Leader for today’s Ramble: Roger Collins
Authors of today’s Ramble report:
Insect identifications: Don Hunter
Fungi and gall identifications: Don Hunter
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. Not all of Don’s photos from today’s ramble made it into the ramble report, so be sure to check out his Facebook album at this link.
Number of Ramblers today: 30
Today’s Emphasis: Natural environments in the Garden’s forests with special attention to the place of Beech trees in these areas.
Announcements:
Susie announced that the UGA Trial Gardens is holding its annual Public Open House on Saturday, June 8, 9:00 a.m. until 12:00 noon. All are invited. More information is at this link.
Interesting article: more DNA is not always better. “Small fern species has a genome 50 times larger than that of humans.”
“Backyard Ecology” – a helpful and interesting website for folks in the south interested in gardening for wildlife and with native plants.
Today’s Reading: Roger read “The Forest for the Trees” a poem by Rena Priest, a member of the Lhaq’temish (Lummi) Nation. She is the 2021 Washington State Poet Laureate. Her literary debut, Patriarchy Blues, was honored with a 2018 American Book Award.
I have seen a tree split in two
from the weight of its opposing branches.
It can survive, though its heart is exposed.
I have seen a country do this too.
I have heard an elder say
that we must be like the willow---
bend not to break.
I have made peace this way.
My neighbors clear-cut their trees,
leaving mine defenseless. The arborist
says they will fall in the first strong wind.
Together we stand. I see this now.
I have seen a tree grown around
a bicycle, a street sign and a chainsaw,
absorbing them like ingredients
in a great melting pot.
When we speak, whether or not
we agree, the trees will turn
the breath of our words
from carbon dioxide into air---
give us new breath
for new words,
new chances to listen,
new chances to be heard.
Sher brought two pods from the Chinese Wisteria in his and Barbara’s yard. The velvety coating of hairs on Chinese Wisteria’s fruits is one way to tell the exotic species from our native American Wisteria, which has smooth pods.
Today’s route: We headed south across the Children’s Garden toward the Callaway/Administration building, bearing left onto the Scout Connector trail which begins on the left (east) side of the building. We followed the Scout Trail down into the ravine then up, and cut cross-country to connect to the Purple Trail, which we followed to the Orange Trail by the river. We walked upriver to the ADA trail and took it to the road back to the parking lot.
Today’s observations:
Don’s Ramble actually begins as he walks through the Upper Shade Garden and the Children’s Garden on his way to the arbor, looking for anything photo-worthy and almost always coming up with some cool pics of insects and plants.
The first thing Don saw was an ant lion, adorned with pieces of fluff, plant parts, and shed skins of other insects, and other odds and ends.
Next up was a small, orange-colored orbweaver resting in a bit of her web. Despite his best efforts, Don could not identify this spider to species.
Don spotted a pair of Versute Sharpshooter leafhoppers resting on a very hairy Maximillian Sunflower leaf.
This long-legged fly is only one of the many such to be seen in the Garden during the summer.
Show-and-Tell:
Roger, today’s Ramble leader, introduced today’s topic, natural environments of the Garden, with the remarks and handouts below.
“The theme for today’s Ramble is the natural environment of the Botanical Gardens with a focus on Piedmont geology and soils, and a closer look at the place of Beech in the Garden’s forests. Much of what I have to say is based on “Natural Environments of the State Botanical Garden of Georgia” by Charles Wharton (1998). [You can access Dr. Wharton’s report at this link.]
“Forty years ago, I would take my young son down these trails, and at that time as far as I was concerned, the Botanical Garden was just a big green forest. I knew many of the trees by name, but it was a classic case of ‘You can’t see the forest for the trees.’ I didn’t see the forest of which the trees were a part. Coming to understand the forest as a matrix of natural environments created by the interaction of climate, topography, geology, and soil – helped me bring the forest into focus.
“Topography is the ‘lay of the land’ – the physical shape of the land – such as hills and valleys, ridges and ravines, cliffs and plains. The Botanical Garden encompasses three forested natural areas, each with a different topography: the Middle Oconee River flood plain, the slopes and ravines, and the ridgetops and other uplands.
“The river floodplain is a distinct natural environment subject to frequent flooding. The soil is primarily built from deposits of sand and silt left by flooding. Within the flood plain are natural features such as the beaver pond, the sandy levee built up on the banks of the river, and low, usually wet areas behind the levee called sloughs (pronounced ‘slews’). Wharton describes this natural environment as an ash-elm-birch-boxelder forest, based on the trees that dominate the floodplain: Green Ash, American Elm, Slippery Elm, River Birch, and Boxelder.
