Ramble Report November 3, 2022
Leader
for today’s Ramble:
Linda
Author
of today’s Ramble report: Linda. Comments, edits, and suggestions for
the report can be sent to Linda at Lchafin@uga.edu.
Insect
and fungi identifications: Don Hunter, Bill Sheehan
Link to Don’s Facebook album for this Ramble. All the photos that appear in this report, unless otherwise
credited, were taken by Don Hunter. Photos may be enlarged by clicking them
with a mouse or tapping on your screen.
Number of Ramblers today: 26
Today’s
emphasis: Changing leaf color and
other transitions from summer to fall in a Piedmont Oak-Hickory-Pine forest.
Reading: Catherine Chastain
brought in a poem: “Morning Talk” by Jarod K. Anderson, from his book, Love
Notes from the Hollow Tree (2022).
Morning
Talk
My
arm brushed a blue spruce on a gray hike.
I
spoke in a voice made of sparrows, stinging the quiet like sparks from a kicked
fire.
That
sudden sound hung a question on the air,
but
I did not answer.
I
knew that to answer would end a discussion
I
dearly want to stretch on
for
a lifetime.
Show and Tell:
 |
| The ginkgos near the arbor are turning their glorious gold. |
Gary brought a fallen branch from a
hickory. One end of the branch is cut straight across
smoothly as if it were cut by clippers. It had been girdled by one of several species
in the Longhorn Beetle family (Cerambycidae) known as Twig Girdlers and Twig Pruners.
In late summer or fall, a female chooses a twig ¼ – ½ inch in diameter on which
to lay her eggs and chews a deep groove around it, leaving only a thin strand
of wood in the center and killing the twig, which soon breaks off. She lays her
eggs under the bark at the girdled point on the fallen twig. When the eggs hatch, the larvae feed
on the dead wood and live inside the twig until the following summer. The
larvae begin pupating late in the following summer; within two weeks, the adults emerge,
mate, and begin the cycle again with a new round of girdling and egg-laying.
 |
| Twig girdled by a Longhorn Beetle |
Announcements/Interesting
Things to Note:
On
Wednesday, November 9, the Friends of the State Botanical Garden of Georgia are hosting the
annual Johnstone Lecture, this year featuring Dr. Cassandra Quave, a medical
ethnobotanist on the faculty of Emory University Medical School, and author of
“Plant Hunter: A Scientist’s Quest for Nature’s Next Medicines.” The book
chronicles her global search for plant compounds that may address the threat of
antibiotic-resistance microbes, as well as her struggles as a female field
researcher with a disability. The lecture will be held in the Visitor Center at
the Botanical Garden at 6:30 p.m., with a reception and book signing held at
7:30 p.m in the Museum. This event is free and open to the public, but pre-registration
is required here. https://botgarden.uga.edu/event/johnstone-lecture-2/
Gary
mentioned that the Oconee Rivers Audubon Society meets monthly, first Thursday
of each month, September through May, at 7:00 p.m., at Sandy Creek Nature
Center. There is always an interesting speaker.
Richard
extended an invitation to a garden walk and wood-fired pizza oven dinner at his
place on November 13 at around 4:30 p.m. His address is: Please RSVP at richard2191@charter.net.
There
is an interesting exhibit now at the Georgia Museum of Art on campus called “Longleaf
Lines.” The artist is Kristin Leachman; the exhibit is part two of her “Fifty
Forests” project, which documents the self-organizing patterns in trees in all 50
U.S. states. The show will be up till Sunday, Feb 12, 2023.
A lunar eclipse will be visible in the early hours of Tuesday, November 8.
Today’s
Route: After crossing the prairie, we entered the Blue Trail where it intersects
both the Green and White Trails. We wound through the successional and Oak-Hickory-Pine forests
along the Blue Trail and then turned north onto the service road that follows a
ridge east to the intersection with the Green Trail, which we took back to the
prairie, from where we returned to the Visitor Center.
