Xeric Oak-Pine

Xeric oak-pine forests occupy dry, exposed ridges at moderate to low elevations (<4000 ft). They can also occur on the upper portions of exposed, south- and west-facing slopes. These forests are common in the edges of major river valleys and where the mountain ranges of the Southern Blue Ridge Province border the Piedmont and Ridge and Valley Provinces. The balance between deciduous and coniferous canopies depends on the moisture status and disturbance history of the stands. Sites that are more exposed, have shallower soils, or have been recently disturbed tend to have more pines. Fires may be important for maintaining some species. The driest locations are covered by xeric pine-heath forests.

The canopy trees of this community include xerophytic oaks and pines. The oak component consists principally of scarlet oak and chestnut oak, southern red oak, and occasionally black oak. The pines include pitch, shortleaf and Virginia pine. Black gum is often present, but individual trees can appear stunted and slow growing in comparison with the growth of this species in the mixed hardwood forest. Common shrubs include mountain laurel (Kalmia latifolia), trailing arbutus (Epigaea repens), blueberry (Vaccinium spp.) and huckleberry (Gaylussacia spp). Horsesugar (Symplocos tinctoria) is common along the Blue Ridge Escarpment and outlying mountain ranges. Galax (Galax urceolata), an evergreen herb, can form continuous groundcover under canopy trees, and mountain laurel can occur in substantial thickets. Otherwise, the herbaceous cover tends to be sparse.

Outcrops

Rock outcroppings may occur in stands of xeric oak-pine forest. Rock outcrops harbor some of the most specialized and rare species in the southern highlands. These species have adaptaions for surviving the extremely dry conditions of these microsites. The chemistry, particularly pH, of the underlying parent rock often determines what species will be present. For example, rocks having a nearly neutral pH support stands of red cedar (Juniperus virginiana) and rare species such as mockorange (Philadephus hirsutus) and shooting-star (Dodecatheon meadia). In contrast, acidic rocks support stands of ericaceous shrubs and small ferns such as mountain spleenwort (Asplenium montanum). Pines or Carolina hemlock (Tsuga caroliniana), rather than cedar, form the coniferous component of these communities. Rock surfaces are the site of primary succession and support lichens and mosses. Newly formed soil accumulates in depressions and crevasses and supports vascular plants. In the Southeastern U.S., rock outcrop communities on the periphery of the mountains have a large number of endemic herbaceous species (Quarterman and others 1993).

Representative tree species of xeric oak-pine forests:

• Chestnut oak (Quercus prinus)
• Scarlet oak (Quercus coccinea)
• Southern red oak (Quercus falcata)
• Black oak (Quercus velutina)
• Pitch pine (Pinus rigida)
• Virginia pine (Pinus virginiana)
• Shortleaf pine (Pinus echinata)
• White pine (Pinus strobus)
• Black gum (Nyssa sylvatica)
• Red maple (Acer rubrum)
• Sourwood (Oxydendrum arboreum)