Our first ramble of the year started with 32
Ramblers including 1 new rambler and 1 guest. This is a record turnout for us.
Today's
readings
I read
an excerpt from Nature Near Home by
John Burroughs. This was one of Hugh's favorite passages. It reflected his
belief, developed over the years he led our group. I wanted to read it on this,
our first ramble without Hugh and Carol, as a tribute to Hugh's years of
leadership. (I've changed some words, replacing he and his with more
inclusive language.)
After long experience I am
convinced that the best place to study nature is at one's own home, on the
farm, in the mountains, on the plains, by the sea, no matter where that may be.
You have it all about you then. The seasons bring to your door the great
revolving cycle of wild life, floral and faunal, and you need miss no part of
the show.
At home you should see and hear
with more fondness and sympathy. Nature should touch you a little more closely
there than anywhere else. You are better attuned to it than to strange scenes.
The birds about your own door are your birds, the flowers in your own fields
and wood are yours, the rainbow springs its magic arch across your valley, even
the everlasting stars to which you lift your eye, night after night, and year
after year, from your own doorstep, have something private and personal about
them. . . . The wild creatures about you
become known to you as they cannot be known to a passer-by. . . .The traveler sees little of Nature that
is revealed to the home-stayer. You will find she has made her home where you
have made yours, and intimacy with her there becomes easy. Familiarity with
things about one should not dull the edge of curiosity or interest. The walk
you take to-day through the fields and woods, or along the river-bank, is the
walk you should take to-morrow, and next day, and next. What you miss once, you
will hit upon next time. The happenings are at intervals and are irregular. The
play of Nature has no fixed program. If she is not at home to-day, or is in a
non-committal mood, call tomorrow, or next week.
Next, Don read a short passage from John Muir's Travels in Alaska:
“In every walk with Nature one
receives far more than he seeks.”
Today's
route:
Leaving the arbor, we made our way past the
Callaway Building and Amphitheater to the mulched north end of the White Trail
Connector, and down to the Dunson Native Flora Garden. Leaving the Dunson Garden, we made our way
through the weed patch on the other side of the fence, then over to the power
line right-of-way, where we headed down the ROW towards the river, stopping at
a vernal pool. We returned via the ROW
and the south end of the White Trail Connector spur back to the parking lot and
on to Donderos'.
North End of White Trail Connector, leaving the arbor
parking lot:
We stopped to identify a young Sourwood tree, young
enough to have not developed the highly ridged bark that is typical of this
species. Linda pointed out that there were several root suckers at it's base,
which is an indicator that the tree is diseased or in other difficulty. She
also noted that the new shoots are reddish in color and that if you tasted them
they would taste sour. Emily, no surprise there, immediately broke off a twig and
chewed on it. Her conclusion: maybe or maybe not.
We took a quick look at an American beech with its
diagnostic smooth gray bark and long, slender sharply pointed buds, both
lateral and terminal. (Terminal buds are at the end of twigs; lateral buds form
on the sides of the twig.)
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| Hawk's nest in crotch of White Oak tree |
Then we heard the cry of a Red-shouldered hawk and Linda
pointed out the nest that is under construction in a nearby White oak tree.
Dunson Native Flora Garden:
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| Alleghany spurge (AKA Pachysandra) |
Entering the Dunson Garden we saw green leaves of
several herbaceous plants: Alleghany spurge, Columbine, a Trillium (probably
Trillium cuneatum) and White avens. Linda noted that the Alleghany spurge makes a nice, shade tolerant, ground cover. And, it's a native species!