How and
Why Leaves Change Color
Here in Georgia, we live at the southern end of the great Eastern Deciduous Forest, a renowned hot spot of biological diversity, especially when it comes to trees. In
the Piedmont of Georgia, we have more than 200 tree species, many of which contribute to a colorful show in the fall. In
New England, there are fewer tree species; the color displays are more intense than ours but shorter. The more diverse the forest,
the longer and more varied the colorful display.
 |
|
| Piedmont mixed hardwood forest (photo by Lee Shearer) |
Leaves change color because
of the presence of four types of pigments: chlorophylls,
carotenoids, tannins, and anthocyanins.
The first three of these
are present in leaves throughout the growing season – green chlorophyll is the pigment that facilitates
photosynthesis. Things begin to change as the nights get longer and the temperatures
drop, triggering the breakdown of chlorophyll. As the green pigment disappears,
the ever present yellow and golden pigments – carotenoids – are revealed, along with the tannins
that give leaves a brown or tan color at the end of fall.
 |
| Hickories are giving a golden show right now. (photo by Gary Crider) |
Leaves
undergo another change in response to longer, cooler nights – they prepare to
drop their leaves. Two special layers of cells form at the point where the leaf
stalk connects to the twig; this is called the abscission zone. One layer, the
layer nearer the twig, becomes impregnated with wax, forming a protective layer
between the twig and the outer world once the leaf falls. The other layer, the
layer at the base of the leaf stalk, breaks down, loosening the leaf’s
connection to the twig.
Sugars trapped in the leaf
when the waxy layer forms are converted to the fourth pigment, anthocyanin.
Anthocyanin is found throughout the plant world in the red of apples, the
blue of blueberries, and purple of eggplant (and so on). Some of the most
brilliant fall colors in the Piedmont are due to anthocyanin in the leaves of Sourwood, Sweet Gum, Dogwood, Red Maple, Black Gum, Dogwood, and Chalk Maple.
 |
| Sourwood |
 |
| Sweet Gum (photo by Lee Shearer) |
 |
| Flowering Dogwood (Photo by James Gaither) |
 |
| Chalk Maple (photo by Lee Shearer) |
How
leaves change color is pretty well understood. But doesn’t it seem like a lot
of trouble just to brighten up leaves that are only days away from dropping to the forest floor? Which brings us to the question of why leaves change colors in the fall. Why don’t trees simply let their leaves fall to the
forest floor in the fall? Is there adaptive
value to the color change? Much to my surprise, scientists do not know. “Several
hypotheses have emerged to explain the evolution of autumn colors [but] the
adaptive value of this color change remains a mystery,” wrote a group of scientists
in 2009 and, as best I can tell, they haven’t figured it out yet.
One theory is that, as the tree
canopy thins and more light penetrates the crown of the tree, anthocyanin
acts as sunscreen, protecting the leaves as they slowly wither. This
protection allows the leaf to stay functional long enough to withdraw the
maximum amount of nutrients – nitrogen, phosphorus, iron, and manganese – back
into the twigs and down into the roots, where they are stored.
Another theory relies on the fact that the color red is a warning
signal to some animals. Responding to this red flag, egg-laying aphids avoid
trees with red leaves. Since aphids can damage a tree during egg deposition by introducing
viruses and bacteria, a tree that
can produce red leaves in the fall has an adaptive advantage.
Yet another theory is that
red leaves act as a billboard to migrating birds: tasty berries are here – Exit Now! Take a
look at Flowering Dogwood (above), Black Gum and Virginia Creeper (below). Their leaves turn red when
their berries are ripe. Eating these berries on the fly, birds disperse
the tree’s seeds across a wider range.
 |
| Black Gum (photo by M. B. Gargiullo) |
 |
| Virginia Creeper (photo by Jacki-dee) |
Whichever theory, or
theories, is proven correct, I am confident it will be more beautifully complex
than I ever dreamed.
 |
| Color is also happening on the forest floor. Crane Fly Orchid leaves emerge in the fall, and by flipping the leaf over, you can see the lustrous purple of the lower leaf surface. |
What is the best weather
for producing brilliant leaf color?
