(Describer) Fog drifts through forests. Another forest burns.

[fast-paced music]

(Describer) A view looks up between trees, and the sun sets. In an animation, leaves and vines grow around letters that form the word "Forest". Title: The Forest Files. Titles: Quote: Come forth into the light and let nature be your teacher. William Wordsworth. Air Cycle.

♪

(woman) Trees matter in cities for everything from aesthetics, to habitats for animals, to clean air for us. Forests are just fascinating.

(Describer) Britta R. Hampton:

In photosynthesis, trees take in carbon dioxide, mix it with sunlight and water, and produce oxygen as a waste product. So the trees release oxygen, which animals take in, and we release carbon dioxide, and the cycle keeps going. They take in air through stomates on the underside of the leaves. In the leaves, the stomates bring in the air, which reacts with sunlight brought in by the chloroplast. The sunlight, the air, and the water combine to make glucose, which is the plant's food. The plant then releases oxygen as waste.

(Describer) William Carver:

Trees are just like us-- they breathe. They breathe in carbon dioxide, breathe out oxygen, which complements us-- it is the other side of the cycle from where we are.

(Describer) An illustration of the esophagus, lungs and heart turns upside-down. Green and brown are added to create a leaf.

♪

(Describer) Titles: Tree... In the arteries of your trunk, bring me together, Through your leaves, breathe out the sky. - Daniel Beaudry. Water Cycle.

The trees take in water through their roots, and as the water rises up through the tree and the tree uses it, it get to the leaves, where it transpires out through holes called stomata and enters the air. So the water goes from liquid to vapor, which enters into the air. Also, there's a change in weather patterns over forests. Forests either cool or warm, depending on the season, because of extra water above the ground. So when you go out into woods by fields, you'll often see mists. This has to do with how the forest is affecting the local temperature.

(Describer) Shadows of leaves cover the rough bark of a tree.

It's difficult for us to build a machine that works as efficiently as a tree in pumping water from the ground to its heights.

(Hampton) Forests are dynamic because they're always changing, whether it's growing new trees or old trees dying and falling. They are always evolving, always changing, which is part of their beauty and mystery. Why does it happen? What happens because of it?

(Describer) Titles: Quote: This is a story of circular infinity, of a planet birthing itself. Linda Hogan. Forest Lab. A man stands behind a small bonzai tree on a counter.

[fast-paced music]

Hi, I'm Martin, and welcome to my forest lab. Today we'll learn about the science of trees, plants, and forests. As we know, trees are a type of plant. If we're going to learn about the science of trees, we need to understand a bit about the science of water. How are they connected? That's an easy answer. Most of what's inside this tree is water. Whether it's this small tree or the big one in your backyard, trees are anywhere from 70% to 80% water. Let's start learning about the science of water. First thing we'll learn is water is very good at absorbing and holding heat, unlike air. To show a comparison, I have a balloon here filled with water and a balloon here filled with air. I'll hold each balloon over the candle. Let's start with the air balloon. When I hold the balloon over the candle, the heat goes from the candle into the balloon--pops it.

(Describer) He relights the candle.

When we try the same experiment with the water balloon, it'll be different. Check this out. I'll hold the balloon over the candle. And nothing happens, and nothing happens, and nothing happens. Looking in the bottom, it appears as if there's some carbon, but it is not popping the balloon. How does this work? Remember--water is good at absorbing and holding heat, so it prevents our balloon from popping. Let's relate this to plants and trees. As I said, most of a plant, a tree, a piece of celery, grass, it's made up of water-- 70% to 80% plus can be made up of water. So it's good at absorbing and holding heat. These are adaptations plants have to survive in their environment. Let's try other experiments relating to the science of water.

(Describer) He blows out the candle.

Two words-- adhesion and cohesion. Cohesion is when water sticks to itself. Water is sticky stuff. Those molecules are good at sticking or attaching to each other. Adhesion is when water sticks to something else. Let's go ahead and try a cohesion experiment. We'll place a penny on a plate, get an eyedropper, fill it with water. When I go ahead and slowly place some drops of water onto the penny, if you were to get down and take a look at the penny, you would notice that it's curved. The water on top is curved. That's because water molecules are attracting each other-- cohesion-- they're sticking to each other, and it produces what looks like a hill or ridge of water on top. Here's another experiment we can do-- again, to illustrate cohesion. Get a bucket of water and a paper clip. This experiment is a little tough. It may not work the first time. It may not work for me, but I'm going to carefully take my paper clip, place it on the water-- Hey, it worked! Good. It appears as if our paper clip is floating, but what's really happening is the water molecules underneath are sticking together and it's creating a layer, a skin, and it's making it difficult for that paper clip to break that surface and drop to the bottom, unless I push it, like this.

(Describer) It sinks.

