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

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The Vanishing Chinkapin (Castania pumila)

Photo from google images of chinkapin nuts in a burr.

The chinkapin, a shrubby relative of the American chestnut and not to be confused with the similarly named chinkapin oak (Quercus muhlenberger), used to be locally common, growing on the tops of rocky hills in the piedmont region of the southeast and in the undergrowth of open pine savannahs on the coastal plain.  The early explorer, John Lawson, reported the trees as so common that hogs fattened on the nuts.  He described the nuts as smaller, rounder, and sweeter than those of its relative, the chestnut.  Most sources state that it was the better tasting of the two.  William Bartram found chinkapin growing in association with chestnuts and chestnut oaks (Quercus prinus) on the tops of rocky piedmont hills, a forest type that contrasted with that of the surrounding area which was mostly an oak forest but in the valleys between the rocky hills a much richer forest of black walnut, beech, hackberry, tulip, and sycamore grew.  Moist creek bottoms and richer soils kept the latter area from burning, but the thin dry soils at the tops of rocky hills endured frequent fires.  Oak and chinkapin thrive in fire prone sites because they’re shade intolerant and need open areas to grow.

Most of the jobs I’ve had in the Augusta, Georgia area have taken me to just about every neighborhood in Richmond and Columbia Counties.  I used to survey lawns for Orkin Lawn Care, and I worked for many years as a route manager for the Augusta Chronicle. While working I, of course, took note of the vegetation (ecology has always held a great interest for me), and I’ve never seen a chinkapin.  Botanists warn the chinkapin is in decline for a number of reasons: fire suppression, chestnut blight, and suburban development.  Without fire, shade tolerant trees begin to dominate, and chinkapin can’t grow in the shade.  The chestnut blight completely destroyed the once common chestnut forests.  The chinkapin is also susceptible but is better able to survive because it is a shrub that resprouts and can produce a crop of nuts before it dies back again from the disease.  Still, the blight reduces overall nut production.

The chestnut blight was a disaster for the ecosystem.  Chestnuts and chinkapins were important sources of food for wildlife.  Now, trees such as tulip, which produce no mast, have replaced chestnuts.  They may be beautiful trees but animals can’t eat beauty.  I think the lack of chestnuts explains why I saw almost no wildlife on my trip to the Smoky Mountains National Park last summer (see my blog entry “Gatlinburg, Tennessee: Tale of a Tourist Trap Nightmare” which is I believe in the June 2010 archives).

The chinkapin has two interesting adaptations that help it survive as a species.  It germinates quickly in the fall.  The nut ripens from September to November, and they produce heavily–up to 1500 nuts per bush, beginning when they’re just six years old.  Squirrels disperse the species by burying the highly valued food, but the chinkapins foil the squirrels when they germinate immediately.  After they’ve become a seedling, the squirrel can’t utilize them.  Fall germination prevents animals from destroying the entire progeny, but by producing a nut with high food value, they motivate the squirrels to disperse them.  The other adaptive characteristic is its ability to resprout vigorously.  Fire may kill the main trunk, but chinkapin will resprout and form thickets.  Deer also find chinkapin a favored food and will browse down the main trunk, causing the shrub to resprout and create thickets.  Their thickets provide great cover and food for turkey and grouse.

Fossil evidence shows that turkey and grouse were quite common in upland Georgia during the Pleistocene–both left abundant specimens at Ladds and Kingston Saltpeter Cave in Bartow County.  Two studies of sediment cores in Georgia found that chestnut/chinkapin made up about 2%  of the pollen spectrum during the Pleistocene.  Both sites (Nodoroc and Grays Reef) date to about 30,000 BP.  Chinkapin surely was a common component of the open oak and pine savannahs so prevalent then.  Its ability to resprout and fall germinate is an ancient adaptation to survive fire and megafauna foraging.  The more such animals as mastodon, horse, llama, and deer browsed, the more this shrub would bounce back and form thickets ideal for bird life.

The Indians used to cook chinkapin and hickory nuts with their venison in well-rounded stews.  Chinkapins are a nice starchy substitute for bread or potatoes; hickory nuts provided a nice oily substitute for butter.  Chestnuts, unlike most other nuts, are primarily a carbohydrate based food, rather than a fatty form of sustenance.  They’re sweet and bready and act as a laxative.  I hate to buy expensive imported European chestnuts when I think how abundant and cheap American chestnuts and chinkapins used to be.