Leader for today’s Ramble: Roger Nielsen
Authors of today’s Ramble report: Linda Chafin, Don Hunter
Insect and gall identifications: Don Hunter
The photos that appear in this report 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.
Nature Ramble rainy day policy: We show up at 9:00am, rain or shine. If it’s raining, we will meet and socialize in the conservatory (bring your own coffee); if there is a break in the rain, we’ll go outside and do a little rambling.
Number of Ramblers today: 34
Today’s Emphasis: “Fightin’ for the light!” – how plants compete for light.
Announcements and other interesting things:
Next week’s Ramble, on July 4th, will be held at Sandy Creek Nature Center (NOT Sandy Creek Park, NOT the Bot Garden), at 205 Old Commerce Rd, Athens. Ramblers will meet in the Nature Center parking lot by the Visitor Center/Education Building at 9:00 a.m. Halley is inviting everyone to her house afterward for a potluck (she will provide drinks only). Her address is 405 Ponderosa Drive, in the Cedar Creek subdivision. Text her if you have questions: 706-318-0854.
Coral reefs are in the news: https://www.nytimes.com/2024/06/24/science/coral-reef-trafficking-aquariums.html
Today is the first day of Summer, the summer solstice. Roger provided this info on the solstice from “This Week’s Sky at a Glance” in Sky and Telescope Magazine and also from USA Today.
“Happy solstice! At 4:45 p.m. EDT, the Sun reaches its farthest north position in Earth’s sky and begins its six-month return southward. Astronomical summer begins in the Northern Hemisphere, winter in the Southern Hemisphere. For us northerners, this is the year’s longest daylength (duration of exposure to insolation) and shortest night.
This is the earliest solstice since June 20, 1796, when George Washington was president and there were only 16 states in the Union. It’s also the day when, here in the north temperate latitudes, the midday Sun passes the closest it ever can to being straight overhead, and thus when your shadow becomes the shortest it can ever be at your location. This happens at your local apparent (solar) noon, which is probably rather far removed from noon in your civil (clock) time. And if you have a good west-northwest horizon (in mid-northern latitudes), mark carefully where the Sun sets. In a few days you should be able to detect that the Sun is once again starting to set just a little south (left) of that point.
Many people around the world celebrate the summer solstice with music and festivities. In England, hundreds of people travel to the ancient site Stonehenge for the first day of summer. Solstice observations there have been going on annually for thousands of years. The Stonehenge rock formation perfectly aligns with the sun's movement on both the summer and winter solstices. Although its origins and reasons for its creation are not understood, Stonehenge has become one of the most popular places to observe the solstice. The Mayans and Aztecs also used the summer and winter solstices as markers to build structures that precisely line up with shadows created by the sun.”
Reading: Roger read from “The Harvest of a Quiet Eye,” by Odell Shepard, pp. 133-134, (1927).
"A little stream, six or seven feet in width and not more than ten inches deep in most places, flows down before me through a glade of pines, coming out of a clearing just visible through the dark stems above and going down into another. There is deep shadow, of the peculiarly lustrous and richly colored kind that only pines can throw, upon most of its course, and this shadow is darkest on the glossy broad pool some thirty feet up the stream, but elsewhere the sunlight dazzles in patches upon white water. The banks on either side are purple with pine needles. A rod or two up the water there is a foot-bridge of two mouldering planks, and beyond that a fence of sagging wire to separate the glade from the clearing.
In this rough outline there is nothing much to excite attention. Nearly all the values lie in minute details, as they must in landscapes drawn to so small a scale, and for this reason, precisely, the forest brook provides the best possible education for the eye. There is always more to be seen in it than any one has yet seen. A [person] may gaze at a small patch of stream-surface until [they have] exhausted every trait of motion, shape, and hue; then [one] looks again, and finds that [one] has just begun to spell out its primer. Not that a brook ever tries to hide anything, for there is nothing more frank and generous in self-revelation; but its carvings are so many and its nuances of color so fine, its endless dance is so full of what looks like pure whim and caprice, that it daunts and finally eludes the most patient skill of the eye. One who has learned to see a brook can see anything."