Now let's talk about adhesion. Remember, adhesion is when water sticks to something else. I have two cups here. We'll put water into one cup, and then you'll need a string. Place the string tightly against the rim of each cup, and then make sure the string itself is tight or taut. We're going to slowly, even at an angle, pour water from one cup into the other. The water is sticking to the string. That's adhesion. It passes into the cup. Let's find out for sure. Did water go in?

(Describer) He pours some out.

Sure enough. Adhesion works. So how does this relate to plants? Plants and trees use and experience adhesion and cohesion. Here's another experiment. You can try this one at home. You'll need a jar, some water, couple drops of food coloring, and a piece of celery. Place the celery inside the water, and because of tiny little tubes inside the celery, or inside of any plant, blade of grass, or tree, the water moves up those tubes and we'll be able to see it as a blue line, blue liquid, inside our celery.

(Describer) Titles: Quote: The nation that destroys its soil destroys itself. Franklin D. Roosevelt.

[fast-paced music]

(Describer) Title: Soil Cycle.

(Hampton) The forest acts as a sponge and filter in many ways. It filters out impurities from the water and air, and those impurities are good for trees. As the tree absorbs those, it releases waste, which is actually oxygen that we use. Another way a tree works as a filter or sponge is it collects particles, collects nutrients, and holds the soil in place so runoff and erosion don't happen.

(Carver) The roots hold things in place. The roots themselves are large in a large tree. There's also smaller roots that break off of those, providing homes for smaller bushes and branches in woods.

(Hampton) They hold on to the soil. The roots have tiny little hairs that grab the soil, so it's difficult for soil to wash away. Regardless of slope or wind direction, trees and plants really do hold soil still.

♪

(Describer) Titles: Quote: The frog does not drink up the pond in which he lives. Native American Proverb. In the Forest Lab...

Hi, I'm Martin. Welcome back to my forest lab. Now we're going to talk about a dirty subject-- soil, dirt. Obviously, very important stuff for plants. Plants cannot survive without soil and dirt. Trees cannot survive without soil and dirt. Any type of plant must have this material to grow. There are many different sizes of particles making up soil and dirt. Some of them--way too large, boulders. Can't grow a plant well inside of boulders. Cobbles--much smaller. Pebbles--smaller still. Some plants will be able to survive in that. Sand--a smaller particle. Silt--smaller still. Finally, we have clay-- so small, you probably need a microscope to look at it. Then, there's one other thing added into soil, which is what all living things, plants, grasses, trees need to survive-- organic stuff, organic material. It's made up of other dead plants, other dead trees, other dead animals, microorganisms. In fact, speaking of microorganisms, there are a lot of them inside of soil, inside of this organic part of soil. In a single teaspoon of soil, depending upon where you get it, there can be millions or billions of microorganisms in one teaspoon of soil. Now we were talking a bit about particle size. I have some gravel over here. Specific types of trees will live in specific soil. It may be a mix of gravel and sand, maybe mixed with clay. As I said, it has organic material within it. But regardless of whether it's one type or a mix of particles, you always have space in between those particles. No matter how tightly they're packed, there's space between them. That space is important for the plant to survive because in between those particles, it's room for air and for water. For example, I have some pebbles in this tube, and I cram them down as tight as I can, but there's still more room inside of there. I don't mean the room here with no pebbles. I mean the space down here.

(Describer) He gets a pitcher. He pours water.

Check this out. I can pour water in, and keep pouring and filling and filling and filling. That space between the particles-- again, doesn't matter which particle you have-- is where the water would be and where air would be. Trees need both of those things to live.

(Describer) Water flows over rocks in a stream in a forest.

[fast-paced music]

♪

(Describer) Rolling hills are viewed from above clouds drifting by. Title: Dynamic Forest.

(Describer) Trees have yellow and orange leaves.

(Hampton) Forests are dynamic because they're always changing. They could be changing for natural reasons, or humans could affect them. Wherever the change comes from, it affects the forest. It's a fascinating concept to think that forests are not static. They don't stand still. They don't stay still. They're always moving and evolving and interacting with other organisms.

(Carver) They look stable to us, and we think of them as calm. But between themselves, they're waging a war. Like we compete with ourselves or with other creatures, trees use different techniques. They try to choke their friends or neighbors out, try to get the light before them. Some trees produce poisons from their roots to lay a kind of biotoxic waste in the area and keep other trees away. They use different methods for seed dispersal. Their intention is to cover as much ground as possible. So they have an agenda. It may seem peaceful to us because we're moving at a slower rate, but it's as competitive as any other living thing.

♪

(Describer) Title: Forest and the Weather.

(Describer) Dark clouds pass over trees.

Trees have a number of effects on weather. Ancient cultures thought trees produced the wind-- that they moved the wind by blowing, as opposed to the other way around.

