Leader for today's Ramble: Dale
Number of Ramblers today: 32
Today's emphasis: Trees on the White Trail, old access road and Green Trail
Note: Don was unable to attend today's Ramble, so there will be no Facebook album to document what we observed. Instead, I've used his photographs from past Rambles and photos sent to me by fellow ramblers. If there is no attribution for a photo, it was taken by Don Hunter.
Number of Ramblers today: 32
Today's emphasis: Trees on the White Trail, old access road and Green Trail
Note: Don was unable to attend today's Ramble, so there will be no Facebook album to document what we observed. Instead, I've used his photographs from past Rambles and photos sent to me by fellow ramblers. If there is no attribution for a photo, it was taken by Don Hunter.
Reading: Bob Ambrose read an Emily Dickinson poem suggested by Sandy Shaul:
Today's Route:
Two butterflies went out at Noon —
And waltzed upon a Farm —
Then stepped straight through the Firmament
And rested, on a Beam —
And waltzed upon a Farm —
Then stepped straight through the Firmament
And rested, on a Beam —
And then — together bore away
Upon a shining Sea —
Though never yet, in any Port —
Their coming, mentioned — be —
If spoken by the distant Bird —
If met in Ether Sea
By Frigate, or by Merchantman —
No notice — was — to me —
1. It is time to order your Nature Ramblers t-shirt! They need to be ordered before Nov. 1 (Last day to order is Oct. 31.) Here is link for ordering.
All profits from the t- shirts will go to the Botanical Garden to support the new Butterfly Trail.
2. Please join the Friends of the Georgia Museum of Natural History. As UGA charts the future Museum’s future, your membership in the Friends is vital to demonstrate public support for the Museum and natural history. You can join online and pay through PayPal or with a credit card.
Once you join or if you are already a member, you are invited to an outdoor members only event on Sunday, October 24 from 4-6, On The Hill. RSVP at events@gmnhfriends.org.
3. Dan Williams will lead a Tree Ramble at Sandy Creek Nature Center on Wednesday, November 3rd at 9 AM. We will meet at the front of the Education and Visitors Center. Bring a mask and your enthusiasm!Today's Route:
Sidewalk
from the Pergola to mulched path through the Dunson Garden. Across paved
road on White Trail spur, across ROW to point inside the woods where
White, Green and Blue trails join. Then follow White Trail to access
road, take access road toward the river to the Green Trail crossing; the
Green Trail back to junction with White Trail.
OBSERVATIONS:
American Beech
The first thing that strikes you about a Beech tree is its smooth, gray bark. (And, often, the declarations of love inscribed in that bark by adolescent boys with pocket knives.) There are other features that are unique to Beeches: Their elongate, pointed buds at the ends of each branch or at the base of most of the leaves. The leaves have wavy edges, each "wave" bearing a tiny prickle.
A good mnemonic for remembering the leaf edge: "Where do you find waves? At the beach (Beech)."
Etymology
Avis told us that the word Beech has the same root as the word Book, indicating that people have been writing on Beech trees since the dawn of time, or something like that. Online Etymology Dictionary confirms it: "German Buch 'book' and Buche 'beech'; see beech), the notion being of beechwood tablets on which runes were inscribed; but it may be from the tree itself (people still carve initials in them)."
Smooth bark
Trees have two sets of embryonic tissues called cambiums; the vascular cambium and the cork cambium. These are like stem cells in animals. When they divide either both daughter cells remain cambium cells or one remains a cambium cell but the other differentiates into a different specialized cell that is incapable of further cell division.
The vascular cambium cells form a sheath that surrounds the entire tree, trunk, branches and twigs. It causes the tree to increase in diameter. The vascular cambium produces the cells that become the woody part of the tree, the xylem. Xylem tubes conduct water from the roots to the rest of the tree, branches, twigs, flowers, fruits and leaves. Each year the activity of the vascular cambium adds approximately 1/16 to 1/8 inch to the diameter of the trunk.
