The SimForest Teacher's Guide
By Esther Shartar
Contents
This teacher's guide consists of 3 units. The first, Tree Trunks, Leaves and Branches, is meant to introduce students to the tree biology, anatomy, and identification through field and classroom work. In the second unit, Trees in Forests students learn how to survey forest plots, and in the third, Forest Growth and Change, students learn how to use the SimForest software to investigate questions about forest dynamics.
Though the activities are broken up into numbered units according to type, we suggest that teachers do not keep the three completely separate. Because different students will come to these activities with different skills, interests, and background (e.g. some students may be most interested in tree biology, others in mapping a plot, and others in using the simulation), interspersing the activities from the different units may help to keep many types of learners engaged. Also, each unit may become richer when used in conjunction with the other two. However we do recommend that students have some class experience with real forests (Unit Two) before working with the software (Unit Three).
Because questions are such an important part of inquiry, this guide is structured by questions. Each discussion or activity is headed by a question, such as "How do trees make wood?" "How do you measure the size of a tree?" and "How does a forest change over time?" Under each of these headings are two lists, one of goals, and another of questions that relate to the topic question that may help students to build a deeper understanding of concepts and develop inquiry skills. The guide also includes teaching tips and background information to help teachers encourage inquiry and lead discussions and activities surrounding the questions.
We do not expect teachers to use the questions in this guide as a drill, in which students are meant to respond with the correct answer. Rather the questions are intended to help students take part in the process of forming theories and hypotheses, designing investigations, reviewing theories in the light of data or past experience, and asking their own questions. This does not mean that the correct answer is never important. Unit One contains a number of questions that are meant to help students develop understandings of specific concepts. However even in these activities we try to phrase the questions in a way that emphasizes the process of developing a concepts not just on the concept itself. For each activity teachers can decide how much emphasis to put on content, and how much on process.
One way that teachers can facilitate the inquiry process is by resisting the temptation to answer questions and correct wrong answers. Rephrasing questions, asking new ones, and gently pointing out the flaws in student theories (by asking a question whenever possible) may help students construct valid explanations themselves. However, there are times when a teacher may decide to give hints, suggest other resources or methods, and even answer questions. Such decisions can be made in consideration of the nature of the questions, the teacher's goals for the activity/ discussion, time constraints, or student morale.
Within each of the questions we suggest there are many different ways that an investigation could go, depending on the interests and questions of the students. Some questions and suggestions may even cause the class to pursue topics different than the ones with which it began, and this can be an appropriate outcome as well.
The questions in this guide are by no means meant to be limiting. We encourage students and teachers to use our suggestions or to come up with their own questions to pursue using SimForest or another investigation technique. This guide includes activities aimed at helping students brainstorm questions and design investigations. There is also on the last page in which teachers can record interesting investigations that take place in their classrooms in order to send them on to us and/or refer to them in future courses.
The questions we suggest can serve as examples of questions that may be asked or investigated by a class, and a standard by which teachers can assess their own and student questions. This may be especially useful in Unit Three when students are using an unfamiliar tool: the SimForest software.
Unit One: Tree trunks, leaves, & branches
The questions and activities in this unit are meant to stimulate students' interest in trees by introducing them to some fascinating concepts of tree biology, such as the way trees grow by adding a new layer to the outside every year, and the fact that trees make wood out of carbon dioxide and water. Students participating in the discussions and activities in this unit may learn skills and information, such as how to identify a tree, and what factors that affect tree growth, that will help them carry out plot surveys in the forest and investigations with SimForest (Units Two and Three).
Some activities in this unit involve interaction with trees and tree parts, some discussions, others book or internet research, and many a combination of the three. More than one group of questions may be addressed per class period, though some periods may be devoted to examining one question. For example, the questions "How does a tree make wood?" "If wood is made of sugar why can't we eat it?" and "Other than air, water and light what else do trees need?" might fit well into the same lesson, while the question, "Which type of trees grow around here?" could fill an entire class period or more.
All questions and activities in this unit are meant to spur inquiry cycles that involve actual and/or thought experiments. We hope that by encouraging students to work together and participate in class discussions, students will be able to learn from and build on one another's inquiry cycles.
Any of the questions in this unit may be asked in order to lead students towards a new concept, but many may also be raised by students. The questions do not need to be addressed in the order listed here. There are many different ways to structure this unit based on teacher preference and student interest. There is also plenty of room to explore of other questions (asked by you or your students) that are not listed here. Following up on student questions, in class or through homework, is not only an important step in the inquiry process; it may also improve student motivation and lead to some very interesting investigations.
To emphasize the importance of student generated questions, this unit begins by asking students to ponder and communicate what they know and do not know about trees, and to create a list of questions about trees. You may want to have students keep a journal throughout this and the other units, in which they take notes, record data and vocabulary, keep track of the questions that they have and document the investigations they undertake.
What is a tree?
Goals
Other Questions
  • Students will be able to ask questions, design investigations, and summarize their knowledge of trees.
  • Teachers will also gain a better understanding of student knowledge and interests.
  • What do you know about trees?
  • List some questions you have about trees.
  • What could you do to find answers to these questions?