Show and Tell: Roger brought a section of an Eastern Hemlock limb from his yard. The growth rings on one side of the limb were much wider than those on the other side. Roger told us that when the top – the leader – of the Hemlock’s trunk was broken off in a storm, one of the nearby branches started growing vertically and assumed the leader position.
There are two different plant responses to damage and stress going on here. The first is a phenomenon in plants called “apical dominance” – the tips of plant stems release a hormone called auxin that suppresses or limits the growth of branches down below. When the tip is broken or damaged, auxin production is reduced and lower branches begin to expand from buds lower down on the stem (anyone who has ever pruned a shrub to encourage “bushiness” has seen this). The second stress response is the laying down of what is called “compression wood.” Once free of apical dominance, the limb from Roger’s tree began to grow laterally (sideways) then turned upward to assume the position of the leader. As the limb grew both upward and in girth, it laid down “compression wood” – wider rings on the lower side of the limb that “pushed” the limb up and also provided more support. Compression wood rings are not only wider but also contain more of the substance called lignin that give plant cell walls their strength; in Roger’s tree, it both strengthened and straightened the limb on its way to being the new leader.
Today’s Route: We walked between the Porcelain and Decorative Arts Museum and the Visitor Center, skirted the Heritage Garden, and walked downhill to the boardwalk. We then followed the Woodland Walk Trail to the Orange Trail Spur, and took the spur down to the Orange Trail, where we crossed the creek and headed downstream to the High Water Bridge. We followed the High Water Trail, then turned uphill onto the Purple Trail, returned to the visitor center by way of the Flower and Heritage Gardens.
Common Eastern Bumblebee nectaring on the disk flowers of a Purple Coneflower. The disk flowers, with their yellow anthers, are tucked in between the stiff, orange scales that characterize this genus. These scales are sometimes called chaff or pales. Bumblebees’ long tongues can reach down between the scales to reach the tiny, nectar- and pollen-producing disk flowers. Coneflowers must be cross-pollinated in order to set seed.
As Roger predicted, we began to see examples everywhere of plants “fighting for the light.” Without adequate light, plants switch their growth into what is called “shade avoidance response,” and re-allocate energy into growing taller or longer to reach the light. Unfortunately, this comes at a cost: root growth is stunted and plants bloom sooner than normal, responding to the evolutionary imperative to pass their genes to the next generation before it’s too late.
Thread-leaf Bluestar is a full-sun species growing away from overhanding shrubs and toward the higher light of the sidewalk.
Sumac shrubs planted on the edge of the China Section are leaning to the sun that falls on the sidewalks. Sumac is a native shrub of full-sun habitats that typically grows with an erect stem.
Painted Buckeye is a native shrub that is adapted to live in the low light of the forest understory. In such forests, as little as 5% of the solar radiation above the forest canopy actually reaches the forest floor. Plants living in such deep shade are dependent on “sun flecks,” bits of sunlight that reach the ground as the wind moves leaves and branches around or as the sun travels across the sky during the course of the day. Each sun fleck may last only seconds or minutes but they account for more than 80% of the light that reaches plants on the forest floor. Buckeye’s divided leaves allow light to filter through to its lower leaves.
The forest understory includes trees that are adapted to low light and never reach the canopy, such as Flowering Dogwood, Hop Hornbeam, and Chalk Maple. But many of the woody plants seen in the understory are actually shade-tolerant seedlings and saplings of canopy species such as Beech and Red Maple that can persist for decades in the low light, waiting for a gap in the canopy. If a large tree dies or is blown down in a storm, these saplings can grow quickly to establish their place in the canopy before the gap is filled. As much as we mourn when we see a large old tree blown down, its death may provide other species an opportunity to diversify the forest canopy.
Ash trees are shade-tolerant as seedlings and can hang on for years receiving as little as 3% of full sunlight. When a gap opens up, they can grow rapidly to reach the canopy.
Tall Pawpaw is a native, shade-tolerant understory species that forms thickets by the spread of underground stems. It rarely reaches more than 30 feet in height.
Sourwood is a shade-tolerant tree yet its shape is strongly determined by its search for more light. Their trunks and upper branches often grow in sinuous curves as they follow light gaps that open up in the forest. At the Garden we often see them reaching toward roads and trails, as in this photo.
