To start the experiment, the U.S. Forest Service cut some of the forest. The logs and brush were left to decay. Other strips of forest were also cut but the logs were removed. Some forest strips were left undisturbed to serve as experimental “controls,” which are used in experiments to find out what happens if no changes are made.
Robert Pierce, manager of the forest experiments, had talked to Herbert Bormann, a forest ecologist, and Gene Likens, a freshwater ecologist or limnologist. They needed a small watershed to study nutrient cycling. Pierce agreed to let the two ecologists make use of the forest cutting experiments for their own specialized studies. And so, in 1963, began a cooperative research effort by the United States Forest Service and professors from a private university.
The two ecologists were excited about this outdoor laboratory. Hubbard Brook Forest seemed made for ecologists to study. They could measure everything entering from the air and leaving this forest by way of the streams. They could analyze and compare the experimental strips with the untouched forest. How would the changes made to the strips of forest affect the plants, animals, soil, and water in those same strips?
To you and me, the Northeastern hardwood forest seems filled with red maples, sugar maples, birch, alder, beech, and ash trees that tower over our heads, and hobblebush branches that grab at our ankles while we walk on the spongy, often moss-slippery, leaf-covered forest floor. The forest is a quiet, cool, green room protecting us from raucous city noises and the hot summer sun. The plants pour clean oxygen into our lungs, free from from sooty city contaminants and smells. The fragrance in the air is fresh and natural. No aerosol woodsy scent is needed here. The forest becomes a place to be alone, to meditate, to observe animals, to discover flowers and berries, to hike and share a camping experience with friends. What are the things you like to do alone or with friends in the forest? Some of those things may be what ecologists do. But ecologists do many things no one else would think to do.
Bormann and Likens saw the forest watershed as several ecosystems. Each drainage basin with its own small stream was an individual ecosystem, a small part, a piece, of the whole earth’s biosphere or “life” sphere—that part of the earth’s land, water, and atmosphere where life can exist. Ecologists look for interrelationships—happenings between the living parts and between the living and nonliving parts in an ecosystem. They look for cause and effect—interrelationships that cause change or balance in an ecosystem.
Let’s take the word “ecosystem” apart. “Eco” comes from the Greek word meaning “home.” A “system” means many parts working together to make a bigger whole. “Ecosystem” is the way things work together to make a home for the plants and animals, the organisms that live together.
You yourself are an example of a system. Your lungs, heart, blood, and blood vessels are parts of your respiratory and circulatory systems. Working together, the parts of the systems get needed oxygen from the air to all parts of your body and return your gaseous wastes to the air. Added to all your other parts and systems, they make one larger living system, namely, you! If any part of you doesn’t work well, the rest of you may feel sick. It may take a physician to help get your systems running well again.
If the breakdown of any major part in a human system is so severe that the other organs or body parts can’t do their jobs properly, the person may die. And so it is with the living community of plants and animals. These are organisms that are only parts in larger working systems—ecosystems and the biosphere.
An ecosystem includes everything—the amount and intensity of the sun’s rays (photons); the air and water with their varying temperatures, gases, and chemicals; the rocks and soil with their varying temperatures, depths, hardness, and permeability; all the living organisms and dead materials. Everything that is in an ecosystem is part of that ecosystem.
Whether an ecosystem is in a habitat described as desert, as grassland, as evergreen forest, as deciduous or hardwood forest, as ocean, sea or high mountain, as Arctic iceland or tundra, as lake, river, pond, or fishbowl, the ecologist tries her best to look closely, observing, examining, and learning about everything within the boundaries of the place she has decided to study. She wants to learn how the ecosystem functions—how all the things in this one place work together and affect each other. “In what ways is this ecosystem changing?” “Is this life system balanced in a climax stage so that everything keeps living and appears to stay the same?” Or, “Is this system dying or dead?” the ecologist asks herself.
To learn how an ecosystem is changing, ecologists must know its past history as well as its present state. Then they can predict its future.
As the ecologists looked at the Hubbard Brook watershed, many questions filled their curious minds: What was the forest, the weather, the lake and the soil like long ago and in the more recent past? What do the streams carry away with them? What plants and animals used to live here? Are the same organisms here now? Did the different groups of people that have used this area make permanent or impermanent changes?
Watching the leaves quiver, hearing their rustling, rain-like sound, the ecologists wondered what was happening in the forest today. What changes, if any, were taking place in the air, the soil, the streams, the lake, the plant cover, and the animals that might cause the environmental conditions to alter the plants and animals that could exist here?
To see what was happening in this Northern hardwood forest now, what had happened in the past, and what might happen in the future, Dr. Likens and Dr. Bormann needed X-ray ecology eyes. They would have to see through things to what was happening. Questions and answers—finding causes and effects by recorded measurements and observations—would give them X-ray vision into forest happenings.