Further along we stopped to look at the large,
fuzzy terminal buds of Ashe's magnolia. This suggested the question: what is
inside a bud? A bud contains an embryonic twig, complete with several leaves
and/or flower buds. In Spring a bud loses its protective scales, which leave a
scar on the twig where they were attached. By looking backward on the twig you can find the bud scar from the previous year and determine how much last years twig grew. After the bud scales fall off the newly revealed twig then begins rapid elongation,
sometime growing as much as a foot or more in the following few months. As the
twig elongates its embryonic leaves begin to expand. If there are any flower
buds present they also develop. Some terminal buds just produce flowers – they
show no growth after the flower develops. Other terminal buds produce flowers
at the base of their developing leaves and in still other kinds of plants flowers are produced on lateral buds.This is why you have to be careful about when you prune a shrub. Some flower on the new growth of the current year while others flower on the previous years growth.
Nearby the magnolias Roger pointed out a Green and
gold with a single yellow flower and
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| Sensitive fern reproductive fronds |
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| Golden ragwort with flower buds |
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| Golden ragwort overwintering leaves with leaf mines |
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| Sharp-lobed hepatica (AKA LIverleaf) |
Many plants, like the hepatica, have strange
sounding names, at least to the modern ear. Linda explained that these names
are often derived from the medieval Doctrine of Signatures. The
belief was that God had created some plants to resemble human organs that were curative of diseases affecting these organs. Hepatica got it's name from
the fact that the leaves have three lobes as does the human liver. (Hepatica,
in Latin, means liver.) Other examples of the Doctrine of Signatures can be
found in names such as Toothwort and Spleenwort (the suffix –wort is from old English and simply means
"herb" or "plant." The Doctrine of Signatures held sway for
centuries, probably as a result of a placebo effect and the fact that most
illnesses run their course for a week or so. If you get sick and wait a week
before you see a doctor you probably would have recovered without the prescribed medicine, but the medication gets the credit when you recover.
At the nearby bridge in the Dunson Garden there are
two young Sycamore trees that have wonderfully patterned bark in shades of
gray, green and white. When you see older Sycamores that colorful bark will
only be seen on the upper reaches of the trunk and limbs – the base of the tree
develops a more typical dark, ridged bark. The older the tree the higher up the
dark bark extends.
Linda pointed out a "Witches broom" on a
Hop hornbeam tree. This is a scraggly bundle of small twigs that emerge from a
short region of a tree limb. It is caused by an infectious agent like a fungus.
In the Botanical Garden we frequently find Witches brooms on Hop hornbeams, but
they can be found on other trees as well.
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| Leatherwood flower |
Notably we discovered that the Leatherwood shrubs
have started to bloom. Last year, near this time, we found honeybees visiting
the Leatherwood flowers, but none were seen today.
Along the path we sighted several Cranefly orchid
leaves. This orchid has the unusual habit of producing a single leaf during the
winter. The leaf ages and disappears toward the end of spring. Then, in late
summer, a flower stalk bearing dozens of tiny orchids emerges from the ground.
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| A Frost flower on the stem of a weed |
As we left the Dunson Garden Don led us on a hunt
for Frost flowers. The sun was barely touching the weedy hillside and there
were still a few that had not melted. (The Frost flower is not a flower – it is
an ice formation that is only seen when the overnight temperature falls below
freezing. Water is extruded from the stem of a weed and freezes into
interesting curving patterns that melt as soon as the air temperature rises
above the freezing point. They commonly are found on White crownbeard, also called, appropriately, Frostweed, but is less common on other plants.
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| An enormous puffball |
On the way out of the weed patch Don discovered an
enormous Purple puffball, almost as large as his head.
Flood plain, Power line right-of-way:
 | |
| Ramblers watching soaring vultures |
Several people spotted two kinds of vultures
soaring overhead: Turkey vulture and Black vulture. Turkey vultures have a keen
sense of smell and can detect the odor of dead animals even if they are hidden from
sight. They often are the first to discover carrion. The Black vulture will
often arrive late to the scene and displaces them from the prize the Turkey vultures discovered.
On the east side of the right-of-way there is a low
place where water often collects during
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| American toad egg strings the tiny black objects clinging to the jelly are hatched tadpoles |
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| Southern leopard frog egg mass |
While some ramblers were looking at frog eggs Linda
told us about a frog
call CD that is available from the Georgia Department of Natural Resources.
