How to Read the Rocks Around Our Pond

The rocks around our pond have stories to tell if you know how to listen.  Thanks to Mr. Smail, our high school Geology teacher, for showing me how to read our rocks.  Here are a few of the amazing things I learned from him about the flat rocks that border the pond:

Rock # 6, my favorite.

ROCK FORMATION:

Our rocks are ANCIENT.  Middle Tennessee rocks were mostly formed 300-500 million years ago, during what is called the Paleozoic Era.  During that time, life was growing mostly in the oceans and just beginning to expand to land.  The area that would one day be called Tennessee was covered with a shallow ocean at the beginning of the Paleozoic Era.  Many ocean organisms in the Paleozoic Era produced hard shells made of calcium carbonate.  When those organisms died, their shells accumulated, compacted, weathered and eventually formed limestone, which is the type of rock we have in our outdoor classroom.  Many of today's ocean organisms also have calcium carbonate shells, so they are just starting to form limestone of the distant future.

Here's a map to the rocks around our pond.  The map has numbers so you can find the things I'll talk about here.  Feel free to print the map and draw or write your observations on it.

Map of rocks with numbers (zoom in to see numbers).

Many areas of our rocks are smooth limestone, like almost all of rock 19.  The smooth limestone was produced when the water above the forming rocks was calm.  The calm water washed tiny, tiny bits of shell onto the ocean floor that built up and solidified into smooth limestone.  Before the tiny bits turned into stone, they would have felt like smooth mud.  On several rocks, it appears the mud dried and cracked before turning to stone.

Rock 13 with smooth rock made from dry, cracked smooth mud.

Some areas of the rocks have larger particles and lots of fossils (see below).  These formed when the water was more turbulent and washed larger particles onto the ocean floor.  Rocks 1 and 2 are mostly made of larger particles.  If you've walked on a beach made of very rough sand, you know what sizes of particles formed this rough limestone.

Most of our rocks are made of the rough limestone mostly covered in a smooth layer of limestone.  Rocks 15 and 16 are different.  They were likely made when very turbulent water mixed big pieces of smooth limestone with large shell bits that cemented into rough limestone around the smooth limestone bits.

FOSSILS:

The signs of ancient organisms in rocks are called fossils.  Since limestone is made from the shells of ancient organisms, you can expect to find LOTS of recognizable fossils in our rocks.  The most common fossils in our rocks are shells of ancient clam-type organisms.  We have a few whole shells (Rock #2) and lots of c- or j-shaped fragments or pieces of shells (most rocks).  We also have fossils of long, segmented organisms called nautiloids.  Nautiloids were relatives of modern-day squids, and like squids, they were predators that chased down their prey.  There are always fewer predators than prey in an ecosystem, so it makes sense that there would be fewer nautiloids than clam-type shells.  Rocks number 6 and 17 have nautiloid fossils.

C- and J-shaped shell fossils in Rock #6.

Gorgeous nautiloid fossil in Rock 6, surrounded by shell fossils.

The fossils above are body fossils, or actual fossilized body parts of ancient organisms.  Another type of fossils, trace fossils, are fossilized evidence that organisms were present, like footprints or trails.  The light squiggly lines in many of the smooth limestone areas are trace fossils of burrows or trails left by soft-bodied organisms like worms.  Soft body tissues cannot form fossils, but we can learn a bit from trace fossils about ancient soft organisms.

Lighter squiggles are trace fossils, evidence that soft organisms were once present here.

NOTE TO TEACHERS:
Mr. Smail would be happy to meet your class at the outdoor classroom to answer questions if he is available - just email him.  Also, below is another map with a key to where you can find some of the features I mentioned above.  I thought you might want the students to make their own, so I didn't include it above.  Also, I'll discuss the big boulder rocks in a later post.

Map of some of the fossils and rock features around our pond.

Japanese Quince

Every year about now I put on a few extra sweaters, check the weather forecast for snow, and go outside to look for.....flowers??!  Yes, that's right: flowers!

Japanese quince flower and flower buds.

It's time for Japanese quince shrubs to flower, and they are a welcome sight on these gray winter days.  Our outdoor classroom's Japanese quince shrubs are by the sidewalk near the entrance to the parking lot.  You can't miss them right now, as they are covered in blooms.

One of our two Japanese quince shrubs.

Japanese quince shrubs have an extremely unusual strategy for finding pollinators.  Their flowers are bee-pollinated, but there are absolutely no bees out today!  However, if you've lived in Middle Tennessee long enough, you've learned that we tend to have the odd warm day here and there throughout the winter.  When the weather warms up, beehives send out scouts to see if anything is blooming.  And for warm January days, Japanese quince have a monopoly on the blooming business, so any bees that are out will pollinate the Japanese quince.

