Looking Over Clover

To any person who has spent enough time sitting on a patch of lawn to get a little bored, the leaf in the picture below will be instantly familiar. 

One clover leaf.

It's a leaf of the white clover plant, and there is plenty of it at out outdoor classroom right now.  One clover leaf has three parts, which is reflected in the Latin name of the plant: Trifolium repens.  Tri- means three, and folium means leaf.  Repens means reclining, which this plant does well, as it spends its entire life within about 3 inches of the ground.  Clover leaves usually have faint white lines in them, and they are never heart-shaped.  Another common lawn plant called oxalis has leaves divided into three heart shapes, and sometimes people get confused about it.

A patch of clover.  See any lucky ones?

White clover has several claims to fame.  First, they are tough little plants, and they survive well on lawns even under heavy foot traffic, so they grow everywhere there is a lawn.  People who are sticklers for uniform-looking lawns consider the plant a weed, but many people value the plant for its ability to grow in harsh conditions where grass can't grow.  Second, clovers are known and loved for their sweet-smelling flowers, which are white or pinkish clusters on stems.  I bet you have made a flower chain from clovers before.  Bees love the flowers even more than humans do, and they make great honey from it.  The sight of clover flowers on a lawn should serve as a warning to wear shoes, since bees are likely to be on the flowers, and stepping on a bee will get you stung.  Clover's third well-known benefit is its value as a food source for animals.  Clover seed is often included in the mix of seeds farmers plant for growing cattle forage (the plants cattle eat).

A small clover plant with leaves, stems and roots.

Clover also has a secret.  Most people don't know much about the hidden power that makes clover so important in nature and explains some of its better-known characteristics.  If you dig up a small clover plant and look at the roots, you see something that is not usually present on plant roots: tiny lumps.  Those lumps are called nodules, and they are actually little areas where clover keeps its own pet bacteria.  The clover provides food and housing (and maybe even affection) to the bacteria in return for the services the bacteria provides to the clover.  The bacteria produce an otherwise almost unobtainable nutrient called nitrogen.  Nitrogen is a nutrient used to make protein - the microscopic parts of organisms that provide much of their actual structure as well as much of the machinery to conduct life's processes.  Other plants can only get nitrogen by absorbing leftover nitrogen from dead clover-type plants or from decomposing animals or animal manure, but clover has its own constant supply.

Root nodules on a clover - where nitrogen is fixed.

Clover's source of nitrogen means it can grow on poor soil where grass can't.  It also means it has a high nitrogen content, making it more nutritious than grass for animals to eat.  When clovers die, they leave behind richer soil with more nitrogen, where other plants can now grow.

Clover is related to bean-type plants (pinto beans, Limas, black beans, lentils, peas), and all types of bean plants have the same pet bacteria for making nitrogen (actually called fixing nitrogen).  This type of interaction between two organisms that live in close contact and help each other is called mutualism.   Can you think of other examples of mutualisms?

Have you ever found a four-leaf clover?  Sometimes the plant makes an error when growing its leaves, resulting in our four-leaf symbol of good luck.  If you look at a patch of clover for long enough, you will probably find a four-leaf clover.  If you do, press it flat between pages of a book for a week or so, then you can glue it to paper or press it between clear tape to preserve it.

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.)

What is a Leaf Skeleton?

Leaf skeleton floating just below the surface in our pond.

For some reason, floating leaf skeletons are most visible on gloomy days.  Perhaps the filtered sunlight doesn't glare as much off the surface of the pond, and the light-colored skeletons stand out against the dark background of the pond depths.  Needless to say, leaf skeletons are strikingly beautiful, and they are lovely to find on a gray day.

Leaves ranging from living to dead floating in our pond.  The dead ones are starting to decompose.

The pond in our outdoor classroom has many tall trees towering over it.  As summer turns into fall, it is going to fill up with leaves, and we will hopefully have lots more floating skeletons.  Ponds provide the perfect habitat for production of leaf skeletons, because they allow for fast decomposition of soft plant tissues.  Aquatic conditions provide lots of snails, insects and microscopic organisms that attack a leaf as soon as it falls, since a newly fallen leaf has lots of nutrients to feed pond organisms.  The organisms eat the softest tissues and leave the leaf veins behind, allowing us to marvel at an important plant tissue.

Leaf skeleton from a hackberry leaf.

Leaf veins are a part of the transportation system within the plant.  The veins in leaves connect through the leaf stems into the main plant stems and all the way down to the roots.  Veins in plants are network of tubes for moving necessary substances from anywhere in the plant to any other part of the plant.  My mind can't help but compare leaf veins to our system of roads.  All our houses are connected to them, and we can use roads to get anywhere else.  I also think of our system of blood vessels - a similar network of tubes for moving necessary nutrients from one place to another within our bodies.

Leaf skeleton showing network of veins.

Plant vascular systems (vein systems) contain two types of tubes inside each vein.  One type of tube, called xylem (pronouned zy-lum), is rigid and only runs in one direction.  Xylem carries water and nutrients from the roots in the ground up to the leaves.  The second type of tube is called phloem (pronounced flow-um).  Phloem tubes are soft and flimsy, and they carry sugar, the product of photosynthesis, to wherever energy is needed in the plant.  Phloem tubes run in two directions.

Leaf veins in living leaves.

Leaf skeletons can be preserved by drying them pressed between newspaper or paper towels.  Their patterns can be revealed by covering them with paper and making a rubbing.  Different types of leaves have different patterns of leaf veins - highly branched, long parallel lines or radiating out from a center.  All three of these patterns of leaf veins can be found at our outdoor classroom.  Another fun trick for learning about the function of plant veins is to place a white carnation in water with food coloring.  After a few hours to a day, the xylem will carry the food coloring up to the petals.  The same thing would work in a leaf, but the green color of living leaves would make it difficult to see the food coloring.