Highelevation red oak forest

Distinguishing Features

High-elevation red oak forest differs from all other high-elevation forests in that northern red oak makes up 75 percent or more of the canopy.

Introduction

Northern red oak (Quercus rubra) grows as a canopy species in a variety of communities in the mountain and piedmont regions. While it shares dominance with other canopy species in most communities, northern red oak is the overwhelming dominant in some high mountain areas. High-elevation red oak forest occurs on dry to mesic slopes and ridgetops at elevations between 3,500 and 5,500 ft. with well-drained, rocky, acidic soils. The forest varies from being a closed canopy of large well-formed trees on middle and upper slopes to an open canopy of gnarled, stunted trees (called oak orchards) on ridges exposed to high winds and frequent ice storms.

Vegetation

In addition to northern red oak, other canopy trees include chestnut oak (Q. montana) and red maple (Acer rubrum), with small patches of red spruce (Picea rubens) at higher elevations. American chestnut (Castanea dentata) was once a canopy dominant or co-dominant before an introduced fungus (commonly known as the chestnut blight) decimated it in the early twentieth century. Today, this once magnificent species persists as root sprouts and slowly rotting trunks.

The understory has low to moderate coverage with small trees or shrubs such as bigfruit hawthorn (Crataegus macrosperma), smooth serviceberry (Amelanchier laevis), mountain holly (Ilex montana), and witch hazel (Hamamelis virginiana). Shrubs in the heath family (Ericaceae) are common, including evergreen species such as mountain laurel (Kalmia latifolia), rosebay (Rhododendron maximum), and Catawba rhododendron (R. catawbiense), as well as deciduous species such as flame azalea (R. calendulaceum) and blueberries (Vaccinium spp.). The herbaceous layer is often dense and fairly diverse in "oak orchards" as an open canopy increases the amount of light reaching the forest floor. Common herbs include speckled wood lily (Clintonia umbellulata), white snakeroot (Ageratina altissima), bigleaf aster (Eurybia macrophylla), whorled loosestrife (Lysimachia quadrifolia), and lousewort (Pedicularis canadensis). A diverse mixture of herbaceous plants grows under deciduous shrubs, with fewer herbs under the denser shade of evergreen shrubs.

Seasonal Aspects

Spring-flowering trees include black locust (Robiniapseudoacacia), a fast-growing tree with deeply furrowed bark, paired thorns at the base of compound leaves, and white pea-like flowers in drooping clusters. If a thorn appears to move it's likely a locust treehopper, a sap-sucking insect that likes to play hide and seek. Bigfruit hawthorn, a small thicket-forming tree also has thorns (long, sharp ones!) and white to pink flowers in dense flat-topped clusters. In late spring, the brightly colored tubular flowers of flame azalea light up the forest understory. Subtler are the succulent, tumor-like green galls on its stem tips, which typically appear from early spring through mid-late summer. Alternate leaf dogwood (Cornus alternifo-lia), a multistemmed shrub with widely spreading horizontal branches, produces small white flowers in flat-topped clusters in spring and dark blue berry-like fruits on red stalks in late summer and fall. The inconspicuous, wind-pollinated late-winter and early spring flowers of American and beaked hazelnut (Corylus americana and C. cornuta) develop into edible nuts in late summer and fall. Squirrels, blue jays, and other wildlife species very quickly harvest the tasty nuts enclosed within large leafy bracts.

Carrion flower (Smilax herbacea), an herbaceous climbing vine, derives its name from the carrion-like odor associated with its numerous yellow-green flower clusters (umbels). Shiny carrion flies often hang out near the flowers, perhaps looking for (but not finding) a place to lay their eggs. Another herbaceous climbing vine is wild yam (Dioscorea villosa). Its tiny yellow-green spring flowers develop into showy, three-winged fruits in late summer and fall. Other spring-flowering herbs include lousewort, Canada mayflower (Maianthemum canadense), and whorled loosestrife. Bumblebees frequently visit lousewort's yellowish to reddish brown tubular flowers in tightly packed heads. Canada mayflower forms dense mats of short-stemmed plants bearing 1-3 broadly ovate leaves. Its tiny white flowers develop into translucent red berries in late summer. Whorled loosestrife is a relatively tall plant whose solitary yellow flowers on long stalks emerge from whorled leaves in late spring and summer.