Flower buds on a Japanese quince.

You may have already figured this out, but Japanese quinces are from Japan.  They were brought to the United States as an ornamental and edible plant centuries ago.  In the US, they are a slightly old-fashioned but well-loved garden plant.  You've already discovered their ability to brighten a dark winter day, but they also produce useful fruit, called a quince.  Quinces are relatives of apples and pears, and some types of quinces are well-loved in Asian and European cooking.  The quinces of our Japanese quince shrubs are small, hard and bitter, but they can be used to make excellent jams and jellies.  If these flowers are pollinated, we'll have some quince fruits later in the spring or early summer.  Watch out - Japanese quince shrubs have a few thorns to protect their quinces.

A sedum blooming in January.

There is another strange bloomer at the outdoor classroom right now.  It's called sedum, and it's growing right in the middle of the waterfall above the pond.  Sedums don't usually bloom until later in February or March, so I'm not sure what this little plant is up to.  But plants have variations just like people do.  Where people might have different hair colors, plants might have different blooming times.  If January turns out to be a good time for this sedum to bloom,  it will make lots of seeds and pass the early-blooming trait on to the next generation of sedums.  Next year there will be more early-bloomers.

Meet the Juniper (AKA Eastern Red Cedar)

Middle Tennessee is known for its cedar trees.  We even have a state park called Cedars of Lebanon.  The trouble is, the trees we call cedars are actually a type of tree called a juniper.  Our cedars have all the plant parts and structures of junipers, yet we call them Eastern Red Cedars.  Names are difficult to change once we get used to them, but I'm going to call our cedars junipers in this post.  The scientific name of our Middle Tennessee junipers is Juniperus virginiana, meaning juniper of the Virginia region.

Meet one of the junipers at our outdoor classroom.

Junipers have a million interesting characteristics.  My favorite thing about them is the difference in their immature and mature foliage (leaves).  Their mature leaves are smooth, rounded overlapping scales like you see in the picture below.  Junipers' immature foliage is sharp and spiky.  The easiest way to tell if foliage on a juniper is young or older is to close your eyes and feel the difference.  Fortunately, junipers are evergreen trees, so this is a great time of year to investigate their foliage.

Mature growth on a juniper.

Below is a juniper tree whole foliage is almost entirely immature.  It is about as big as the juniper in the picture above, so it must be about as old.  Spiky immature foliage protects young junipers from being eaten by deer or other animals.  I noticed the tree below was damaged and had its main stem cut.  Perhaps the tree is maintaining spiky, defensive foliage in response to what must have felt like a big bite to the tree (if trees could feel).

Spiky immature growth on a juniper.

On the branch below, you can see both mature foliage on older growth and immature foliage on new growth.  You can also see the cutest, tiniest cones you ever saw on an evergreen tree.  Juniper trees have two varieties: just like humans, they come in male and female forms.  Males trees produce cones like the ones you see below.  Female trees produce slightly larger purple cone-structures we call berries (because they look like berries).  Female trees must be larger before they can produce berries, so I didn't see any berries on our juniper trees, but we should have some in a few years.  We'll have to wait a few years to find out if any of our junipers are females.  Juniper berries are technically somewhat edible, but they have such a strong flavor that they are used mostly as a spice or flavoring.

Male cones, mature growth and immature growth on a juniper.

Below is the real prize.  I found one of these at the outdoor classroom, and I'm not telling where - you're going to have to find it!  No, it is not a piece of gum that someone stuck in the tree.  It is a fungus called cedar apple rust.  It grows on junipers (ok, cedars) for half its life, and it grows on apple trees for the other half of its life.  On junipers, it forms brown hard globs for most of the year.  After a warm spring rain, each of the dimples in the brown glob will sprout a bright orange spaghetti-shaped strand (I'm not making this up!).  The orange things produce spores that float away on the wind, land on a growing apple, and make the surface of the apple look splotchy.  The apple-stage of the fungus then makes spores that float and land on a juniper.  And you thought human life was complicated!

Juniper with cedar apple rust.

Cirque de Squirrel

It's a good thing you know what squirrels look like, because I don't have a picture of a squirrel for you!  I wanted to write about them this week, but when I went to take pictures, they were gone for the day.  That's OK, though, because there is plenty of squirrel evidence visible in our outdoor classroom.  If you visit and don't see actual squirrels, look for clues instead.