Outside the layer of vascular cambium is a layer of different embryonic tissue, the cork cambium. This layer of cells produces the bark. The cells it produces on the outer surface pile up and die, becoming a layer of corky cells of variable thickness. (Wine corks are made from the bark of the Cork Oak.)
If the cork cambium can keep pace with the vascular cambium the resulting bark is smooth and thin, like in the Beech. If it can't keep up with the vascular cambium the bark is stretched and finally breaks apart. The bark pattern that is formed depends on the difference in reproductive rate of the two cambiums and the strength of connection between the dead cork cells in the bark, giving each tree species a different bark pattern.
Marcescence
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| American Beech trees with smooth, gray bark | . |
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| American Beech leaves with "wavy" edges. |
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| American Beech terminal bud; shaped like a pointed cigar. |
American Beech
The first thing that strikes you about a Beech tree is its smooth, gray bark. (And, often, the declarations of love inscribed in that bark by adolescent boys with pocket knives.) There are other features that are unique to Beeches: Their elongate, pointed buds at the ends of each branch or at the base of most of the leaves. The leaves have wavy edges, each "wave" bearing a tiny prickle.
A good mnemonic for remembering the leaf edge: "Where do you find waves? At the beach (Beech)."
Etymology
Avis told us that the word Beech has the same root as the word Book, indicating that people have been writing on Beech trees since the dawn of time, or something like that. Online Etymology Dictionary confirms it: "German Buch 'book' and Buche 'beech'; see beech), the notion being of beechwood tablets on which runes were inscribed; but it may be from the tree itself (people still carve initials in them)."
Smooth bark
Trees have two sets of embryonic tissues called cambiums; the vascular cambium and the cork cambium. These are like stem cells in animals. When they divide either both daughter cells remain cambium cells or one remains a cambium cell but the other differentiates into a different specialized cell that is incapable of further cell division.
The vascular cambium cells form a sheath that surrounds the entire tree, trunk, branches and twigs. It causes the tree to increase in diameter. The vascular cambium produces the cells that become the woody part of the tree, the xylem. Xylem tubes conduct water from the roots to the rest of the tree, branches, twigs, flowers, fruits and leaves. Each year the activity of the vascular cambium adds approximately 1/16 to 1/8 inch to the diameter of the trunk.
Outside the layer of vascular cambium is a layer of different embryonic tissue, the cork cambium. This layer of cells produces the bark. The cells it produces on the outer surface pile up and die, becoming a layer of corky cells of variable thickness. (Wine corks are made from the bark of the Cork Oak.)
If the cork cambium can keep pace with the vascular cambium the resulting bark is smooth and thin, like in the Beech. If it can't keep up with the vascular cambium the bark is stretched and finally breaks apart. The bark pattern that is formed depends on the difference in reproductive rate of the two cambiums and the strength of connection between the dead cork cells in the bark, giving each tree species a different bark pattern.
Marcescence
Some young trees and lower limbs of older trees hang onto their dead leaves throughout the winter, a phenomenon called marcescence. Cells in the outer abscission layer do not completely break down (see image below from Linda's winter tree class handout that shows the abscission zone).
Trees in our area that practice marcescence: American Beech, Oaks, Hop Hornbeam, Musclewood and Chalk Maple.
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| Abscission zone at base of leaf petiole. If the separation layer doesn't break the leaf will hang on the tree until spring. (Illustration compliments of Linda Chafin.) |
This phenomenon is something of a puzzle. Why should a plant retain dead leaves over the winter? There are around a dozen hypotheses, none of which are clearly correct, or clearly wrong. This website has a summary of them.
Jim told us that the retained leaves of Beech become paler and paler during winter, appearing to him as "ghosts of the forest."
For an explanation of why and how trees drop their leaves check out this Nature Rambling post.
