Mixed Hardwoods

Appalachian valley

Mixed hardwood forests are widespread in mountain landscapes. They occupy sites below 4000 ft elevation that are intermediate on gradients of fertility, moisture, and exposure to sun and wind. This forest type is the most abundant in these landscapes and is important for maintaining connectivity among forested habitats. Mixed hardwood forests consist of oaks, hickories, maples, ash, sourwood, and black gum. Some species of oak is usually present as a canopy dominant. Mixed hardwood forests sustain growth of commercially valuable trees for furniture manufacturing, and their mast producing trees help support wildlife. Yellow poplar may be present, especially at sites where the canopy has been opened by natural or anthropogenic disturbances. White pine is also a common component and is especially abundant in some areas such as the Blue Ridge Escarpment in the Carolinas and Georgia. Occasional fires may be important for regenerating stands of oaks and hickories. These forests often have open understory and shrub layers. The shrub component of these forests may include rosebay rhododendron (Rhododendron maximum), mountain laurel (Kalmia latifolia), flame azalea (R. calendulaceum), blueberry (Vaccinium spp.) and huckleberry (Gaylusaccia spp.).

Violets

Before it was decimated by an exotic pathogenic fungus, the American chestnut (Castanea dentata) was a prominent component of these forest. Stands of chestnut have been replaced by a variety of tree species, especially chestnut oak, red oak, red maple and hickories. Chestnut trees spanned a wide range of moisture conditions. In sheltered sites, this species was replaced by more mesophytic species while more xerophytic species replaced it on dry slopes and ridges (Woods and Shanks 1959).

The mixed hardwood community has been subdivided into several forest types based on canopy dominants: e.g., red oak-pignut hickory, chestnut oak-American chestnut, red oak-American chestnut, white oak-chestnut (Stephenson and others 1993). While there is a great deal of overlap in the position of species along environmental gradients, the dominant canopy species are somewhat segregated with respect to moisture and landform. At low elevations, white oaks often dominate in valley bottoms and gentle slopes, while chestnut oak forests become more common on middle to upper slopes. American holly (Ilex opaca) is often present at low-elevation sites. Southern red oak (Q. falcata) and post oak (Q. stellata) may be present at the lowest elevations. North- and east-facing slopes have more northern red oaks, white ash, American beech and occasional representatives of cove forests such as basswood. South- and west-facing slopes at moderate elevations have more xeric conditions and are dominated by oak-hickory forest types that include mixtures of black oak, chestnut oak, red oak, black gum and mockernut, pignut, red pignut, and shagbark hickories. At higher elevations, red oaks become more common in the transition to the northern hardwood community.

Red maple

Representative tree species of mixed hardwood forests

• Chestnut oak (Quercus prinus)
• White oak (Quercus alba)
• Black oak (Quercus velutina)
• Northern red oak (Quercus rubra)
• Pignut hickory (Carya glabra)
• Red pignut hickory (Carya ovalis)
• Mockernut hickory (Carya tomentosa)
• Flowering dogwood (Cornus florida)
• American holly (Ilex opaca)
• White ash (Fraxinus americana)
• American beech (Fagus grandifolia)
• Fraser magnolia (Magnolia fraseri)
• Cucumber-tree (Magnolia accuminata)
• Black gum (Nyssa sylvatica)
• Red maple (Acer rubrum)
• Sourwood (Oxydendrum arboreum)
• White pine (Pinus strobus)
• Black cherry (Prunus serotina)