Given the chance, Water Oak also grows toward the light, but its seedlings can persist in the ground layer for years, growing as little as 2 inches in height per year. A cross-section of the trunk would show that the innermost growth rings are so narrow they can’t be counted. This Water Oak, left, has several trunks, each going their own way in search of light, a situation that will probably result in the tree splitting apart in ice or snow storms.
Even on a tree walk, it’s a good idea to look down every now and then!
Garter Snake (above) and Bluehead Chub in the Orange Trail creek (below).
Amelia found several Scarlet Elf Cup fungi on a rotting branch.
Emerging from the woods into the Flower Garden, then moving through the Heritage Garden, ramblers made several noteworthy observations.
Walking Stick insects typically inhabit shade forests and feed exclusively on vegetation.
This coneflower head is infected with “Aster yellows,” a disease spread by an insect called Aster Leafhopper. The disease organism is a phytoplasma, a bacterium that lacks a cell wall and has a tiny genome. It is a deadly infection, necessitating the removal of all infected plants. More info on Aster Yellows is here and here.
Sumac Gall on the leaves of Smooth Sumac, planted at the bottom of the Flower Garden. The gall is the result of egg-laying by aphids.
In a Nature Ramble report from August 19, 2021, Dale illuminated the lives of these tiny aphids: “At the bottom of the Flower Garden some of us discovered numerous pouch-like swellings on the Sumac leaves and midvein. These are the work of an aphid called the Sumac Gall Aphid. In the spring, as the Sumac is producing leaves, it is visited by an aphid that lays a single egg, usually on the mid-vein. The plant reacts by enveloping the egg with a growth of tissue that begins as a small, spherical swelling. The egg hatches and the aphid nymph inside the gall begins feeding by sucking plant juices. When the nymph becomes sexually mature it starts to produce more aphids parthenogenetically; i.e., without benefit of a male, inside the gall. Those aphids, in turn, produce more aphids and the number within a single gall grows exponentially. Ultimately the aphids leave the gall and migrate to mosses that may be growing nearby. There they over-winter and, in the spring, both female and male aphids are produced; they mate and the females fly off to find more sumac, completing the life cycle. We opened several of the thin-walled galls and found them filled with white fuzz. It didn’t dawn on me what this was until much later: the cast off exoskeletons of hundreds if not thousands of aphids. Each aphid molts five times before reaching reproductive age. Given the exponential rate of increase of the aphids and then multiply by five and you get a gall filled with white fluff. Visit this website for a lot of excellent photographs of the galls and the aphids.”
Black-eyed Susan (left) and Bee-blossom (right) are two of many beautiful natives thriving in the Flower Garden.
SUMMARY OF OBSERVED, DISCUSSED, AND HEARD SPECIES:
Versute Sharpshooter Graphocephala versuta
Ligated Furrow Bee Halictus ligatus
Scentless Plant Bug Harmostes sp.
Eastern Hemlock Tsuga canadensis
Purple Coneflower Echinacea purpurea
Common Eastern Bumble Bee Bombus impatiens
Sumac Rhus sp.
Wood Thrush (song) Hylocichla mustelina
Jack-in-the-Pulpit Arisaema triphyllum
Painted Buckeye Aesculus sylvatica
Thread-leaf Bluestar Amsonia hubrichtii
Pitcher plants Sarracenia spp.
American White Water Lily Nymphaea odorata
Wax Myrtle Myrica cerifera
Flowering Dogwood Cornus floridus
Hop Hornbeam Ostrya virginiana
Chalk Maple Acer leucoderme
Beech Fagus grandifolia
Red Maple Acer rubrum
Green Ash Fraxinus pennsylvanica
Tall Pawpaw Asimina triloba
Sourwood Oxydendrum arboreum
Water Oak Quercus nigra
Common Garter Snake Thamnophis sirtalis
Bluehead Chub Nocomis leptocephalus
Scarlet Elf Cup fungus Sarcoscypha coccinea
Stick insect/Walking Stick Order Phasmatodea
Asters Yellow (phytoplasma) Candidatus Phytoplasma asteris
Smooth Sumac Rhus glabra
Sumac gall aphid Melaphis rhois
Black-eyed Susan Rudbeckia hirta
Gaura/Bee-blossom Gaura sp.