Mockernut hickory
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| Mockernut Hickory bark (photo by Susan Brown) |
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| Left, Mockernut Hickory fruit; note thick husk and large nut. Right, Red/Pignut Hickory with smaller nut and thin husk. |
Mockernut hickory has very distinctive braided bark. The nut is surrounded by a very thick husk. Linda prepared a guide to identification of our local Hickories. It can be downloaded from this location: Hickories in the Georgia Piedmont.
Gary Crider told us about boiling Mockernut nutmeats and finding them tasty as opposed to
the literature which says they are bitter.
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| American Toad (not the one we saw today, but it has similar coloration). The swellings just behind the eyes are parotoid glands that contain a cocktail of toxic substances. |
American Toad
Someone discovered an American Toad near the base of the Mockernut Hickory. This was no mean feat. The toad had a reddish-brown coloration that perfectly matched the soil as well as the leaf litter. If it hadn't moved we would have missed it.
Toads are famous for being warty, but they don't cause warts if handled. There is a different reason to avoid rough handling. Behind the eyes, on the top of the head are a pair of swollen lumps, the parotoid glands. (Not to be confused with the parotid gland, which is a type of salivary gland in the mouth.) Parotoid glands secrete a very toxic, milky white fluid when the toad is roughly handled. (You may have heard of the death of dogs in Florida and Australia after attempting to eat a large species of toad, the Cane Toad, Rhinella marina (formerly Bufo marinus). Australian snakes and mammals have also died from attempts to eat Cane Toads.)
If you've ever picked up a toad you probably got your hands wet when it emptied its bladder. This is probably worse for the toad than for you. Toads are in danger of dehydration and the loss of all that bladder water could endanger it. Gentle handling will not cause the release of the toxins from the parotoid gland. They have to come in contact with your mouth membranes to be absorbed. After handling a toad, wash your hand, just in case.
Linda noticed the toad's throat moving up and down and wanted to know if it was breathing. The short answer is yes, but the long answer is more interesting. When humans breath two groups of muscles are involved: the diaphragm and the rib muscles. When the rib muscles contract they pull the ribs upward. When the diaphragm contracts it drops downward. Both movements increase the volume of the thoracic cavity, lowering the pressure on the lungs. This lowered pressure draws air into the lungs. When the diaphragm and rib muscles relax they return to their resting position, which squeezes the lungs, expelling the air. You probably remember this from grade school. Frogs and toads can't breathe this way - they don't have ribs and they don't have a diaphragm. So how do they breathe?
Breathing begins with getting oxygen into the blood. In humans the lungs are where this happens. In frogs and toads there are three places where oxygen enters the circulatory system: lungs, skin, and the the lining of the mouth. All these locations bring numerous fine blood vessels (capillaries) into close contact with a moist surface exposed to air. It is there that oxygen diffuses into the red blood cells of the circulatory system.
Toads are famous for being warty, but they don't cause warts if handled. There is a different reason to avoid rough handling. Behind the eyes, on the top of the head are a pair of swollen lumps, the parotoid glands. (Not to be confused with the parotid gland, which is a type of salivary gland in the mouth.) Parotoid glands secrete a very toxic, milky white fluid when the toad is roughly handled. (You may have heard of the death of dogs in Florida and Australia after attempting to eat a large species of toad, the Cane Toad, Rhinella marina (formerly Bufo marinus). Australian snakes and mammals have also died from attempts to eat Cane Toads.)
If you've ever picked up a toad you probably got your hands wet when it emptied its bladder. This is probably worse for the toad than for you. Toads are in danger of dehydration and the loss of all that bladder water could endanger it. Gentle handling will not cause the release of the toxins from the parotoid gland. They have to come in contact with your mouth membranes to be absorbed. After handling a toad, wash your hand, just in case.
Linda noticed the toad's throat moving up and down and wanted to know if it was breathing. The short answer is yes, but the long answer is more interesting. When humans breath two groups of muscles are involved: the diaphragm and the rib muscles. When the rib muscles contract they pull the ribs upward. When the diaphragm contracts it drops downward. Both movements increase the volume of the thoracic cavity, lowering the pressure on the lungs. This lowered pressure draws air into the lungs. When the diaphragm and rib muscles relax they return to their resting position, which squeezes the lungs, expelling the air. You probably remember this from grade school. Frogs and toads can't breathe this way - they don't have ribs and they don't have a diaphragm. So how do they breathe?