The best combination of
weather for a spectacular show of red, orange, and purple is a wet spring
and summer followed by warm, sunny fall days and cool nights. Warm fall
days and moist soils ensure that leaves produce lots of the sugars that are converted
to anthocyanin. Cool nights trigger the formation of the abscission layer that
traps the sugars and pigments in the leaf. Since the yellow pigment in the
leaves of Hickories, Redbuds, and Tulip Trees is revealed primarily in response
to longer nights, these shades are revealed regardless of weather. However, if
there is a severe drought or cold snap, all leaves are liable to turn brown and fall
without going through a colorful phase.
Oak – Hickory – Pine: Matrix Forest of the Piedmont
The Blue
Trail and the Service Road that crosses the trail pass through classic Piedmont
Oak-Hickory-Pine forest. This forest covers most of the uplands at the Garden,
except for the prairie in the right-of-way and the cultivated gardens.
 |
| Scarlet Oak is a typical species of the Oak-Hickory-Pine forest. The base of the trunk often has a crumbly, black appearance, while the upper trunk usually has narrow, vertical pale stripes. |
 |
| Scarlet Oak leaves have deep, C-shaped sinuses and the base of the blade is more or less perpendicular to the leaf stalk. |
 |
| Persimmon is typical of the Oak-Hickory-Pine forest, although this twisted trunk is unusual. This tree is a “female,” with a few orange fruits left on the upper branches. |
 |
|||||
| Lots of Mockernut Hickory husks without their nuts were seen on the ground today. |
Gary reported that his grandmother
used to make “delicious persimmon-nut bread with Mockernut Hickory nuts, the
biggest and the best.” And, inspired by forester Dan Williams, Gary also learned
to make hickory nut milk, using Mockernuts “because I had hundreds of
them. After removing the thick husks, I didn’t finely crush the shells, simply used vise-grips to
crack open the nuts. No need to pick out the meats! Just boil for a long
time to extract the “milk” and a marvelous room-filling aroma.” For
a similar traditional Cherokee method for making hickory milk, watch this sweet video.
 |
| Shagbark Hickories are found at the Garden only in the areas with amphibolite bedrock. |
 |
| Yellow-bellied Sapsuckers seem partial to Hop Hornbeam, another tree like Shagbark Hickory that is associated with amphibolite. |
Shortleaf Pines
Both Loblolly and Shortleaf Pines are common here. The presence of Loblolly indicates that it has been a long time since this forest burned; Loblolly isn’t very fire-tolerant until it’s old and its bark thickens.
On the other hand, Shortleaf is adapted from a young age to frequent fire. Within the first three
months after sprouting from a seed, its stem turns and grows horizontally for a couple of
inches then turns again, this time straight up, creating what’s called a “basal
crook.” Dormant buds form at the base of the crook, and are protected by the overlying
soil. These buds will sprout if the upper stem is killed by fire or other damage. This gives
Shortleaf an advantage over Loblolly or other pine species that do not have the
ability to re-sprout after fire. This once abundant tree is disappearing from the southern landscape; the Shortleaf Pine Initiative, a coalition of private landowners, conservationists, and land-managing agencies are working to turn that around.
 |
|
Basal crook |
 |
| Shortleaf sprouts arise from the base of a stem killed by fire. (photo by Holly Campbell) |
Although lightning- or human-set fires may have historically burned across this ridge, re-introducing fire to this part of the Garden will be difficult and take a high level of expertise. There are decades-worth of fuel built up here, including a thick layer of needle and leaf litter, many downed trees and branches, and pine needles draping branches. Smoke management would be an issue, too, with the Loop and campus nearby.
 |
| “Needle drape” on low branches can act as ladder fuel, carrying fire dangerously into tree tops. |
 |
| The thick bark plates of mature Loblolly Pines make them fire-resistant. This tree’s bark is encrusted with decades of lichens, another indicator that this forest has never burned. |
 |
| Trametopsis cervina has no common name, but Don, Bill, and Joan refer to it as “coffee and cream.” |
 |
| Pore surface ofTrametopsis cervina |
 |
| Mycena species growing out of a decorticated trunk |
 |
| Conifer-cone Mushroom grows only on pine cones, in this case a Loblolly cone. |
 |
| Smoked Oysterling mushrooms |
 |
| False Turkey Tail fungi Don bruised the pore surface (underside), eliciting the yellow color that confirmed the species, Stereum lobatum. |
 |
| Turkey Tail fungi |
 |
| Pore surface of the Turkey Tail fungi |
Round Bullet Gall wasps have a complicated life cycle, involving two entirely different galls. The galls we saw today likely contain only female wasps; males are produced later. Here‘s some great information on this gall-former.
