Mountain / Piedmont Basic Woodlands
This group is represented by deciduous and mixed woodlands of xeric, rocky habitats over mafic substrates such as diabase, gabbro, metabasalt (greenstone), and amphibolite. A few examples occur in habitats underlain by base-rich granite, calcareous shale, and calcareous sandstone. Occurrences in Virginia are widely and locally scattered throughout the mountains and Piedmont foothills, often occurring in patch-mosaics with exposed outcrop barrens. They are most frequent (but still very local) in metabasalt districts of the northern Blue Ridge. Habitats are situated on south- to west-facing slopes with numerous outcrops and shallow, rocky soils that are dry but relatively fertile, with moderate to high levels of calcium and magnesium.
Although oaks (Quercus spp.) are frequent (sometimes co-dominant) components, these woodlands are more often dominated by variable mixtures of white ash (Fraxinus americana) and hickories (Carya spp.), often with eastern red cedar (Juniperus virginiana) or Virginia pine (Pinus virginiana) as a major associate. Trees are usually stunted and form an open or sparse overstory. Typical understory trees and shrubs include eastern redbud (Cercis canadensis var. canadensis), eastern hophornbeam (Ostrya virginiana), ninebark (Physocarpus opulifolius var. opulifolius), slippery elm (Ulmus rubra), aromatic sumac (Rhus aromatica var. aromatica), hackberries (Celtis occidentalis and Celtis pumila), hoptree (Ptelea trifoliata var. trifoliata), and pasture rose (Rosa carolina var. carolina). These woodlands contain a surprisingly diverse array of herbaceous graminoids and forbs; a few of the more widespread, representative species are cliff muhly (Muhlenbergia sobolifera), elm-leaved goldenrod (Solidago ulmifolia var. ulmifolia), bottlebrush grass (Elymus hystrix), Pennsylvania sedge (Carex pensylvanica), woodland sunflower (Helianthus divaricatus), Appalachian phacelia (Phacelia dubia var. dubia), hoary mountain-mint (Pycnanthemum incanum var. incanum), smooth blue asters (Symphyotrichum laeve and Symphyotrichum concinnum), Virginia spiderwort (Tradescantia virginiana), and narrow-leaved vervain (Verbena simplex). Unusual stands that occur on concave slopes at two sites have herb layers dominated by river-oats (Chasmanthium latifolium).
Mountain / Piedmont Basic Woodlands are similar to dry limestone forests and woodlands but generally lack the latter's characteristic calciphilic species such as chinkapin oak (Quercus muehlenbergii), black maple (Acer nigrum), Carolina buckthorn (Frangula caroliniana), and American beakgrain (Diarrhena americana). Most Virginia stands of Mountain / Piedmont Basic Woodland represent a single, state and globally rare community type. There are few threats, although the shrub coralberry (Symphoricarpos orbiculatus), introduced from farther west, is a troublesome invasive in some stands. Additionally, the dominant white ash component of these woodlands is currently suffering extensive mortality from outbreaks of the insect pathogen Emerald Ash Borer.
References: Coulling and Rawinski (1999), Fleming (2002a), Fleming and Coulling (2001), Fleming et al. (2007), Rawinski et al . (1996).Click here for more photos of this ecological community group.
© DCR-DNH, Gary P. Fleming.