Squirrels are messy eaters.  They unwrap their food, eat what's inside, then drop their food wrappers all over the place.  If you walk around the outdoor classroom and look down at the ground, you can see their food wrappers (complete with squirrel teeth marks) all over the place!  (You may notice that humans are also sometimes messy eaters - I picked up several human food wrappers out there this week.  Somehow human food wrappers are less adorable than squirrel-chewed walnut shells.)

Evidence of squirrels.

Another visible sign of squirrel activity is squirrel nests.  If you look to the top of the magnolia tree in the front yard of the beautiful building next to our classroom, you can see a squirrel nest.  Do you see it in the picture below?

Can you see the squirrel nest in the top of this tree?

Here is the squirrel nest a little closer:

Squirrel nest in the top of a magnolia tree.

Squirrels are probably the easiest topic for me to make interesting, because just about everything squirrels do is either hilarious, cute or annoying.  Here are a few fun things you might notice about them this time of year if you stop to watch them for a while.

1. Acrobatics.  Squirrels climb up and down all sorts of surfaces.  They are the only mammals that can climb down trees face-first, which they do by turning their back feet around as they descend.  Squirrels chase each other on mad dashes through the tree tops, often making great leaps from one tree to another like circus performers on a trapeze.  They also have a great high-wire act - squirrels commonly run across electric and telephone wires as easily as we run on sidewalks. 

2. Nest design.  Squirrels make extremely well-insulated nests in crevices in buildings or trees or constructed in tree branches or on top of bird nests.  They layer their nests with feathers or thistle or dandelion down (those feathery parts of the seeds).  When their nests are made of leaves, they can add layer after layer of leaves to make a hollow ball for sleeping.  The layers of leaves keep the rain out and the heat in.  Since squirrels don't hibernate, they need to keep their body temperature warm all winter, so their nests are important for keeping them warm at night, just like your nest, er, I mean, bed.  Look for squirrels carrying leaves or other materials to build nests next time you see one.  (You can try out a leaf nest for yourself.  If you layer about 50 tightly-packed leaves carefully over a balled-up paper towel then sprinkle water over the top, the paper towel is unlikely to get wet.)

3. Variety of Behaviors.  Squirrels are generalist feeders.  We always think of them as eating only nuts, but they also eat tree bark, berries and seeds.  Generalist feeders tend to have a much wider variety of behaviors than animals that eat only one thing.  Generalists must be curious about new food sources and adapt their food searching to a variety of challenges, which means their brains must be flexible and able to improvise.  Nothing against cows, but compare the variety of behaviors of squirrels to cows, and you can see what I mean.  Try making a list of all the things a squirrel does next time you see one.  I'll start: chase, dig, search in the grass, make a loud alarm call, climb up bricks.....

4. Problem Solving.  If you've ever had a squirrel figure out how to access the seeds in your bird feeder at home, you have seen the evidence of squirrels' ability to solve problems.  Once they locate a food source or nest site, they will try many new strategies to succeed in their plans to eat or build a nest.  Notice how ingenious this squirrel is at getting to what he wants despite human attempts to keep him out of the bird feeder.  Squirrels are an inspiring reminder to try many different strategies to succeed at a task.

5. Memory.  Squirrels have an unusually good memory for where they leave food.  They store food for the winter in a method called scatter-hoarding.  It's the opposite of how humans store food - all in one place in the kitchen pantry.  Squirrels leave little patches of food buried or hidden in hundreds of places, and they remember where they leave the food (they don't find their stashed food by smell - they find it by memory).  Scatter-hoarding is risky because squirrels can't guard all their food at once.  However, if their food is discovered and stolen from one location, they still have hundreds of backup locations that are unlikely to be raided.  Look for squirrels burying their food - the squirrel is almost 100% likely to come back and dig up that food later in the season. 

6. Deception.  I'm not condoning lying, but it sure is amusing to watch squirrels lie!  If a squirrel knows it is being watched by another squirrel, it will not actually hide its food.  Instead, it will pretend to hide the food by digging a hole, pretending to drop in a nut, and covering up the hole.  The watching competitor squirrel will be fooled, then the squirrel will go and hide the food in private so as not to reveal the hiding place.  It is easy to verify if a squirrel has lied.  Next time you see one bury a nut, go check and see if the squirrel has actually done so or if it has fooled you too.

Why Are There Cages of Meat in the Outdoor Classroom?

Note to lower-school teachers: please read this all the way through before you decide to share it with your students!  It was tough to figure out how many details to share for your audience.