(Describer) Carver:

Trees affect temperature, especially right around where they are, because they take groundwater up into their tree trunks and move it up out of the ground. That water in the air lowers the temperature in hot times and warms it in colder times. Because of that, we sometimes see a barrier between the open field and the forest itself, and that temperature change can cause a mist or fog.

(Describer) Fog drifts around treetops. Title: Weather and the Forest.

♪

[thunder rumbles]

(Describer) Hampton:

Natural disasters do have a big impact on forests, and it's not always a bad impact. Fire is an important aspect of forestry. Hard to believe, but some trees need fire to reproduce. Some cones are made where they will not open up and release their seeds unless they are surrounded by immense heat, which is kind of fascinating if you think about it. Other natural disasters-- windstorms...

(Describer) Wind blows tree branches and leaves.

snowstorms-- they're very good for forests because they get rid of old or dying trees. They knock them down, where they can become decomposing matter for bacteria. They can be homes for other smaller organisms. Natural disasters are wonderful in forests.

(Describer) In an avalanche, snow rolls down a hill into trees. In a thunderstorm, lightning strikes.

(Describer) In the Forest Lab, Martin:

Let's talk a bit about the weather. Weather is very important for trees to survive. Different types of trees will be found in different environments. And one reason they're different is because they have different weather patterns. Weather is caused when the atmosphere changes. As heat comes from the sun, it warms the atmosphere. When there are changes in the atmosphere, we have changes in the weather. Due to different weather in different areas, there are different types of trees. Tropical rainforest trees will not survive in the same type of environment as in northern North America. Let's create weather inside of this jar. We're going to make a cloud inside this jar the exact same way that clouds are formed outside in the environment. Clouds are formed up in the sky. The higher in the sky you go, there's less air pressure. So we'll put the ingredients in the jar, then decrease the air pressure. What are those ingredients? There are three. The first, of course, is air. Good. The second ingredient? Water. We'll put a couple squirts. Our third ingredient is what scientists call particulates, or particulate matter. That can include dust, dirt, smoke from forest fires, ashes from volcanoes. All those things would be called particulates, or particulate matter.

(Describer) He blows out a lit match and drops it in.

[blows]

We have all three ingredients inside our jar, but I don't see a cloud. Remember, clouds form higher up in the sky where the air pressure is less. When air pressure decreases, that's when clouds form. I'm going to hook up this cloud jar to a vacuum pump, which will remove, or decrease, the air pressure inside the jar. If you look, it looks kind of cloudy, kind of murky.

(Describer) A hose is attached.

That is a cloud. As the air pressure decreases, the water condenses, or sticks, onto the dust and our cloud forms. If we increase the air pressure,

(Describer) He disconnects.

the air goes back inside, our cloud disappears. But the ingredients are still in there. The air, water, and particulate matter is still in there. If hooked up to the vacuum pump again, the air pressure decreases, and there's our cloud. If you have enough water that condenses on a cloud, eventually those droplets become too heavy to stay on the dust particle and they fall. That's what we call rain or precipitation. When it rains, that means we've had a change in the weather.

(Describer) Outside, lightning flashes at night. In an illustration, a man chops wood by a log cabin under construction.

[dramatic music]

(Hampton) Humans have always been in battle with forests, especially when we came to the United States. There were an enormous amount of forests. Today, sadly, there are not as many. Human impact on the forests and in the United States has been a blessing and a curse in the same aspect. It's good because we have been able to use the trees for housing, for paper, for books, for lots of things. Trees are very useful to us. But when we tear down the trees, we disturb the ecosystem and the forest. Animals lose a place to live. Trees aren't reproducing to give us more oxygen. The bacteria have nothing to decompose. And it's kind of a vicious cycle when we tear down the trees. If there are no trees, the water has nowhere to go but downhill, which could cause erosion, runoff, a lot of other problems associated with floods.

(Describer) Floodwater goes up above the wheels of a truck.

Trees reduce flooding by the simple fact that they absorb water. The roots are enormous. Their little hairs absorb any kind of moisture they find.

(Carver) They get in the water's way.

(Describer) Carver:

The roots raise the ground, so the water is channeled through an area. As the leaves fall, they break up water flow. As the water or its flow is stopped, the materials the water carries drop out, because they're not moving as quickly.

(Hampton) If you cut down trees, you invite water quality trouble. You invite erosion, runoff. And if your soil is being eroded away, you can't plant new plants. The plants and trees, like we know, help clean our air and water. So if we chop down the trees and don't plan accordingly, then it's just a downhill spiral.