Breathing begins with getting oxygen into the blood. In humans the lungs are where this happens. In frogs and toads there are three places where oxygen enters the circulatory system: lungs, skin, and the the lining of the mouth. All these locations bring numerous fine blood vessels (capillaries) into close contact with a moist surface exposed to air. It is there that oxygen diffuses into the red blood cells of the circulatory system.
Of the three sites in frogs and toads, oxygen absorption at the skin continues constantly.
The other two locations, mouth and lungs involve some other structures: the nostrils and the glottis.The glottis is a valve in the esophagus that opens to allow air to pass into and out of the lungs. The glottis sits atop the larynx in frogs and toads as it does in humans. (At one time or another we've all had food go down the wrong way. That was a failure of the epiglottis, a flap that keeps food from getting into the lungs -- when it works properly.) In frogs and toads the glottis just opens or closes, there is no epiglottis.
Frogs and toads can open and close their nostrils. You and I can't.
We're ready to find out how frogs and toads breathe.
Mouth respiration, which Linda observed, occurs when the nostrils are open, the glottis is closed and the floor of the mouth is pulled down by muscles, enlarging the mouth cavity and lowering the air pressure in the mouth. This draws air in through the open nostrils and mouth capillaries pick up the oxygen in the fresh air that enters the mouth. This mouth breathing is what Linda noticed -- the toad's "throat" was fluttering rapidly up and down.
How does air get into the lungs? First, nostrils open, glottis closed, mouth floor drops further than when just mouth breathing. Then the nostrils close and the glottis opens as the floor of the mouth rises. The air can't get out through the closed nostrils so it gets pushed into the lungs through the open glottis. Reversing this process moves air out of the lungs into the mouth. Then the glottis is closed and the nostrils open. When the floor of the mouth moves up it pushes the stale air out the nostrils. What moves the air out of the lungs? The lungs are elastic bags with a few muscles. When the lungs are filled and the glottis opens the lungs relax, expelling some of the air into the mouth cavity. Like a partially inflated balloon expells air when it's opened.
White Oaks or Red Oaks
The Oaks in our area fall into two groups: the Red Oak group and the White Oak group. Here are some of the differences:
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| Comparison of White Oak and Red Oak leaves. Left: White Oak leaf; note rounded lobes. Right: Red Oak leaf; note pointed, bristle=tipped lobes. |
White Oak group:
Leaf lobes: rounded, no bristle tip
Acorns mature in their first year
Acorns germinate in fall of first year
Acorns have lower tannin content
Red Oak group:
Leaf lobes: pointed, with a bristle tip
Acorns mature in their second year on tree
Acorns germinate in spring of following year
Acorns have higher tannin content
Tannins are bitter tasting compounds. If you've ever tasted a persimmon before it's ripe you know how it "puckers" your mouth. That was tannin that did that. When squirrels are preparing for winter they gather acorns and bury them for later retrieval and consumption. But squirrels frequently eat White Oak acorns, instead of being buried. When they are buried, the squirrel will often bite off the bottom end of the acorn, where the plant embryo is located, thus preventing the acorn from germinating. Red oak acorns are buried intact.
Jim told us about another difference between the Red and White Oak groups. The water conducting cells of trees, the xylem, are replaced every year. The older cells are dead and, in the White Oak group, are filled with balloon-like structures called tyloses. Red Oak xylem tubes remain unfilled. If you take a piece of Red Oak wood and put your lips to one end, you can blow cigarette smoke out the other end. This stunt fails with White Oak wood.