Something is rotten in the State of Tennessee, and it just so happens to be right here in our outdoor classroom!  Unfortunately (or fortunately, depending on your perspective), the chance to see this first class example of rot will only be available for another few days.

Scientists will study anything.  And when I say anything, I mean ANYTHING!  Scientists know that even the strangest research topics can lead to useful discoveries.  For example, the discovery of new rainforest organisms can help lead to the development of new medicines, a protein discovered in jellyfish helps to grow better crop plants, and learning about the internal structures of spinach can help us build better solar panels.  The strangest details in nature can help humans change the world, so scientists study nature.  All of it.  Even when studying nature involves looking at dead organisms.  And that is why high school science students have left pieces of rotting meat in our outdoor classroom.

High school students studying rotting meat.

Decomposition (AKA rotting) is nature's way of recycling nutrients.  With no decomposition, we would have no new growth.  Decomposition is a familiar process, especially this time of year when leaves are piling up and rotting (if they are not raked up and removed).  Leaves decompose and break down where they fall, and if you don't rake them up, they will be mostly broken down into soil by spring.  Decomposed leaves return their nutrients into the soil, providing the nutrients for next year's growth.  In Middle Tennessee, we tend to have great soil because leaves from our trees decompose and add to the soil every fall.

High school student documenting the decomposition process.

Animals that die also decompose, just like plants.  Their nutrients are recycled into the soil and into organisms that use dead animals for food.  We are probably not as comfortable with the thought of animals decomposing because the sight of dead plants is so much more common than the sight of dead animals.  Also, the decomposition of animals can be a little smelly at times, since animals contain substances called nitrogen and sulfur, which are not present as much in plants.  Nitrogen and sulfur can turn into odorous compounds during decomposition (also noticed in the odor of urine (for nitrogen) and rotten eggs (for sulfur)).  But never fear - the smell isn't that bad, and it won't hurt you!  Go take a look to see what organisms are nature's recyclers of dead animals.

Animal-proof cage for decomposing meat, allowing decomposition to occur.

The high school science students have built two wire mesh test chambers for studying the organisms that decompose pork meat.  The wire mesh keeps out rats and vultures that might eat the meat before it can decompose.  The students placed the meat in the outdoor classroom last week, and they are now checking the meat daily and documenting what organisms they see on the meat (and you thought your homework was difficult!).  The teacher for their class tells me that the meat will be totally gone in a few days or up to a week and a half, depending on how warm the weather is.  The warmer the weather, the faster nature's recycling organisms will break down the meat.

Two tiny black ants summitted this mountain of meat, and beige-colored blowfly eggs coat the cut bone.

According to the high school teacher, there will be an enormous variety of organisms present on the meat over the next few days.  Mostly, there will be bacteria, which are microscopic organisms that live in and on the meat and break it down.  Bacteria will look like a white, beige or grey slime on the meat.  There will also be immature blowflies soon.  Blowflies look like metallic house flies, and they primarily lay their eggs in rotting meat.  The immature forms are called maggots, which look like fat, short, white worms.  In a day or two, you will be able to see maggots feeding on the meat (should you be so lucky).  Currently, there are a few ants on the meat.  The high school teacher tells me that ants usually show up later in the decomposition process, but I saw two ants that seem to have climbed to the top of the meat.  I thought they appeared to be very satisfied with themselves, standing on what must have been a mountain of food from their perspective!

If you wanted to investigate nature's recycling system for yourself, you could collect leaves or dead insects and monitor their decomposition in paper cups over a few weeks.  See what conditions are good for decomposition.  Is moist or dry better for rotting?  Will a dead insect decompose faster if it is sitting on moist soil or if it is alone in a dry cup?  Will dead leaves break down faster if they are open to the air or sealed into a cup with plastic wrap?  What about a leaf left whole versus a leaf torn into bits?  What leaves have decomposed more in our outdoor classroom - the ones in the pond or the ones laying around on the ground?  (See the leaf skeleton post for more on leaf decomposition.)

Why Don't Fish Need Mittens?

Brrrr!  It's been cold the last few nights!  Air temperatures dropped into the mid 20's, which is way lower than freezing.  I bundled up in many layers to survive being outside for about an hour last evening.  I felt a little bad for the fish in our outdoor classroom - they are stuck in cold water without any hats or mittens or even hot cocoa to warm them up.

A mosquitofish alive and well after several nights of freezing temperatures.