Summer-flowering species include rosebay, leather flower (Clematis viorna), bigleaf aster, and occasionally, the root sprouts of American chestnut. Bumble bees forage for nectar on the white to pale-pink flower clusters of rosebay as well as the striking urn-shaped red-purple flowers of leather flower, an herbaceous climbing vine. Bigleaf aster has large, heart-shaped, basal leaves with upright shoots whose pale purple ray flowers surround yellow disk flowers that become reddish with age. In open, sunny areas, the thin shoots of the American chestnut sometimes accumulate sufficient resources to produce elongate clusters of small, fragrant cream-colored flowers, but rarely are fruits with viable nuts produced.

In late summer and fall, mountain holly, bigfruit hawthorn, and wake robin (Trillium erectum) produce conspicuous reddish fruits, whereas alternate leaf dogwood, blackberries (Rubus spp.), carrion flower, and speckled wood lily produce clusters of dark blue-black fruits. The leaves of northern red oak, often filled with circular holes made by June beetles (a nocturnal buzzing insect), turn a deep scarlet color in autumn. Providing contrast are the butter-yellow autumn leaves of striped maple (Acerpensylvanicum) and witch hazel.

Red oaks and white oaks. Oaks are divided into 2 distinct groups, red oaks and white oaks, based on characteristics associated with their leaves and acorns. The red oak group includes species such as northern red oak, scarlet oak (Q. coccinea), and black oak (Q. velutina), whereas white oak (Q. alba), chestnut oak, and post oak (Q. stellata) are members of the white oak group. Leaves of the red oak group have bristles on their leaf tips and leaf lobes; leaves of the white oak group don't. Acorns in the white oak group mature in one summer and germinate the following autumn, shortly after they drop from the trees. Acorns in the red oak group take 2 summers to mature, and because an overwintering period is required, germinate in spring, rather than autumn. Acorns in the red oak group are rich in fats and have high tannin concentrations serving as a chemical defense compound. Acorns in the white oak group are lower in lipids and have lower concentrations of tannins. The higher tannins found in the acorns of the red oak group presumably reflect their greater vulnerability to seed predators, as they remain dormant for a longer period prior to germinating. Differences in acorn chemistry also influence the behavior of seed predators/dispersers. Squirrels eat the acorns of the white oak group immediately, or they excise the seedling embryo (thereby preventing germination and loss of food energy) prior to burial. Acorns of the red oak group are generally buried undamaged in autumn and consumed in winter. Unrecovered acorns often germinate and form seedlings, but few survive to become trees.

Distribution

High-elevation red oak forest is found at higher elevations in the mountains of Virginia, North Carolina, Tennessee, and Georgia, particularly on broad ridges with southerly aspects. Where spruce-fir forest is absent, high-elevation red oak forest may extend to the highest peaks.

Dynamics

High-elevation red oak forest is susceptible to disturbance by high winds, ice storms, and fires. On exposed ridges, winds gusting at more than 100 mph bend, twist, and blow down trees. Ice and snow build up and break off branches, exposing trees to attack by insects and fungi. Lightning splits and injures trees and periodically ignites low-intensity surface fires. Periodic disturbance facilitates forest regeneration by opening up the canopy and increasing the amount of light reaching the forest floor. Because northern red oak is relatively light demanding, occasional disturbance plays a critical role in its persistence as a canopy dominant. The loss of American chestnut as a canopy dominant in the 1930s provided an unusual opportunity for northern red oak to recruit new individuals into the canopy. As a result, higher-elevation forests dominated by northern red oak currently cover a larger area than they did prior to the chestnut blight in the 1930s.

