIMATION (Version 2.2)
Calcareous Fens and Seeps
This group includes shrubby and herbaceous wetlands of calcareous hillside or foot-slope spring seeps and seepage zones in small stream bottoms. These small-patch wetlands are widely scattered in carbonate rock districts of western Virginia, primarily in valleys of the Ridge and Valley province. Habitats typically have irregular or hummock-and-hollow microtopography, with areas of muck and abundant gravel or travertine marl deposits in the seepage rills. Soils, which are typically derived from underlying limestone or dolomite, are slightly to moderately alkaline with high calcium levels. Strictly defined, fens are minerotrophic wetlands with organic soils > 40 cm deep. Because they usually have only superficial organic soil layers, most of the Virginia communities in this group are technically seeps, although we retain the term fen due to its wide application to various base-rich seepage wetlands in the southeastern United States; see Weakley and Schafale (1994) for additional discussion.
The vegetation of these wetlands is often a patch-mosaic of shrubs and herbaceous openings. Common shrubs include willows (
Salix spp.), smooth alder (
Alnus serrulata), swamp rose (
Rosa palustris), alder buckthorn (
Rhamnus alnifolia), and chokeberries (
Aronia arbutifolia) and
Aronia prunifolia). Herbaceous species that are more or less diagnostic of calcareous fens or seeps include several sedges (
e.g .,
Carex flava ,
Carex hystericina ,
Carex interior,
Carex schweinitzii,
Carex suberecta ,
Carex tetanica), showy lady's-slipper (
Cypripedium reginae), small-headed rush (
Juncus brachycephalus), bog twayblade (
Liparis loeselii), large-leaved grass-of-parnassus (
Parnassia grandifolia), swamp lousewort (
Pedicularis lanceolata),
shining ladies'-tresses (
Spiranthes lucida), and hairlike beakrush (
Rhynchospora capillacea). Other common herbs include bristly-stalk sedge (
Carex leptalea ssp.
leptalea), royal fern (
Osmunda regalis var. spectabilis), and golden ragwort (
Packera aurea = Senecio aureus). The ecological factors that keep fens and seeps open are not well understood, and many examples appear to be threatened by shrub and tree invasion. Ditching, grazing, and introduced weeds are additional threats to these naturally rare wetlands, most of which are unprotected and are high priorities for conservation.
References: Artz and Krouse (1967), Carr (1939), Fleming (1999), Fleming and Coulling (2001), Fleming and Van Alstine (1999),
Ogle (1989).
Click on the images below to open a larger image in a separate window.
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Central Appalachian Calcareous Shrub Fen / Seep along Peters Mill Run in the Massanutten Mountains, where calcareous
shales provide the requisite soil chemistry. Characteristic plants at this site include smooth alder (Alnus serrulata), royal
fern (Osmunda regalis var. spectabilis), and rigid sedge (Carex tetanica).
Photo © Gary P. Fleming. |
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Eastern indian-paintbrush (Castilleja coccinea), golden ragwort (Packera aurea), and field horsetail
(Equisetum arvense) dominate a Ridge and Valley calcareous seep in Montgomery County.
Photo: Irvine Wilson. |
REPRESENTATIVE COMMUNITY TYPES:
About half of the known occurrences in Virginia have been documented with plot data, resulting in the classification of two community types. The second of these (Ridge and Valley Calcareous Fen / Seep) is supported by only two plots and must be considered provisional pending data collection from a wider sample of related vegetation.
Click on any highlighted CEGL code below to view the global USNVC description provided by NatureServe Explorer.
- Alnus serrulata / Osmunda regalis var. spectabilis Carex tetanica Carex leptalea Shrubland
Central Appalachian Calcareous Shrub Fen / Seep
USNVC:
= CEGL008408
Global/State Ranks:
G1?/S1
Endemic
- Packera aurea Carex interior Carex hystericina Parnassia grandifolia Herbaceous Vegetation (PROVISIONAL)
Ridge and Valley Calcareous Fen / Seep
USNVC:
~CEGL004944
Global/State Ranks:
G2G3/S1