“The driest areas in the Botanical Garden are the ridgetops and associated uplands. They don’t qualify as ‘xeric’ (an ecologist’s term for sites with very dry soils such as sandhills), but are not really moist (‘mesic’) either, so we call them sub-mesic. The forest on these relatively dry sites at the Garden are usually dominated by oak and hickory trees, mainly Southern Red Oak, Scarlet Oak, Black Oak, Post Oak, Sand Hickory, Red Hickory, Mockernut Hickory, and Shortleaf Pine.
“In between the floodplain and the uplands, we have the slopes and ravines with moister soils. This natural environment is generally described as a Piedmont mesic forest. On the Ramble today, I will focus on the Beech forest – a mesic hardwood forest whose indicator species include American Beech, Northern Red Oak and Tulip Poplar trees. It is a mesic or moist environment since the slopes capture water runoff from the uplands as well as gets seepage from the bedrock slopes. Slopes and ravines receive fewer hours per day of direct sunlight so their soils stay moister longer after a rain and temperatures are more moderate.
“Today’s Ramble will follow the Scout Connector Trail to explore a ravine environment with a diverse plant community. Then we will cross a somewhat drier upper slope which includes the stone chimney remains of an old home site, probably from the late 1800s. Heading down the Purple Trail, we will come to a plant community including Chalk Maple indicating an area of underlying mafic rock called amphibolite. This is an example of how geology also helps shape the natural environments.
“Understanding the natural environments of the Georgia Piedmont requires first an understanding what is unique about Piedmont soil – in other words all this red clay under our feet. I want to share with you an epiphany that I had about Piedmont soil.
“I grew up in the Coastal Plain, and when I saw the red clay hills of the Piedmont, I assumed that this clay came from the erosion of ancient Appalachian mountains. But as I read and studied about Piedmont soil, I always came across the phrase, ‘Piedmont soil is a product of the chemical weathering of the parent bedrock.’ One day while walking a trail, I had a small epiphany about chemical weathering. Chemical weathering means that the clay soil did not come from anywhere; instead, it was created right here from the bedrock beneath our feet. In fact, it is the product of chemical weathering of the underlying crystalline bedrock – rocks such as schist, gneiss, and granite. The combination of the chemical weathering of these rocks along with a warm, moist climate created the deciduous hardwood forest around us.
“What is chemical weathering? If our climate were cold and wet, then it would be ice and snow, freezing and thawing, that would grind away at exposed bedrock. If our climate were hot and dry, it would be wind and sand that erodes the rock. This is called mechanical weathering. But our climate is warm and moist – in other words, hot and humid. Chemical weathering describes the chemical changes that happen to rocks and minerals when they are exposed to surface conditions such as rain and heat as well as the oxygen and carbon dioxide in the air. When you combine the crystalline rocks of the Piedmont with warm climate and rain and add millions of years, you get chemical weathering. The result is that our soil takes many of its qualities directly from the parent rock. Even the rust red color of the clay is from the iron in the parent rock. In the Botanical Garden, the underlying bedrock is generally biotite gneiss. This rock weathers into an acidic soil low in nutrients. But here and there in the Garden, folded into the gneiss are layers or pockets of amphibolite, a metamorphic rock derived from volcanic basalt. Amphibolite contains higher levels of nutrients such as calcium, magnesium, and phosphorous. The soil derived from this rock is less acid and contains more nutrients supporting a more diverse plant community.
“In his report on the natural environments of the Botanical Garden, Wharton describes several areas of the Garden as having ‘Beech co-dominant with oak and hickory.’ This led me to take a closer look at the Beech-dominated forests at the Botanical Garden.
“The Beech tree (Fagus grandifolia) can adapt to a range of soils and environments, but under natural conditions grows on the mesic slopes and in ravines. It does not establish well in areas with frequent standing water such as the river flood plain. Also, with its thin bark it is vulnerable to fire. If Beech does migrate into the less mesic areas of the uplands, naturally occurring forest fires would drive it back to the moister areas between the frequently flooded land below and the occasional fires above.
“I have created a map of the Beech forest to show the distribution and history of Beech trees within the Garden. To do so, I measured the diameters of 205 Beech trees. Using this raw data, I converted the diameters of the trees into estimated ages. A Beech tree takes about five years to grow one inch in diameter, so a 4-inch tree would be about 20 years old, a 10-inch tree would estimate to be 100 years old, etc. For the final step, I divided the Beech trees into age groups: 10-50 years old, 50-100 years, 100-150 years, and a group of three ‘Grandma’ Beeches that were 150 years old or more.