The scientists would be able to find the answers to some of their questions. But it would take more than their two lifetimes to answer all the questions. Impatient, they wanted to know facts about the forest and see what was happening in a shorter time. It takes long daily hours of work to do the measuring, counting, and recording of data that would eventually answer the questions. Lots of bits of facts must be fitted together to tell the story of a “happening.” Also, it takes lots of muscles and energy to collect the measurements. An ecologist may have to climb trees or mountains, wade up streams, or row across a lake to take measurements. These two men just didn’t have the time and energy to do the whole job of learning what was happening in the Hubbard Brook ecosystem.
But they could learn a piece of what was happening. They would do what they could. Later, others could do more and the early pieces of information would help them.
Where to begin? The forest was complex, its parts interwoven like the threads of a colorful Navajo rug. And the ecologists wanted to see the overall patterns in the forest the way you see the pattern in a rug. To sharpen their thinking and to help their eyes see the pattern rather than individual threads, they kept in mind a diagram.
Ecologists study what is happening in a community, how one thing affects—changes or doesn’t change—something else. They may diagram this with arrows to show the action between the elements or parts of the environment. Only two arrows are needed in the diagram to show action, because all the action or changes in any environment can be classified into one of two groups or categories—energy or materials.
Energy is the ability to do work. As work is done, energy is changed to a less organized and usable form. The sun’s rays give the earth its original life energy.
Plant leaves are the factories. Their green chlorophyll captures the sun’s light energy and uses it to combine carbon and oxygen from carbon dioxide (CO2) in the air with hydrogen (H) from water to create a sugar (glucose) that is stored in parts of the plant for future use. This chemical process is called photosynthesis, and we are still working on replicating it for our own use.
Plants use their own stored sugar for their own living activities. But there is a sugar surplus that animals can use after they eat the plant. By way of a plant and animal food chain, the stored energy from the sun is passed to human beings, keeping them alive, growing, mending, and reproducing. Extra energy is stored in our bodies as fat, ready to answer the energy needs of our bodies. When we run, jump, play the piano, or think, our body chemicals can change our stored energy—the fat—to other chemicals that give the quick energy needed by our muscles to do work, or the energy needed by the cells in our body to grow, mend, or perform their jobs.
The stored energy we give our automobiles is gasoline. When the supply of gasoline is gone from the tank, our car won’t budge on the level unless we use our own energy and push it. An ecosystem needs food energy to keep it running, just as a car needs gasoline.
Every ecosystem has (1) energy stored for future use, (2) energy that is changing its form, and (3) energy that is being used to do a job. In the process or act of being used or changing form, some energy is changed into heat and rises into the air, lost for future use on earth. Energy and its ability to change forms help people to jump, cars to go, and ecosystems to function.
The material that makes up all life is limited or finite. Atoms that join together to make carbon dioxide, nitrogen, oxygen, water, calcium phosphate, and other materials upon which plant and animal life depend are limited in number.
All the materials of the earth can be found in gaseous, solid, or liquid form in the atmosphere, or on and in the soil and earth. The same materials move around or cycle from place to place or from form to form in an endless chain. Without the processes to build up and tear down, thus changing forms, all the elements would get tied up in trees, animals, rocks, and clouds and stay there permanently. Life would be a statue rather than a motion picture.
Parts of a rock dissolve in the stream water and enter a plant by its roots to become part of a tree, perhaps an acorn that some busy squirrel eats. A fox makes a meal of squirrel and the phosphorus from the rock now helps the fox live. Perhaps fox is caught in a trap and dies. The bacteria, insects, and other soil creatures help move the “foxy piece of rock” into themselves or back into the soil for a new plant to use.
Earth’s materials move around from one place to another as if they were loaded into boxcars on a toy railroad track traveling from one stop to another, where some elements get off and other elements get on. Eventually the boxcars return to their starting point, having completed a full circle and made a system for moving materials. This endless chain is like your respiratory or circulatory system.
You can compare earth materials to bricks or a child’s building blocks. One time the blocks may form or shape a castle. Torn down, the same blocks can be used again for a bridge. Torn down repeatedly, they may in turn become a wall, a tower, or eventually another castle. The chemicals found in our biosphere cycle in a similar manner. One day materials may be part of a cloud, another day part of a river, an ocean, a tiny plant in the ocean, a small fish, a tuna, or you who ate the tuna fish. You perspire and a bit of heat leaves your skin as it helps the water droplets to evaporate, returning to the air and a cloud.
Energy makes it possible for the earth’s materials to cycle and change form. Energy pays the price for changing the form of materials. Whenever a frog turns into Prince Charming, some energy is lost into the atmosphere as heat.
To get a better idea of this magical change of forms, let’s follow a fly. Buzzing about a frog, fly gets stuck on frog’s long tongue and is soon being changed by frog’s stomach juices into frog. But frog doesn’t get all the energy that fly had originally. Fly had used some of its energy to change grass into fly and to live. The stored energy left in fly is passed on to frog, minus the energy needed to break fly down into building blocks that could become frog.
You may eat cereals and beef, but you don’t look like a cornflake or a steak. Your body juices digest these nutrients, breaking them down into small molecules. Your stored energy makes it possible for your body to reassemble the small bits of chemicals into you.