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| White Oak leaf; note the rounded lobe tips and lack of bristles | . |
Linda told us about the outbreak of Black-dotted Brown Moth on White Oaks in Athens 10 years ago. The affected trees lost their characteristic pale gray bark because birds were flicking the the loose plates off the trunks to get at the millions of caterpillars that were hiding under the bark. Fellow Ramblers talked about how people coated the trunks of oak trees in their yards with Crisco shortening to deter the caterpillars. Also download this pdf file about the Black Dotted Brown Moth.
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| Comparison of Red oak group leaves From Left to Right: Southern Red Oak (sun leaf) Southern Red Oak (shade leaf) Scarlet Oak Northern Red Oak |
Northern Red Oak is one of the commonest oaks in the garden. The trunk has "ski trails." The ridges of bark are smooth and reflect light, giving the impression of ski tracks going up and down the trunk. The leaves are broad with shallow sinuses and each lobe end in a sharp point.
Southern Red Oak is found in dry, upland sites. The leaf undersurface is white, due to the density of white hairs that reflect the light and slows moisture loss. Leaves are thick and hang perpendicular to ground and parallel to sun. They are also more variable in shape, ranging from elongate with slightly curved main vein, like the blade of a scythe, to a bell shaped (rounded) leaf base and a prominent "clapper." The bell shape of the shade leaves provides another mnemonic: bell-shaped leaf base = Southern Bell(e) = Southern Red Oak. The trunk lacks the "ski trails" of the Northern Red Oak.
White ash
Linda pulled out her pocket knife and sliced off a think sliver of bark to show us the inner bark color orangey-tan. White ash grows in more upland sites while Green Ash grows in moister situations, like flood plains and stream banks. They can told apart by details like the location of the lateral bud relative to the leaf scar or the shape of the samara with its seed.
Sun leaf vs shade leaf
Leaves, even on the same tree, vary a lot. The position of the leaf on the tree makes a difference in its structure. Leaves low on the tree or on the north side get less sunlight than leaves at the top or on the south side. As a rule of thumb: the more light received, the smaller, thicker and darker green a leaf is. Less light: leaves are larger, thinner and paler green. These differences are adaptive. Leaves exposed to higher winds need to be smaller to reduce water loss. At the same time, on the top of a tree, they can pack in extra layers of green, photosynthetic cells to capture more of the intense light. Leaves in the shade are not exposed to high winds and can have a larger surface area to capture the attenuated sunlight.
Burls were seen on several trees (the photo is from a previous ramble). They are woody, rounded masses on the trunks and roots of trees caused by a pathogen – bacteria, fungi, or virus that has invaded the live tissue beneath the bark. The pathogen releases chemicals that stimulate the production of tumor-like tissue. This tissue isolates and contains the invader so that the damage is limited to the burl. Burls are usually not fatal and will continue to grow with the tree, laying down annual rings like the rest of the tree. Burls are much sought after by wood turners, who turn the crazy growth pattern of burl cells into works of art.
Scarlet oak
Sun leaf vs shade leaf
Leaves, even on the same tree, vary a lot. The position of the leaf on the tree makes a difference in its structure. Leaves low on the tree or on the north side get less sunlight than leaves at the top or on the south side. As a rule of thumb: the more light received, the smaller, thicker and darker green a leaf is. Less light: leaves are larger, thinner and paler green. These differences are adaptive. Leaves exposed to higher winds need to be smaller to reduce water loss. At the same time, on the top of a tree, they can pack in extra layers of green, photosynthetic cells to capture more of the intense light. Leaves in the shade are not exposed to high winds and can have a larger surface area to capture the attenuated sunlight.
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| Burls distort the trunk of a tree. |
Burls were seen on several trees (the photo is from a previous ramble). They are woody, rounded masses on the trunks and roots of trees caused by a pathogen – bacteria, fungi, or virus that has invaded the live tissue beneath the bark. The pathogen releases chemicals that stimulate the production of tumor-like tissue. This tissue isolates and contains the invader so that the damage is limited to the burl. Burls are usually not fatal and will continue to grow with the tree, laying down annual rings like the rest of the tree. Burls are much sought after by wood turners, who turn the crazy growth pattern of burl cells into works of art.