“Looking at the map, the trees represented by white or yellow dots show how much the Beech population has expanded over the slopes and up the ridgetops in the last 100 years. The 25 ‘magenta’ trees (100-150 years) and the 3 ‘purple’ trees (150 years or more) would show the Beech forest in about the year 1924 confined to the slopes and ravines. At this point, there seems to be something wrong or missing in this picture. Were the three 150-year-old (purple) trees the only Beech trees growing in the year 1874? (They would have been merely twiggy trees or young saplings.) Where are their parent trees? A Beech is usually 40 years old before it produces fruit, implying that these parent trees, if they existed today, would be almost 200 years old. A Beech can live 300 years or more, so it would seem that a part of the Beech forest is missing.
“The answer to these questions is probably logging. Wharton notes that in the Twentieth Century our forests, including the Botanical Garden, were subject to intensive and frequent logging especially in the 1920s and 1940s. The forest of the Botanical Garden was last logged in the early 1960s. While much of the Garden has been forested for the last 200 years, it is not an old growth forest. It suffered the ‘slash and burn’ farming of the early 1800s, followed by agricultural abandonment and second-growth reforestation, then the logging episodes of the 1900s. It is a forest in recovery.”
The first thing that caught Roger’s eye as we moved along the Scout Connector Trail was a double-trunked Beech tree.
Roger explained that this is likely a tree that was cut down several feet above the ground and responded by sprouting two new trunks from the cut stump. “Coppicing” is the term for deliberately or unintentionally producing new tree growth by cutting a tree at or near the ground. It’s an ancient practice, dating back to the Stone Age, for managing a woodland. A few years after coppicing, the new, straight growth was usually cut and used for fence poles, firewood, and shelter building. Obviously, this tree was never cut a second time and the two new trunks were left to mature.
The Scout Connector Trail led us down into a steep ravine that is reminiscent of something you might see in the mountains. The slopes are steeply pitched and a boulder-strewn creek provides cool, moist habitat for plants and animals. The drainages on the north side of the Botanical Garden are similar but are too far away for the Nature Ramblers to access in our 1.5 hour time frame. It’s a special treat to see this habitat so close to the Children’s Garden.
Three species that are common in ravine habitats at the Garden (left to right): Heartleaf or Wild Ginger; Christmas Fern glowing in the sunlight; and Ebony Spleenwort.
Roger reminded us of the impact on the Piedmont landscape of cotton farming. One reason this ravine seems so special is that it may have been spared the devastation of cotton agriculture in the 19th century. Nearly every acre of plowable land in the Georgia Piedmont was devoted to cotton or to the corn needed to fuel the men and mules who farmed it. Even so, there is no doubt that these slopes, steep as they are, were logged, at least once and maybe more often.
From the ravine, we moved uphill and walked cross-country through an oak-hickory forest to see an old homesite, probably inhabited by members of the White family in the mid-18th century. John R. White bought this property in the 1850s, and eventually became a well-to-do factory owner and banker, owning about 2,000 acres in the vicinity of what is now the Botanical Garden and Whitehall Forest. All that remains of the house are the fireplace and chimney (below). Given the steepness of this slope, the house was probably built on a foundation of stone piers. A number of large boulders are scattered nearby, perhaps the remains of the stone piers. Nearby were the remains of an old well or cistern, used to supply drinking water.
We descended the slope and found our way onto the Purple Trail, and continued downhill toward the river.
Two mature Northern Red Oaks were recently blown down along the Purple Trail. Ramblers have noticed over the past decade or so that the majority of wind-downed trees in the Garden’s forests are Northern Reds. Northern Red Oak is essentially a northern tree with populations as far north as Nova Scotia and Minnesota. The southernmost populations of Northern Red Oak in Georgia are near Macon, only 100 miles south of Athens. It seems likely that climate change – hotter temperatures, longer droughts, more intense storms – will eventually move the southern limit of this species’ range up into the mountains. Another factor at work is the shallowness of our topsoils (legacy of 150+ years of cotton agriculture) which prevents these typically deep-rooted trees from finding a firm footing. According to a U.S. Forest Service publication, “The most important factors determining site quality for northern red oak are depth and texture of the A soil horizon, aspect, and slope position and shape. The best sites are found on lower, concave slopes with a northerly or easterly aspect, on soils with a thick A horizon, and a loam to silt loam texture.” Sadly, the A horizon (top soil) has long since been eroded from these slopes, and hard clay soil is resistant to penetration by this species’ roots.
Sourwood is a common component of the subcanopy in Oak-Hickory forests at the Garden; it prefers acidic soils. Its trunk is typically sinuously curved, stretching and twisting as it grows toward a light gap in the dense canopy of oak and hickory leaves.
A coppiced Beech with three trunks that arose from a stump.