♪

(Describer) Titles: Quote: We must be the change we wish to see in the world. Mahatma Gandhi

(Describer) Forest and Humans. In the Forest Lab, Martin:

Humans can have a tremendous impact on the environment. That effect may not happen where the effect is occurring. That impact may actually occur much further away. Something we do in our neighborhood can impact trees and forests that may be 20, 30, 50, 100, 1,000 miles away. We can explore that impact with a model that I have right over here. This model can represent Anywhere, U.S.A. It may not look perfectly like your neighborhood, but hopefully some parts will look familiar. Maybe there's a farm, houses, a residential neighborhood, businesses-- maybe you live in any area that has boats and boating, maybe there's industry and technology where you live. All those factors can impact trees, the environment, and the plants around us, and the trees, environment, and plants very far away. Let's go ahead and see how. I have some food coloring in a little container here. Let's start with our farm. Let's say the farmer decides to put insecticide on his crop. So we'll go ahead and sprinkle some of our insecticide on the farm over here.

(Describer) A stream run by the farm's field.

Good. Next, let's say that in our neighborhood, Mom or Dad decides to put fertilizer on the lawn. So we'll go ahead and put some fertilizer. And maybe even the chemicals that are in the swimming pool accidentally spill and get onto the ground.

(Describer) He sprinkles food coloring on those areas.

Next, we'll go ahead and use our street. Our car releases chemicals. Those chemicals will end up in the street. Maybe you or your friend tosses a drink out the window. The chemicals in that drink end up in the street or grass beside the road.

(Describer) He sprinkles more down.

Let's say you're in a boating community. Maybe you empty out your ballast water or something spills over the side of the boat. And we can see it's already starting to impact the river or stream around us.

(Describer) He squeezes food coloring around the boat.

And finally, let's say you're in an area that has business, industry, and technology. Chemicals can be released in the air. Those chemicals can be released. Maybe they fall in the street, grass, or waterway that's near the business or industry.

(Describer) He sprinkles more coloring around.

So we have all these chemicals. And we can see that they're already impacting there in our river or stream, over here with the boats. But not much is happening upland, until it rains.

(Describer) He sprays water.

And the rains come down, and we can see the chemicals getting into the water there and spilling down towards the tree. And the chemicals from our car are moving down the street, into the lawn, into the water. And the chemicals in the residential neighborhood from the fertilizer or from the swimming pool, they're moving into the streets and down towards the water and over to impact the trees in our neighborhood. And it rains over here where the boats are, causing those chemicals to move out into the rivers or bay or ocean. The same thing is happening here with the industry. The rain will affect the chemicals released onsite, wash out the chemicals released into the atmosphere.

(Describer) The colors spread.

We can see that chemicals that were released in one area can impact the environment and plants and trees, sometimes hundreds, sometimes thousands of miles away.

[birds singing]

(Describer) Titles: Quote: It is not important how small the thing I must do is. What is important is that I must do it. Mahatma Gandhi. What You Can Do.

(Carver) First, be aware of the problem, that we have to be wise to the way we use our environment. There's only one world we live on. When it's used up, there's no more. Trees are pleasant to us, in that they will come back if we are kind to them, plant them, take care of them. Important things you can do, besides being aware-- recycling is important, being aware of the resources you use-- power, water, those things. Be reasonable about their usage, if possible. Those are things we can do now, every day.

(Hampton) Teachers don't just have to be adults. Middle-school children can teach younger children about reducing, about recycling. Middle-school children can teach their parents, their grandparents, their aunts and uncles about how they can save the planet, how they can prevent deforestation. Middle-school students have a wonderful opportunity to change the world. And it all starts by simply talking about the issues.

(Describer) Forests with autumn leaves cover mountains. Two bear cubs wrestle. A chipmunk looks around a moss-covered log.

(Carver) There's a relationship between all living things. We are composed of the same kinds of patterns. The materials in us are in all living things. We share something like 50% of our DNA with plants that are outside our window. So they're similar to what we are. Living closely to them, the materials we breathe out, they breathe in, the water that leaves us goes into the cycle. Sap in a tree will one day be in my blood and next day will be somewhere else. We're connected in a fundamental and important way. [choir singing in foreign language]

(Describer) Against the background of a green valley, titles: Producer: Angie Callahan. Editor: Kimberly Lyman. Science Educators: William Carver, Britta R. Hampton. Classroom Videographer: Jay Sanchez. Original Music: David Voightritter of S.O.A.P. Forest Lab Crew: Director: Daniel Harrell. Host Martin Fisher. Cameras: Ryan Bedell, Neil Grochmal, Jay Sanchez. Executive Producers: Brian Callahan WHRO, Moira. Rankin Soundprint Media Center. The Forest Files was funded in part by grant awarded by the Northeastern Area State and Private Forestry, USDA Forest Service to the Soundprint Media Inc, Beltsville, Maryland. Accessibility provided by the US Department of Education.

Accessibility provided by the U.S. Department of Education.