Name:
Pinus virginiana - Pinus pungens - Pinus rigida Woodland & Barrens Group
Reference:
NatureServe Biotics 2019
Description:
Vegetation of this group encompasses predominantly evergreen woodlands and forests occupying very exposed, convex, often rocky south- and west-facing slopes, ridge spurs, crests, and clifftops in the Central Appalachians, Southern Ridge and Valley and Southern Blue Ridge, as well as distinctive shale barrens of low to mid elevations in the Central and Southern Appalachians. They typically occur at moderate to upper elevations (450-1200 m [1500-4000 feet]), with the more southerly examples at the higher elevations. In the Southern Blue Ridge, this group is best developed above 700 m (2300 feet) in elevation, but some examples may be found at lower elevations. The underlying rock is acidic and sedimentary or metasedimentary (e.g., quartzites, sandstones and shales). The soils are very infertile, shallow and droughty. A thick, poorly decomposed duff layer, along with dead wood and highly volatile ericaceous shrubs, creates a strongly fire-prone habitat. Most examples are dominated by <i>Pinus pungens</i>, often with <i>Pinus rigida</i> and/or <i>Pinus virginiana</i>, and occasionally <i>Tsuga caroliniana</i>. The canopy is usually patchy to open, but areas of closed canopy may be present, especially where <i>Tsuga caroliniana</i> is prominent, or where fire has been absent. The shrub layer may be well-developed, with <i>Gaylussacia baccata, Vaccinium pallidum</i>, or other acid-tolerant species most characteristic. Herbs are usually sparse but may include <i>Pityopsis graminifolia</i> and <i>Tephrosia virginiana</i>. Fire is a very important ecological process in this group. Frequent, low-intensity fires coupled with periodic severe fires is one factor that determines the occurrence of this vegetation rather than hardwood forests under natural conditions. The pines may be able to maintain dominance due to edaphic conditions, such as very shallow soil or extreme exposure in some areas, which can produce sustained drought conditions, but most sites appear eventually to succeed to oak dominance in the absence of fire. Fire is also presumably a strong influence on vegetation structure, producing a more open woodland canopy structure and more herbaceous ground cover.<br /><br />In floristically distinctive shale barrens examples, the exposed aspects, parent material with high levels of toxic metals, and lack of soil create extreme conditions for plant growth. Vegetation is mostly of a woodland physiognomy, but may include large open areas of sparse vegetation. The dominant trees are primarily <i>Quercus montana</i> and <i>Pinus virginiana</i>. On higher-pH shale barrens, which are less common, the primary trees include <i>Juniperus virginiana</i> and <i>Fraxinus americana</i>, but these are placed in a different group. Shale barrens endemics are diagnostic in the herb layer. The substrate includes areas of solid rock as well as unstable areas of shale scree, usually steeply sloped. The fully exposed areas are extremely dry. These barrens are high in endemic species.
Accession Code:
urn:lsid:vegbank.org:commConcept:39974-{015456A0-3D6D-4351-A215-E45C8F1444C7}
Plot-observations of this Community Concept:
0
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