 |
| Round Bullet Gall |
 |
| Round Bullet Gall with near adult Cynipid wasp |
 |
| Round Bullet Gall Wasp Note those huge red eyes! (photo by Bill Sheehan) |
Myrna made the most exciting find today: a group of Giant Bark
Aphids being tended by red ants on a young Beech trunk. Giant Bark
Aphids are the largest aphid in the U.S.
Giant Bark
Aphids feed on a variety of trees, including Basswood, Hickory, Oak, Pecan, Sycamore,
Walnut and Wax Myrtle. Athenians most likely know of this insect and its
relatives – or anyway, their excreta –
by finding a black moldy coating on their cars and outdoor furniture in late
summer and early fall. Like most aphids, Giant Bark Aphids excrete large quantities
of clear, sweet liquid, called “honeydew,” as they feed. Honeydew builds up on
surfaces below trees and is soon colonized by Sooty Mold, which grows on the
sugar-rich honeydew. The mold can damage the finish on cars and furniture and
harms plants by reducing the amount of sunlight that leaves absorb, thus interfering with photosynthesis.
For more information, see this link. And for more amazing images of Giant Bark Aphids,
click here.
 |
| Giant Bark Aphid (photo by Bill Sheehan) |
What about those ants, swarming over and around the aphids? Turns
out that honeydew is not only rich in sugars, but also proteins and other
compounds that are nutritious to other insects. These ants were likely
consuming the honeydew, while also protecting the aphids from parasitic insects.
(Enlarge photos by clicking them
with a mouse or tapping on your screen.)
Postscript: Here’s a great map of the Garden’s
trails
OBSERVED SPECIES:
Sourwood Oxydendrum arboreum
Purple Passionflower Passiflora incarnata
Sweet Gum Liquidambar styraciflua
Broomsedge Andropogon virginicus
Bushy Bluestem Andropogon glomeratus
Silver Plume Grass Erianthus alopecuroides syn. Saccharum alopecuroides
Yellow Indian Grass Sorghastrum nutans
Red Maple Acer rubrum
Mayberry Vaccinium elliottii
Daddy Longlegs/Harvestmen Family Opiliones
Pignut Hickory Carya glabra
Winter Creeper Euonymous fortunei
Mockernut Hickory Carya tomentosa
Cranefly Orchid Tipularia discolor
Trametopsis cervina (no common name)
Shortleaf Pine Pinus echinata
Unidentified pink slime mold
Clitocybe robusta mushroom (tentative) (no common name)
Mycena sp. mushroom (perhaps M. subcaerulea)
Yellow-bellied Sapsucker (evidence, holes) Sphyrapicus varius
Hop hornbeam Ostrya virginiana
Water Oak Quercus nigra
Persimmon Diospyros virginiana
Greenbriar Smilax sp.
Conifer-cone Cap mushroom Baeospora myosura
Smoked Oysterling mushroom Resupinatus applicatus
Sawtooth Oak Quercus acutissima
Banded Tussock Moth caterpillar Halysidota tessellaris
Beaked Panicgrass Panicum anceps
Shagbark Hickory Carya ovata
False Turkey Tail fungus Stereum lobatum
Turkey Tail fungus Trametes versicolor
Black Needlegrass Piptochaetium avenaceum
Nimblewill grass Muhlenbergia schreberi
Spongy Oak Apple Gall (Cynipid wasp) Amphibolips confluenta
Hawthorn Crataegus sp.
Scarlet Oak Quercus coccinea
Truncophora ohiensis syn. Perenniporia ohiensis (tent.) No common name
Round Bullet Gall Wasp Disholcaspis quercusglobulus
Beech Fagus grandifolia
Giant Bark Aphid Longistigma caryae
Red ants Family Formicidae