Southern Appalachian Forests: Low Elevations

Where is the largest remaining tract of old-growth cove hardwood forest?

• Joyce Kilmer Memorial Forest, Morrisville, NC

The Big Questions

• Why do the southern Appalachians have such high species diversity?

• What factors explain the species composition and structure we see in southern Appalachian forests?

• Do you think it is the ACTUAL ELEVATION that affects species distribution? Which 2 environmental factors would be correlated with elevation?

  • Geography, moisture, temperature, soil type, disturbance, or topographic position? Choose 2.

    • Temperature and moisture.

Lessons from Gregory Ridge Trail

• Each species has a unique niche

• Many niches = many species

• Topographic position affects moisture

What explains high biodiversity in the southern Appalachians?

• Climate (temperature and precipitation)

• Geology

• Disturbance (any event that moves some or all of the existing vegetation)

• Biogeography (both boreal and tropical species)

Whittaker 1956 — Vegetation of the Great Smoky Mountains

• Found that elevation (y axis) and topographic position (x axis) are related

Oak-Pine, Oak-Chestnut Forest

• Low elevation forests (1500-4000 ft)

  • Cove forests

    • rich cove

    • avid cove

  • Montane Oak Forests

  • Pine-oak-heath

• High elevation forests (4000-6684 ft)

  • high elevation red oak forest

  • northern hardwood forest

  • spruce-fir forest

• Elevation, moisture, topography, and soils are major factors that separate these types

Cove forests

• All coves have a concave, bowl-like shape, sheltered slopes (landform)

• Low to mid-elevations (1500-4000 ft)

• Not moisture limited

• Very diverse (but species composition varies)

• Also biologically diverse with many endemics

• Rich coves have fertile soil

  • higher species diversity than acid coves

• Acid coves have acidic soil

Rich cove forest (cove hardwoods)

• low elevation

• most mesic in topographic

• complex structure and layering

• protected, bowl-shaped topography

• highest species diversity = high wildlife diversity

• low disturbance—no fire, protected from wind and storms

• lots of wildflowers!

• Species found here:

  • Yellow-poplar found here (early successional species in the mountains, fast-growing but also long-lived)

  • shortleaf pine is early succession in rest of Piedmont

  • Sugar maple (northern species, source of maple sugar and maple syrup)

  • White ash

  • Black cherry

  • Basswood

Acid cove forest

• Closed canopy and dominant shrub layer

• Protected, bowl-shaped topography

• Lower species diversity than rich coves; higher shrub component

• Disturbance: prior logging, no fire, invasive insects

• Species found here:

  • Eastern hemlock (stream-loving species, decimated by the hemlock woolly adelgid; most old-growth is gone, important streamside habitat species for shading and cooling the water)

  • Sweet birch

  • White pine

  • Rosebay

• The primary environmental difference that results in a rich cove versus an acid cove is soil pH

Montane Oak Forest

• moderate to low elevations

• open slopes

• some low intensity fire

• somewhat open forest

• can have rich understory depending on soil type

• extensive logging history

• 

• Ellicott Rock Wilderness, intersection of NC/SC/GA

• Species found here:

  • American chestnut (once made up 25% of the canopy trees in the Appalachians, now functionally extinct)

  • Rock chestnut oak (most common tree in the mountains, dry forests, middle elevations and below)

  • Scarlet oak (broadly Appalachian, xeric habitats, thin bark)

  • White oak (somewhat fire-tolerant, moist to dry forests, most abundant tree of eastern North America)

  • Northern red oak (mesic forests, low elevation)

  • Mockernut hickory

  • Pignut hickory

  • Red maple (ubiquitous and growing in abundance in the absence of fire)

  • Mountain laurel (wide-spread in eastern NA, xeric forests, heath balds)

• You would expect to find Quercus montana and Quercus coccinea in drier, rockier sites

Pine-oak-heath woodland

• Ridges and other dry, convex topography

• often has thin soils

• lower elevations have more structure and diversity

• canopy is often a woodland than a closed forest

• exposed to wind and sun

• fire adapted; declining without fire as other species outcompete pine

• The understory, which you can see is covered completely with a short shrub with small leaves. This is the Heath part of Pine-Oak-Heath - in this case that heath (in the Ericaceae family, remember) is either Vaccinium (blueberry) or Gaylussacia (huckleberry). Both are really important and widespread shrubs in the southern Appalachians.

• Species found here:

  • Shortleaf pine

  • Virginiana pine

  • Pitch pine (fire-adapted with catastrophic fire with epicormic branching)

  • Table Mountain Pine (fire-adapted to catastrophic fires with serotinous cones)

  • Carolina hemlock (also killed by hemlock woolly adelgid)

  • Mountain laurel (wide-spread in eastern NA, xeric forests, heath balds)

  • Scarlet oak (broadly Appalachian, xeric habitats, thin bark)

• At higher elevations on exposed ridgelines in the southern Appalachians, the canopy gets shorter

Pine-Oak-Heath: Convex ridgelines, exposed

Cove Forest: concave, protected sites

Montane Oak Forest: open slopes