Materials changing form with the help of food energy is the basis for food chains—an important “happening” in any ecosystem. The grasshopper eating grass is in turn eaten by a frog that is consumed by a snake that is taken by a hawk that loses out to a bobcat that is trapped by man and becomes carrion, or dead animal material, for part of the earth’s clean-up squad, the vultures. Each link in this or any other food chain is forged by energy.
With their flow chart of energy arrows and material, or chemical, arrows, the ecologists could follow the action—the way materials and energy moved in their ecosystem study.
Where does one start piecing a forest ecosystem puzzle together? As with any picture puzzle, put the pieces you recognize together first, and as the picture grows you recognize more pieces.
Herb Bormann, the botanist and forest ecologist, would study the plants.
Gene Likens, the freshwater ecologist or limnologist, would study the streams, ponds, lakes, and rivers. A limnologist studies all about water that is not salty. As an aquatic ecologist Dr. Likens studied salty water too. But at Hubbard Brook only fresh waters were present.
Both men were college teachers and had students who wanted to tackle problems and find answers to questions about plants and fresh water. The professors had more questions than time to find answers. They wanted their students to have good experience learning to do research that interested them, so the students helped form questions and gather data.
The principal investigators were more than ecologists. They were also dedicated to teaching. They felt that individual research freedom—freedom to choose and develop one’s own project—would most help the whole study and at the same time give the best in graduate education. After the students assembled their data, the professors helped them analyze, interpret, and explain the facts they had gathered.
Other scientists learned about the Hubbard Brook study. New parts of the puzzle were worked on as other kinds of ecologists asked their own questions. The ornithologists studied the birds and then, studying insects, acted as entomologists. A paleobotanist was invited to core the lake bed and delve into the plants of ancient times. A herpetologist selected a salamander problem but also looked at the other “herps”—the reptiles and amphibians. A mammalogist studied the furry, hairy mammals. Another entomologist identified the insects. And an ichthyologist fished to get his specimens.
The researchers liked working at Hubbard Brook because they could pool their data. By sharing information, each researcher could make use of everyone’s data to develop or compare their own study and their own results.
At any time of the day or evening, researchers living at Pleasant View might be found on the porch working—reading, writing, or talking together about research problems. The porch was also a fine place for relaxing and chatting with the friends or family who came to visit.
Some of the student researchers worked on research problems that resulted in a master’s thesis or doctoral dissertation required for their own advanced college degrees. Other students gathered data for the principal investigators’ research projects. The researchers used first names. Where you might become confused by three Daves and three Toms or misidentify people, last names have been added.
Herb Bormann had students and assistants—Bob Muller, Peter Marks, Tink, Patsy, and Don—to help piece the ecosystem puzzle together.
Some of Gene Likens’ students from Cornell University were Dave Gerhardt, Dave Mazsa, Penny, Joe, Jim Gosz, and Tom Burton. Another Tom, Tom Baker, a Cornell undergraduate student, was hired by the ornithologists. Bernard became an Evergreen College, Washington, student and worked for Dr. Likens and other researchers. He did a variety of jack-of-all-trades jobs, as did some of the other students.
Dr. Richard T. Holmes, called Dick, was within a two-hour drive of Hubbard Brook at Dartmouth College, New Hampshire. Frank Sturges, from Beaver College in Pennsylvania (now Arcadia University), spent his summers in New Hampshire with his wife, Pat, and daughters, Sheryl and Karen. Helping these two ornithologists with the bird and insect studies, or working on their own studies, were Dartmouth students Ian Law, Craig Black, Gary Potter and a third Tom, Tom Sherry. A third Dave, Dave Zumeta, was a Haverford College student. Dorothy Willwerth, called Dot or Dottie, was a Beaver College student. Both Dot and Dave were hired to help the ornithologists.
Dr. William Reiners, called Bill, a plant ecologist from Dartmouth, studied the new growth in the experimental cut areas and hired people already at the Brook or from Dartmouth to help with his leaf counts.
Needless to say, there were many more students, professionals, and visitors who peopled the Hubbard Brook project than can be mentioned. But these are the principal players in the pages that follow. Knowing where they came from and why they were there may help you identify individuals as they appear in the scenes at Pleasant View, Mirror Lake, and the Hubbard Brook Forest.
Within ten years Hubbard Brook became a cooperative ecological research center. The National Science Foundation granted money to pay some salaries and buy needed equipment and materials for the special projects submitted to them and approved.
As the studies progressed, Bormann and Likens turned their attention to an energy and nutrient budget for the entire system, pulling together everyone’s research efforts. Now they wanted to know how much energy and nutrient material came into and moved out of the ecosystem. They wanted to know where the energy and material that stayed in the ecosystem were located.
An ecosystem budget is something like a bank account. If more money comes in than goes out, your savings account grows. If more money goes out than comes in, you may go bankrupt and your account dies. If the same money that goes out comes in, your account is stabilized and stays the same. Would the ecologists find the ecosystem being studied at Hubbard Brook mature and stabilized in a climax condition, in a growing stage, or dying? Energy and material budgets should tell the answer.
