Old Growth Oak Forests in North Georgia

I’ve written a lot lately about Georgia’s grassland communities, but my favorite types of environments in the state are oak forests and oak-pine woodlands.  Believe it or not, ecologists do discern the difference between forest and woodland.  A forest is defined as a tree dominated community with a canopy coverage greater than 80%, whereas a woodland is defined as a tree dominated community with a canopy coverage of between 50%-80%.  A savannah community has less than 50% canopy coverage; a prairie has grass but no trees at all. Old growth oak forests and woodlands are nearly extinct in the piedmont region where they were once the dominant ecological communities.  However, Jess Riddle surveyed the Blue Ridge Mountains in north Georgia and found approximately 84 sites that show little to no human disturbance.  Most are located in inaccessible areas where road building and agriculture were not practical.  It’s possible some of these sites were logged long ago, but he couldn’t find any evidence of this at many of them, and the age of the trees suggests these sites are virgin old growth forests.

In Georgia oak forests and oak-pine woodlands grow at elevations of 3500 feet and below.  The majority of the sites Jess Riddle surveyed (55) can be classified as acidic-dry communities.  The dominant trees are rock chestnut oak (Quercus montana) and scarlet oak (Quercus concinea).  A dense layer of ericaceous shrubs including mountain laurel and blueberry shade out tree saplings and grass.  Shrubs in the ericaceous family prefer acidic soils.  Twenty of the old growth sites host moister soils and support forests of northern red oak, white oak, tulip, pignut hickory, Fraser magnolia, and hemlock.  Some of these moister forests grade into rich cove forests.  Most old growth sites have chestnut sprouts and debris, showing that this species was once an important component before the chestnut blight wiped them out.  Mafic forests are another type of forest.  They are influenced by chemicals that weather from rock, and these environments are  more open than other types of forest.  White oak and hickory dominate mafic forests.

Double Spring Knob

Spaniard Mountain

Spaniard Mountain located in northeastern Georgia may be 1 of the more impressive sites surveyed.  I couldn’t find any ground level photos of this mountain on google images, so it must not be visited very often.  It is 2 miles from the nearest road.  The map above indicates a trail of some sort.  Jess Riddle saw no signs of human disturbance here and found some ancient trees in this tract.  He cored 1 white oak and discovered it was 303 years old.  Four chestnut oaks ranged in ages from 196-296 years old.  The canopy is dominated by northern red oak.  Rhododendron, mountain laurel, and huckleberry (which he described as “thick”) grew in the understory.

Double Spring Mountain also revealed no evidence of human disturbance.  Four cores of white oaks showed the trees ranged in ages between 175-210 years old while a northern red oak was 215 years old.  Scarlet oak, chestnut sprouts, mountain laurel, dogwood, and blackberry were abundant.

Gap phase dynamics is the ecological mechanism that shapes low to mid elevation oak forests.  Disease, insects, draught, windstorms, fire, and lightning kill trees and create gaps in the canopy for shade intolerant species such as oaks to grow.  The 20th century policy of fire suppression  has led to forests dominated by shade tolerant species such as tulip, red maple, locust, and white pine.  When there are fewer oaks, acorn production is reduced and wildlife populations decline.  More frequent fire converts oak forests to oak-pine woodlands.  Scarlet oak, black oak, blackjack oak, and southern red oak grow with shortleaf pine, pitch pine, Virginia pine, and table mountain pine in these environments.  There are also ericaceous shrub layers in oak-pine woodlands but with grass, fern, and composite wildflowers as well.  Jess Riddle found a shortleaf pine at 1 of these oak-pine woodland sites that was 212 years old.

Jess Riddle took note of the fauna he encountered in these old growth forests.  He saw game trails, bear sign, white tail deer, wild hogs, a flying squirrel, ruffed grouse, a timber rattle snake, and bald faced hornet nests.  Birds requiring deep forest environments such as hairy woodpeckers, scarlet tanagers, wood thrushes, ovenbirds, and black and white warblers prevail here.

White Oak estimated to be between 250-300 years old in Alpharetta, Georgia.  A whole forest of trees this age occurs on Spaniard Mountain.

Chestnut oak.  The leaves resemble those of the chestnut (Castanea dentata). Note how large the acorns are. Nevertheless, scarlet oaks, white oaks, red oaks, and black oaks produce more acorns than chestnut oaks.

Bald faced hornet (Dolichouespula maculata) nest.  What a natural work of beauty.

Ruffed Grouse.  Early successional forests located next to montane old growth oak forests are about the only place you can see this species in Georgia.

Best chance of seeing a black bear or bear sign in Georgia is to hike a trail in these old growth oak forests.

I’d be just as excited to see a flying squirrel as a black bear.

Low to mid elevation oak forests in north Georgia have existed on these sites in the Blue Ridge Mountains for at least 11,000 years and began gradually replacing semi-boreal conifer forests about 15,000 years ago.  Pollen records indicate spruce and pine forests dominated this area from about 29,000 BP-14,000 BP, albeit with a few brief interuptions.  Between 60,000 BP-30,000 BP climate fluctuated dramatically and rapidly, and the response of various tree species likely lagged behind climate change.  Spruce and pine grew better during cold phases because they are better adapted to drier, windier, and icier environments with lower atmospheric CO2 levels.  During warm phases of climate, oaks and other broadleafed trees shade conifers out.  The animal and plant composition of transitional periods between warm and cold climate phases would have been interesting to observe.  Wildlife was probably most abundant when oaks were in the process of replacing boreal conifers or vice versa because they would h0st birds and mammals  found in both types of environments.  A mix of boreal coniferous and broadleafed forests was probably the norm in north Georgia during the mid-Wisconsinian.  Our present stable interglacial climate phase is more of an aberration.

Reference:

Riddle, Jess

“Selected Statistics on Old Growth Stands in the Chattahoochee National Forest”

Georgia Forest Watch Document

http://www.gafw.org/pdf_files/chattahoochee_og_site_characteristics.pdf

Tags: acorn production, bald faced hornet nest, bear sign, chestnut oak, Double Spring Knob, ericaceous shrub, flying squirrel, Jess Riddle, low to mid elevation oak forests, oak-pine woodlands, old growth oak forests, ruffed grouse, Spaniard Mountain