Scarlet oak
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| Scarlet Oak leaf Note the very deep sinuses (the space between the leaf lobes.) My finger and thumb are inserted in the first pair of sinuses. |
Scarlet Oak is a member of the Red Oak group. It's leaves are lobed, with bristle points at the end of lobe. The sinuses (the space between adjacent lobes) are much deeper than those of Northern Red Oak. Like the Northern Red, the Scarlet Oak has "ski trails" on the bark. Some people think they are narrower, but I've never been able to confince myselt that's true. The acorns have a faint ring around the end opposite the cap.
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| Part 1; End of a Scarlet Oak shoot. The other end is seen in the photo below. Both photos were taken by Susan Brown. |
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| Part 2; Scarlet Oak shoot This is the end of the shoot that was closest to the tree. |
Moving to Part 1. The gray objects you see at the base of most of the leaves are axillary buds, so called because they are in the "arm pit" of the leaf petiole. (Axilla is the anatomical name for human arm pit.) Axillary buds will usually give rise to leaves the following year.
Still in Part 1. At the very end of the branch you'll see a much larger bud. This is the terminal bud of the branch. Next spring it will give rise to a new shoot (branch) like the one we're looking at right now. (Or, it would if it were still connected to the tree.) If you coulc look into the terminal bud right now you would find next year's shoot in miniature -- every tiny leaf in microscopic miniature.
The next paragraph explains this more lucidly than I can, so you should read it, especially if I confused you.
Shoot Growth in trees:
The next paragraph explains this more lucidly than I can, so you should read it, especially if I confused you.
Shoot Growth in trees:
"Within the bud, two growth habits are possible, fixed growth and free growth. Fixed growth occurs in species such as pines, hickory, and oaks, where the buds contain a preformed shoot. All of the components of next year's shoot are contained in the bud formed this year; the number of leaves and nodes is predetermined by this year's environmental conditions. The length between leaves and nodes is influenced by the environmental conditions the tree encounters next year.
Free growth, in species such as cottonwood, willow, and silver maple, occurs when buds contain shoots with some preformed leaves, but which are also capable of forming additional leaves. These species can continue to grow as long as environmental conditions are favorable."
Source.
Shagbark hickory
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| Shagbark Hickory bark plates are loose at top and bottom. |
Shagbark hickory
Three Shagbark Hickories
grow in the shallow ravine between the Green and Blue trails. Their
shagginess is due to their bark's vertical plates turning loose at
both top and bottom and curling away from the trunk. White
Oak bark is also shaggy, but its
bark plates loosen along the side, not the top and bottom.
Shagbark nuts are much smaller that Mockernuts and have a
very thin husk compared to Mocckernuts thick husk.
Shagbark occurs in this
ravine because the soil there likely has a higher pH due to a band of
amphibolite that angles across the Garden from the nearby ridgeline all
the way to the river. Amphibolite is high in calcium and magnesium which
raises the pH of soils that develop over it. Calcium-loving plants
(calciphiles) such as Shagbark Hickory are often found over amphibolite
bedrock.
Blowdowns
There are a large number of "blowdowns" along the trails in the Botanical Garden. These are due to a large number of factors, but a prominant one is 19th century agricultural practices. They stripped the topsoil from the hills and now oak trees are only shallowly rooted, making them vulnerable to windthrow.
Windthrown trees create "tip ups," the term applied to the turned up root mass of the tree. The space occupied by the roots is now a pit and the soil adhering to the roots is a new microenvironment. The forest may have lost a tree, but it gained new habitat that can be utilized by a variety of plants and animals.
SUMMARY OF OBSERVED SPECIES:
Mockernut Hickory Carya tomentosa
Southern Red Oak Quercus falcata
Scarlet Oak Quercus coccinea
Northern Red Oak Quercus rubra
American Beech Fagus grandifolia
American Toad Bufo (Anaxyrus) americanus
