Physiognomy and Structure: No Data Available

Floristics: Physiognomy varies from nearly closed forest to open woodland with widely spaced trees. The canopy is dominated by more-or-less gnarled specimens of Betula lenta and Quercus montana (= Quercus prinus) generally <20 m tall. Betula lenta is usually the sole dominant of less weathered, steeper, more unstable boulderfield habitats, while a greater variety of trees is often codominant with Betula lenta on more weathered and stable habitats. Other overstory associates that may be important on some sites are Quercus rubra, Nyssa sylvatica, Betula populifolia, Betula papyrifera var. cordifolia, Carya glabra, Tsuga canadensis, and Betula alleghaniensis. The presence of well-preserved, fallen boles indicates that Castanea dentata was important on some boulderfields prior to the arrival of chestnut blight (Fleming and Moorhead 2000). Acer rubrum and Nyssa sylvatica are scattered canopy associates and frequent understory species. The typically open shrub layer contains Acer pensylvanicum, Acer spicatum, Amelanchier arborea, Castanea dentata sprouts, Hamamelis virginiana, Ilex montana, Kalmia latifolia, Menziesia pilosa (at the southern end of the range), and Ribes rotundifolium. The ground layer consists almost entirely of low-statured shrubs, particularly Menziesia pilosa and Vaccinium angustifolium, and/or scattered to abundant vines of Parthenocissus quinquefolia, Vitis spp., Toxicodendron radicans, and Smilax rotundifolia. True herbs are very sparse and restricted to mossy pockets or flat boulders; typical species are Dryopteris marginalis, Polypodium appalachianum, Deschampsia flexuosa, and Danthonia spicata. In the southern portion of the range, Heuchera spp. and Scutellaria saxatilis are characteristic herbs. Bryophyte cover ranges up to 65% in some microhabitats. The rock-tripes Lasallia papulosa and Umbilicaria mammulata, and the foliose species Flavoparmelia baltimorensis, are generally the most conspicuous lichens. The combination of surficial boulder cover and nutrient-poor substrate results in a notably low mean species richness (n = 24 taxa per 400 m2) in Virginia and Maryland plot samples of this type.

Dynamics:  This boulderfield woodland represents a long-term sere in the geomorphic and vegetational progression from exposed, lichen-dominated block fields to fully forested mountain slopes with well-developed mineral soils. In addition to edaphic stresses, trees of these habitats are subject to frequent damage from wind and ice storms. This community often occurs in patch-mosaics with open, lichen-covered boulderfields that lack vascular plants. Boundaries between the boulderfield woodlands and adjacent forests are often obscure, with composition gradually changing along with substrate conditions and soil depth. This type frequently intergrades with several communities of the Mixed Oak / Heath Forests group, especially ~Quercus montana - Quercus rubra / Hamamelis virginiana Forest (CEGL006057)$$ of somewhat sheltered, often very rocky slopes. In Virginia, this association reaches optimal development on sideslopes of linear sandstone and quartzite strike ridges in the Ridge and Valley, and on the western, metasedimentary flank of the northern Blue Ridge. Landsliding and debris avalanches, which generate and regenerate boulderfield environments, are dominant erosional processes in these landscapes (Hack and Goodlett 1960).