Conservation Aspects

Most high-elevation red oak forests have been logged. Logging, coupled with chestnut blight in the early twentieth century, opened up the forest, thereby providing an opportunity for shade-intolerant, opportunistic species such as black locust, tulip tree (Liriodendron tulipifera), and yellow birch (Betula alleghaniensis) to get established. Past disturbance and fire exclusion have increased the density of both heath shrubs and fast-growing understory species such as red maple, which can hinder northern red oak regeneration. An infestation of gypsy moths is an additional threat as the caterpillars have led to repeated defoliation and widespread mortality in oak-dominated forests of the central and northern Appalachians.

SUGGESTED READING

Crow, T. R. 1988. Reproductive Mode and Mechanisms for Self-Replacement of Northern

Red Oak (Quercus rubra)—A Review. Forest Science 34:19-40. DeLapp, J. 1978. Gradient Analysis and Classification of the High Elevation Red Oak

Community of the Southern Appalachians. M.S. thesis, North Carolina State University, Raleigh.

Stephenson, S. L., and H. S. Adams. 1989. The High-Elevation Red Oak (Quercus rubra) Community Type in Western Virginia. Castanea 54:217-29.

HIGH-ELEVATION RED OAK FOREST: CHARACTERISTIC PLANTS

Trees

ABUNDANT SPECIES

Quercus rubra

Northern red oak pp. 259-60

OCCASIONAL TO LOCALLY ABUNDANT SPECIES

Acer pensylvanicum Acer rubrum Betula alleghaniensis Castanea dentata Crataegus macrosperma

Striped maple Red maple Yellow birch American chestnut Bigfruit hawthorn p. 221 p. 222 pp. 226-27 pp. 231-32 p. 236

Quercus montana

Chestnut oak

pp. 258-59

Robinia pseudoacacia

Black locust

pp. 260-61

Shrubs

OCCASIONAL TO LOCALLY ABUNDANT SPECIES

Cornus alternifolia

Alternate leaf dogwood

p. 279

Corylus cornuta

Beaked hazelnut

pp. 280-81

Gaylussacia ursina

Bear huckleberry

p. 284

Hamamelis virginiana

Witch hazel

pp. 285-86

Ilex montana

Mountain holly

pp. 288-89

Kalmia latifolia

Mountain laurel

pp. 291-92

Rhododendron calendulaceum

Flame azalea

p. 301

Rhododendron catawbiense

Catawba rhododendron

pp. 301-2

Rhododendron maximum

Rosebay

pp. 302-3

Rubus allegheniensis

Allegheny blackberry

p. 310

Viburnum lantanoides

Witch hobble, Hobblebush

p. 321

Herbs

OCCASIONAL TO LOCALLY ABUNDANT SPECIES

Ageratina altissima

White snakeroot

pp. 328-29

Athyrium asplenioides

Southern lady fern

p. 340

Carex pensylvanica

Pennsylvania sedge

pp. 343-44

Clematis viorna

Leather flower

p. 352

Clintonia umbellulata

Speckled wood lily

pp. 353-54

Conopholis americana

Squawroot, Cancer root

p. 355

Dennstaedtia punctilobula

Hayscented fern

p. 360

Dioscorea villosa

Wild yam

pp. 363-64

Dryopteris campyloptera

Mountain wood fern

p. 366

Eurybia macrophylla

Bigleaf aster

p. 372

Galax urceolata

Galax, Skunkweed

pp. 374-75

Laportea canadensis

Wood nettle

p. 395

Lysimachia quadrifolia

Whorled loosestrife

pp. 399-400

Maianthemum canadense

Canada mayflower

pp. 400-401

Oclemena acuminata

Whorled aster

p. 409

Osmunda claytoniana

Interrupted fern

pp. 413-14

Pedicularis canadensis

Lousewort, Wood betony

p. 419

Smilax herbacea

Carrion flower

pp. 440-41

Solidago curtisii

Curtis's goldenrod

p. 443

Thelypteris noveboracensis

New York fern

pp. 451-52

Trillium erectum

Wake robin

p. 457

Rare Plants

'Eutrochium purpureum

Purple node Joe Pye weed

tPrenanthes roanensis

Appalachian rattlesnake root

= plant not included in the species profiles (Part IV)

= plant not included in the species profiles (Part IV)

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