Humans are like tropical animals in terms of their thermal comfort zone.  We are comfortable living in temperatures in the 60's to 90's on the Fahrenheit scale.  We have created many devices to keep ourselves at a comfortable temperature: clothes, buildings, heat, air conditioning, insulation and ice cubes all help us maintain comfortable body temperatures whether we are in the tropics or in the Arctic.  Animals can be classified as endotherms or ectotherms, and we are of the endotherm variety.  Endotherms use some of the energy in the food they eat to keep their bodies warm.  Even though the temperature of the air inside our buildings is usually around 72 degrees, our bodies stay at 98.6 degrees.  Mammals, birds and even some fish like tuna can keep their body temperature warm using energy from food.

Mosquitofish are happy as clams in a much broader range of temperatures than we can stand.  They can live in the very warm water of shallow sunny pools in the summer, and they can survive a fairly cold winter too.  Mosquitofish are ectotherms, like most fish, amphibians, reptiles, insects and mollusks.  They don't keep their body temperature warm - they let it cool off when the environment cools off.  And as the temperature drops, they simply slow down.  Their bodies move more slowly, they eat less food, and they stay more hidden.  Many ectotherms hibernate, essentially sleeping in a cold state until the weather becomes warm enough to move around again.  If you watch our mosquitofish, you will notice that they are much slower on cold days than warm days. 

Mosquitofish can't survive if the pond freezes all they way through.  Fortunately for them, water temperature usually doesn't get as low as air temperature, so the pond is going to be warmer than the air temperature, and it won't usually freeze.  Also, ponds freeze at their surface, then the ice acts as an insulator, keeping the lower layer of the pond from freezing.  So even if you see ice on our pond this winter, it is likely that the mosquitofish will be swimming slowly in the water under the surface. 

Do mosquitofish feel cold?  I don't know.  I suppose you would have to put a mosquitofish in a fish tank with a cold area and a warm area and see where it chooses to spend its time!

Here are some other ways you can see organisms responding to the temperature at the outdoor classroom this week:

It's easy to see which plants survive freezing right now.  I'll write about this more in the deep winter, but it's probably easier to see now before the dead plants blow away and decompose.  The dead leaves in the picture below didn't survive freezing.  Either their seeds will survive the winter or their roots will survive in the ground, but it will not grow again until the spring.  The plant on the left is just fine with freezing temperatures, and it will stay growing, though very slowly, through the winter.  there are lots of winter-growing plants in our classroom.

The fern on the left survived freezing, the plant on the right did not.

The honey bees are still drinking at our pond on warm days!  They must have a fairly warm location for their hive.  Bees do some temperature regulation of their hives by eating food then shaking their wings really hard inside the hive to generate heat.  Our bodies do a similar thing - they shiver to generate heat.  Bees also flap their wings to fan the hive if it gets too hot.  Even though insects are ectotherms, bees have some endotherm ability.  Neat!

Honey bees are still drinking from our pond on warmer days despite the freezing nights.

A Visit From the Psyllid Fairy

What happens when you lose a tooth?  You get a visit from the tooth fairy.  What happens when you write a blog post about hackberry leaf gall psyllids?  You get a visit from the psyllid fairy!!!

Envelope of psyllids and leaf galls - what a great surprise!

A parent of a lower school student, and an accomplished naturalist, learned about hackberry leaf gall psyllids after bajillions of them emerged from the leaf galls of the hackberries around her house.  She had saved some psyllids to identify them and brought some to my mailbox in an envelope after she saw last week's post.  Here's what was in the envelope:

Two hackberry leaves with galls and five hackberry leaf gall psyllids.

Those tiny dots in the picture above are hackberry leaf gall psyllids.  The large brown things are hackberry leaves.  I decided to have a microscope photoshoot with the psyllids, so I used a camera with a narrow lens and held it up to the eyepiece of a microscope to take the following picture:

Adult hackberry leaf gall psyllid at 20x magnification.

The psyllid in the picture above is long dead and a bit dried out, but it still looks pretty good for a dead bug.  Psyllids are true bugs, and true bugs are insects in the group called Hemiptera.  Hemipterans have mouthparts that are good for sucking plant sap, which is what psyllids are up to when they are living inside leaf galls.  You can see the mouthpart of the psyilld pointing down from the head, which is on the left side of the insect.  You can also see one of its antennae pointing to the left of the head. 

Two dried hackberry leaves, each with a leaf gall.

This time of year, the above leaves are all the evidence you'll see of hackberry psyllids.  The adult bugs have hidden away in bark or in cracks around the outside of your house.

Many thanks to the psyllid fairy for the fabulous psyllids!