This recording and accompanying book will help you learn to identify the calls
of over two dozen frogs found in our state. Frog calls are easy to learn
because they are usually simple and stereotyped, not nearly as complex and
variable as bird calls can be. You can impress your friends and loved ones with
your ability to speak frog if you just purchase and study this CD and booklet.
You can also hear the calls of many Georgia frog and toad species (and Alligators) at this website.
You can also hear the calls of many Georgia frog and toad species (and Alligators) at this website.
Ephemeral
wetlands
The wet areas in the flood plain are ephemeral, meaning that they do not retain water all year. This intermittent dryness makes them attractive to amphibians, because it means that they do not contain fish. Fish prey on amphibian larvae and frog and toad tadpoles will have a difficult time surving in water with fish. But the temporary nature of ephemeral pools has a downside -- will the water remain long enough to allow amphibians to complete their development? These
standing pools of water form after rains, but they persist longer during the
winter and spring months. The same pools also form after heavy summer
rains, but they dry up very rapidly. The reason is not directly due to the higher temperatures of summer,
although that has an effect. It is the vegetation. The trees, grasses, herbs
and shrubs that grow in the flood plain are dormant during the winter but
actively growing in the spring and summer. As plant growth is renewed the water in the
soil is drawn up through the roots and carried to the leaves where it
evaporates. This is a process called "transpiration." This invisible
stream of water, moving through millions of root systems, carries with it
mineral nutrients from the soil up to the photosynthetic machinery of the
leaves where the energy of sunlight binds the nutrients into organic form. It
is the evaporation of water from the leaves that makes plant growth possible. Transpiration effectively pulls the water out of the soil. That evaporated water is replaced by water in the soil drawn from the water
table, so as plants grow, making more plant tissue, the water table must fall.
This is why water can accumulate in temporary pools during the winter and why
those pools must vanish during the coming spring.
The removal of the privet from the levee area of the Orange trail should have a huge impact on the retention of water in the flood plain. I previous years with rampant privet growth that area frequently dried up. It will be interesting to see how much water is retained now that the privet is gone. (Because privet is evergreen it continued transpiration during the winter months when native plants would be inactive.)
The removal of the privet from the levee area of the Orange trail should have a huge impact on the retention of water in the flood plain. I previous years with rampant privet growth that area frequently dried up. It will be interesting to see how much water is retained now that the privet is gone. (Because privet is evergreen it continued transpiration during the winter months when native plants would be inactive.)
The temporary nature of such wetlands makes them
especially attractive to amphibians. Because they are temporary, they do not
harbor predators like fish, making them good places for tadpoles to thrive.
What one hand gives the other taketh away. The frogs get a relatively secure
place for their offspring, but at the expense of forcing them to develop rapidly.
It's like finding an inexpensive furnished apartment and discovering that the
building is going to be torn down. It's not surprising that the frogs that
breed in this type of environment develop from egg to tadpole to adult in a few
short months. For some it is a race that is not won every year. Frogs with
longer developmental times, like the Green frog, Rana (Lithobates) clamitans, cannot successfully breed in
such wetlands. They require permanent water, such as is found in the Beaver
pond/marsh found next to the Orange trail in Garden.
The frog eggs stimulated a lot of questions that
I'll attempt to summarize and answer here.
Who laid these eggs?
Initially I thought that the large egg masses could
have been laid by either salamanders or leopard frogs. I took home a sample and
examined them under a dissecting microscope. I'm now confident that they were
not laid by salamanders and their subsequent development confirms this. First,
salamander eggs masses are smaller and don't have as many eggs. Second,
salamander eggs are generally larger that frog eggs and these are too small
(the egg proper, not including the jelly coat). So, if they are frog eggs,
which kind of frog laid them? The early breeding frogs in this area are
Southern leopard frogs, Spring peepers and Chorus frogs. Of these, peepers lay
their eggs a few at a time, scattered in the litter, Chorus frogs lay eggs in
small masses wrapped around grass blades and leopard frogs lay large masses of
eggs in shallow waters, wrapped around vegetation. So these are probably
Southern leopard frog eggs. The possible pond breeding salamanders in this area
are the Spotted salamander, Mole salamander and Marbled salamander. Of these,
the Marbled salamander can be excluded because they lay eggs in the fall, under
logs or leafy debris in areas that are likely to be flooded by late fall/winter
rains. Spotted salamanders gather in large aggregations for mating and the egg
masses that they produce are smaller than those that we saw, with larger eggs
and embryos.