The Purple Trail more or less follows the ridgeline down to the river. The vegetation on the lower half of the trail – a subcanopy of the calcium-loving species Chalk Maple (photo left, below) and Hop Hornbeam – suggests that the ridge consists of an erosion-resistant rock called amphibolite (photo right, below). Amphibolite rocks are high in the basic elements calcium, magnesium, and iron and and are typically speckled black and white inside with a rind of rusted iron. Because of their high iron content, amphibolite rocks feel heavier than they appear.
When we reached the Orange Trail, we turned upriver and followed the trail along the base of the slope, with the river levee to our left. We continued to see the calcium-loving species mentioned above, plus Honewort (below), a member of the Parsley family. Either the amphibolite bedrock continues down to the river or soils derived from amphibolite have washed off the ridge and accumulated in the floodplain.
Scenes from the Orange Trail along the Middle Oconee River….
Trooping Crumble Cap mushrooms growing on a log by the trail. Photo by Bill Sheehan.
Southeastern Wild-rye is in flower along the Orange Trail and in the right-of-way, its yellow anthers on full display and ready to release pollen. There is no sign here of the pollen-receptive styles which will develop after the anthers wither to prevent self-pollination.
The Rye from which bread is made is in a different genus, Secale, native to the Old World.
As the Ramble wound down, many of us lingered at the River Cane patch on the river at the end of the paved ADA trail. There were several weedy-looking mystery plants requiring intervention with the Seek app. The plant pictured above was the biggest surprise. This is Epazote, aka Mexican Tea, an herb in the Goosefoot Family (Chenopodiaceae), a family that also includes Quinoa, Beets, Spinach, and Chard. Epazote (pronounced eh-pah-ZOH-teh) is used in cooking and traditional medicine throughout much of Mexico and Central and South America. Because of its long and widespread use by humans, its native range is unclear but may include southern Texas and adjacent areas. It is currently found throughout much of North America, mostly as a non-native weed.
Clustered Dock, a European invasive species, was another weedy species new to us. What looks from a distance to be small, white fruits are actually swellings on the midveins of the petals. These swellings, called tubercles, are characteristic of most species in the Dock genus Rumex.
This drawing from the Flora of North America shows a swollen tubercle on the midvein of a petal.
Meanwhile, Bill was gall-hunting and came across a gall created by a Carbonifera Goldenrod Gall Midge, a co-star in a three-way relationship with a fungus and a plant. A female midge of this species carries fungal spores in a pouch in her abdomen; when she inserts an egg into the leaf of a goldenrod she also deposits some fungal spores. As the fungus develops, it envelops the egg and the larva that hatches from it (see the photo below). Without the fungus, the midge larva will not mature. The fungus provides food for the growing larva and protection too, especially from parasitic wasps who would lay their eggs on the larva except for the tough coating of the fungus. The fungal spores will not develop unless deposited on a goldenrod by the midge. The goldenrod (in this case, Tall Goldenrod) is apparently unaffected by all this since the gall is made totally out of fungus with no plant tissue involved. So, all parties are happy. Bill’s photos above show goldenrod leaves with the fungus, a closeup of the fungal case, and the black interior of the fungal case. For more information on this fascinating relationship, check out this website.
Bill made a cross-section of the gall in his lab, revealing the glossy black-and-tan body of the midge larva encased by the gall.
SUMMARY OF OBSERVED AND DISCUSSED SPECIES
Green Lacewing (antlion/larva) Chrysopa sp.
Orbweaver spider (No species ID) Family Araneidae
Versute Sharpshooter leafhopper Graphocephala versuta
Long-legged fly Family Dolichopodidae
Maximillian Sunflower Helianthus maximilliani
Green Ash Fraxinus pennsylvanica
American Elm Ulmus americanus
Slippery Elm Ulmus rubra
River Birch Betula nigra
Box Elder Acer negundo
Southern Red Oak Quercus falcata
Post Oak Quercus stellata
White Oak Quercus alba
Sand Hickory Carya pallida
Red Hickory Carya ovalis
Mockernut Hickory Carya tomentosa
Shortleaf Pine Pinus echinata
American Beech Fagus grandifolia
Heartleaf (Wild) Ginger Hexastylis arifolia
Christmas Fern Polystichum acrostichoides
Kunth’s Maiden Fern Thelypteris kunthii
Ebony Spleenwort Asplenium platyneuron
Northern Red Oak Quercus rubra
Sourwood Oxydendrum arboreum
Chalk Maple Acer leucoderme
Trooping Crumble Cap Coprinellus disseminatus
Southeastern Wild Rye Elymus glabriflorus
Honewort Cryptotaenia canadensis
Spotted Cucumber Beetle Diabrotica undecimpunctata howardi
River Cane Arundinaria gigantea
Mexican Tea (Epazote) Dysphania ambrosiodes
Clustered Dock Rumex conglomeratus
Tall Goldenrod Solidago altissima