Natural Communities of Virginia - Terrestrial System - Low-Elevation Dry and Dry - Mesic Forests and Woodlands:Low-Elevation Boulderfield Forests and Woodlands

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

Low-Elevation Boulderfield Forests and Woodlands
This group contains open forests and woodlands occupying relatively unweathered boulderfields at elevations below 975 m (3,200 ft). Low-Elevation Boulderfield Forests and Woodlands are known from the northern and central Appalachian regions, extending from Vermont and New Hampshire south to Virginia and West Virginia. In Virginia, these communities are widely scattered throughout the mountains on steep side slopes of ridges, often in zones below large outcrops. They are also common along the Virginia side of the Potomac River Gorge between Washington, D.C., and Great Falls, and locally upstream. Stand composition varies greatly with substrate, aspect, and slope position. Sweet birch (Betula lenta) is usually the sole woody invader of large-block sandstone and quartzite boulderfields, forming pure stands of gnarled, spreading trees. Here, Virginia creeper (Parthenocissus quinquefolia) is sometimes the only low-growing plant able to become established in the deep interstices between boulders. On somewhat more weathered or less blocky boulderfields, chestnut oak (Quercus montana, =Quercus prinus) or mixtures of chestnut oak, northern red oak (Quercus rubra), blackgum (Nyssa sylvatica), and sweet birch, along with a greater diversity of shrubs and herbs, may prevail. Cool, north-facing, sandstone/quartzite boulderfields frequently support some eastern hemlock (Tsuga canadensis) and, locally, disjunct populations of paper birch (Betula cordifolia, = Betula papyrifera var. cordifolia).

On base-rich metabasalt boulderfields of the northern Blue Ridge, basswood (Tilia americana var. americana and var. heterophylla), white ash (Fraxinus americana), and red oak (Quercus rubra) are characteristic trees. Characteristic shrubs and herbs on basic boulderfields include eastern hophornbeam(Ostrya virginiana), red elderberry (Sambucus racemosa var. pubens, = Sambucus pubens), wild hydrangea (Hydrangea arborescens), purple flowering raspberry (Rubus odoratus var. odoratus), Virginia creeper (Parthenocissus quinquefolia), pale jewelweed (Impatiens pallida), marginal wood-fern (Dryopteris marginalis), wood nettle (Laportea canadensis), white-flower leafcup (Polymnia canadensis) and the state-rare herb-robert (Geranium robertianum). Dolomitic or limestone boulderfields support open stands of basswood, sugar maple (Acer saccharum var. saccharum), and yellow buckeye (Aesculus flava), with bladdernut (Staphylea trifolia) abundant in the shrub layer and a variety of mosses, bulblet fern (Cystopteris bulbifera), and other calciphilic herbs forming dense mats on rock surfaces.

Communities in this group are uncommon in Virginia; their classification and distributional status need further assessment. They are floristically distinguished from communities of the High-Elevation Boulderfield Forests and Woodlands group by the preponderance of widely distributed plants and the near-absence of elevation-limited northern and Southern Appalachian species.

References: Fleming (1999), Fleming (2002a), Fleming and Coulling (2001), Fleming and Moorhead (2000), Harrison et al . (1989), Hupp (1983a), Rawinski et al . (1994), Rawinski et al . (1996).

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

	Mesic quartzite rubble supports a relatively diverse assemblage of low-cover herbs under large oaks (Quercus montana and Q. rubra) and tulip-poplar (Liriodendron tulipifera). Jackson Hollow, Bull Run Mountains Natural Area Preserve, Prince William County. Photo: Gary P. Fleming.
	Thin woodland of sweet birch (Betula lenta) occupies a relatively fine quartzite talus deposit on Trayfoot Mountain (Shenandoah National Park). Photo: Gary P. Fleming.
	Sugar maple (Acer saccharum var. saccharum)-dominated boulderfield on basic, intrusive rocks along the Potomac River Gorge, Fairfax County (Turkey Run Park). Photo: Gary P. Fleming.
	Gnarled sweet birch (Betula lenta) trees on deeply piled quartzite talus on the northern Blue Ridge. Near Blackrock, Rockingham County (Shenandoah National Park). Photo: Gary P. Fleming.
	Central Appalachian Basic Boulderfield Forest on metabasalt (greenstone) talus on Saddleback Mountain, Greene County (Shenandoah National Park). Canada leafcup (Polymnia canadensis) and wood nettle (Laportea canadensis) dominate a sparse herb layer under an overstory of white ash (Fraxinus americana) and basswood (Tilia americana var. americana). Photo: Gary P. Fleming.

REPRESENTATIVE COMMUNITY TYPES:
Four classified community types belonging to this group are conceptually sound and reasonably well supported by plot data, but may be subject to minor nomenclatural refinements if future data analysis warrants. Wider geographic sampling of this group is needed, particularly in the Cumberland Mountains and southern Blue Ridge. Click on any highlighted CEGL code below to view the global USNVC description provided by NatureServe Explorer.

Acer (nigrum , saccharum) – Tilia americana – (Aesculus flava) / Staphylea trifolia / Cystopteris bulbifera Forest
Appalachian Calcareous Boulderfield Forest
USNVC: = CEGL006020
Global/State Ranks: G4?/S3?
Betula lenta – Quercus montana – Quercus rubra / Menziesia pilosa Woodland
Central Appalachian Acidic Boulderfield Forest (Sweet Birch Type)
USNVC: = CEGL006565
Global/State Ranks: GNR/S3S4
Quercus rubra – Quercus montana / Parthenocissus quinquefolia – Vitis aestivalis var. bicolor / Dryopteris marginalis – Aralia nudicaulis Forest
Central Appalachian Acidic Boulderfield Forest (Lower Blue Ridge / Foothills Mixed Oak Type)
USNVC: no equivalent
Global/State Ranks: GNR/SNR
Tilia americana – Fraxinus americana / Acer pensylvanicum – Ostrya virginiana / Parthenocissus quinquefolia – Impatiens pallida Forest
Central Appalachian Basic Boulderfield Forest
USNVC: = CEGL008528
Global/State Ranks: G3/S3?

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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)