The other type of egg mass, the coiled strands of
dirty jelly embedded eggs, is typical of the American toad, the early breeding
toad in this area.
The facts of life for frogs and toads and
salamanders
First, frogs and toads. When breeding season
arrives male frogs congregate in a suitable location, like a pond of small pool
of water, and begin calling to attract females. Those calls are species
specific, just as bird calls are. You can learn to identify frogs from their
calls. Female frogs are attracted to the voices of their own species and
migrate toward the sound of the calling males. As she enters the pond she
encounters a male who immediately grasps her from above, tightly gripping her
with his forearms, his hands balled up and squeezed into her arm pits. The
breeding pair, male riding on her back, will now be carried around by the
female, searching for a suitable place to lay her eggs. When she finds a place
she begins to extrude jelly coated eggs from her vent. As the eggs emerge the
male brings his vent close to them and emits sperm, fertilizing the eggs as they
emerge from the female. This process continues until the female has laid all
her mature eggs, which in some cases can number a thousand or more. Smaller
frogs usually produce a lower number of eggs – a hundred or fewer.
Salamander reproduction differs from frogs. In the
typical salamander fertilization of the eggs is internal, happening inside the
female's body. In most salamanders the males do not clasp the females. Males
produce a spermatophore, a short, gelatinous structure that is capped with a package
of sperm. The female walks over the spermatophore and picks off the top part that
contains the sperm. She then will lay several egg masses, somehow using the
stored sperm to fertilize them before attaching them to submerged vegetation.
Where does the jelly come from?
The jelly that covers amphibian eggs is produced by
glands in the oviducts of the female. As mature eggs leave the ovaries they
move through the oviducts and the glands secrete a jelly that coats them as
they pass by. This jelly is just a thin mucous layer that will absorb water and
swell up when the eggs leave the females body. In toads the jelly is produced
in a continuous cylinder that surrounds the eggs and when it leaves the body
becomes the a long string of jelly-encased eggs, one from each oviduct. As the
female toad lays her eggs she walks forward. The jelly coat is sticky and
adheres to sticks, grasses or twigs in the water and stretches out as she walks
away. Leopard frog eggs are individually wrapped in a sphere of jelly. As the
female lays her eggs she remains still and gathers her eggs with her hind legs
and presses them against grasses or other vegetation in the pool. As the jelly
surrounding each egg absorbs water and swells the eggs adhere to one another,
forming a single large mass.
How long before the eggs hatch?
The rate of development depends on the temperature
of the water. The lower the temperature the slower the egg will develop. Eggs
deposited in shallow, sunny places will experience higher temperatures and will
develop faster. That's probably why all the leopard frog egg masses we saw were
clustered together at the very shallow edge of the pool. It may take a week or
more for them to hatch.
How frog eggs are laid
The American toad lays its eggs in a pair of long
strings that can be coiled like the extension cord on a telephone handset (if
anyone remembers those). Ripe eggs emerge from the two ovaries (one on the left
and one on the right) and pass into the two oviducts that will encase them in
the jelly coating. As the eggs pass down the oviduct they are encased in a thin
layer of jelly secreted by glands in the oviduct walls. As the egg strings
emerge from the body of the toad they are fertilized by the male that is
clasping the female. The jelly-coated egg string rapidly absorbs water and
swells to form a thick, viscous cylinder that surrounds each of the eggs. As
the female toad lays her eggs she walks forward. The egg string sometimes
catches on vegetation and stretches out as she goes. If it doesn't catch on
anything it gets dragged along and the jelly picks up a coating of mud and
debris from the floor of the pool. That's why it is hard to see anything inside
the jelly strings/cords that we saw this morning – the jelly coats picked up a
lot of mud.
The Southern leopard frog egg masses appear to be
more recently deposited than the toad eggs. I base this conclusion on the
relative developmental stage of the embryos. The toad embryos have reached the
tail bud stage whereas the frog eggs are earlier embryos – their nervous system
has begun development but the tail bud has not yet emerged.
The difference in the appearance of the egg masses
is due to two things: the way the frog lays its eggs and the way the jelly is
produced. The leopard frog female remains stationary and as the eggs are
extruded and fertilized she keeps them together with her hind legs instead of
walking forward like the toad. In addition each egg is coated with an
independent jelly coat instead of being imbedded in a long cylinder of jelly.
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| Leopard frog embryo still encased in jelly envelope |
The Leopard frog egg jelly envelope in the photo above is 1/4 inch in diameter. The dark object in the middle of the jelly sphere is the frog embryo. The head is beginning to form (on the bottom side of the photo) and the beginning of a tail bud is forming on the other end.
The photo above is of an American toad embryo that I removed from its jelly envelope. The head is to the left, the tail bud toward the right. The embryo is only about 1/8th inch long at this stage of development. It's growth is supported by the yolk present in the egg. The remnants of that yolk are seen in the slightly swollen belly. The bump at the bottom of the head is an adhesive gland that will allow the embryo to attach itself to objects in the water after it has hatched but before its development as a tadpole is complete. At this stage of development the eyes are beginning to form and the embryo can only twitch a little if it is touched. Toad development proceeds more rapidly than Leopard frogs. The toad eggs I photographed on Thursday have all hatched by now (Sunday AM) but the Leopard frog embryos are just now showing elongated tail buds.
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| Toad embryo |
If you have other questions about frog and
salamander reproduction don't hesitate to ask me.
Back to the arbor on the White Trail Connector
Trail
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| Rue anemone |
One of the other surprises was the discovery of
some blooming Rue anemone flowers at the beginning of the trail. This area
supports a large population of Rue anemone, but we have never seen them
blooming here this early. The common name of this plant is strange to most people. The "Rue" is a reference to another plant, Early meadow rue, that has similarly shaped leaves. Thus this is an anemone with leaves that look like a rue.
SUMMARY OF OBSERVED SPECIES:
Sourwood
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Oxydendrum
arboreum
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American beech
|
Fagus
grandifolia
|
Red shouldered hawk
|
Buteo lineatus
|
Alleghany spurge
|
Pachysandra
procumbens
|
Columbine
|
Aquilegia
canadensis
|
Trillium
|
Trillium
cuneatum.
|
White avens
|
Geum
canadense
|
Ashe's magnolia
|
Magnolia
ashei
|
Green-and-gold
|
Chrysogonum
virginianum
|
Sensitive fern
|
Onoclea
sensibilis
|
Sharp-lobed hepatica
|
Anemone
acutiloba
|
American sycamore
|
Platanus
occidentalis
|
Hophornbeam
|
Ostrya
virginiana
|
Cranefly orchid
|
Tipularia
discolor
|
Leatherwood
|
Dirca
palustris
|
Painted buckeye patch
|
Aesculus
sylvatica
|
Purple-spored puffball
|
Calvatia
cyathiformis
|
Turkey vulture
|
Coragyps
atratus
|
Black vulture
|
Cathartes
aura
|
Southern Leopard frog
|
Rana
(Lithobates) sphenocephala
|
White tailed deer
|
Odocoileus
virginianus
|
American toad
|
Bufo
(Anaxyrus) americanus
|
Eastern bluebird
|
Sialia
sialis
|
Violet
|
Viola
sp.
|
Rue anemone
|
Thalictrum
thalictroides
|