Teaching Tips & Background Information

This question may seem really basic, but in some ways it is the hardest one in this unit to answer. One reason for this may be that the question is so open-ended. The other questions in Unit One will help to focus the discussion, but for now it is okay for students to think broadly.

This is an introductory activity. Thus, its main purpose is to get students interested in, and thinking about, the subject matter. The goal does not necessarily have to be for students to develop a concrete definition of a tree, though this may also be one of the objectives.

You may ask students to write in their journals about these questions and then share their ideas with the class. Or, you could start with a class discussion. Whatever you do, consider keeping track (or having students keep track) of their questions and comments.

This activity provides an opportunity for students and teachers to discover and contemplate what they know and do not know about trees. The questions and answers generated here may provide the motivation for future investigations and also help structure the following lessons. These comments may give insight into which sections of the unit you want to skip over or give special attention to.

Some of the questions brought up in this class discussion will invariably be different than the ones listed in this teachers' guide. Though the questions in this guide highlight some interesting and important concepts, the student-generated questions will also offer learning opportunities in terms of inquiry skills and scientific concepts. Pursuing their own questions can also increase the students' motivation and senses of ownership and accomplishment.

After a list of questions has been collected and students have discussed techniques for answering these questions, such as researching in books or on the internet, asking an expert, and conducting an experiment, you may suggest that the students divide the questions into groups based on subject matter, how they could be investigated or importance to the class. Next each student, or group of students, could choose a topic to investigate outside of class and report back on during a later class period. These reports could range from a few sentences of explanation to a paper, depending on the teacher's goals. You may want to encourage or discourage the pursuit certain questions, based on their ability to be investigated in the amount of time given for the assignment.

It may be interesting to ask the question "What is a tree?" again after students have investigated some of the other topics to see if and how their ideas have changed.
How does a tree make wood?
Materials: A piece of a tree (i.e. a cross section of a truck (known as a "tree cookie"), a branch, or a piece of lumber)
Goals
Other Questions
Students will be able to summarize a conceptual understanding of the process of photosynthesis, including its inputs (H2O and CO2) and outputs (glucose), and explain that this means that wood is made from carbon dioxide and water.Students will be able to define the terms - Photosynthesis- Chlorophyll- Glucose (C6H1206)
  • What raw materials did the tree use to make this piece of wood?
  • Do you think it would be possible for a tree to make this out of CO2 and water?
  • What does a tree turn into when it is burned?
  • What do trees use to as food?
  • Why compound makes leaves green?
  • What does chlorophyll do?
  • Where does the CO2 that leaves take in go?
  • What do trees do with the glucose that they make?

Teaching Tips & Background Information

This question may seem really basic, but in some ways it is the hardest one in this unit to answer. One reason for this may be that the question is so open-ended. The other questions in Unit One will help to focus the discussion, but for now it is okay for students to think broadly.

This is an introductory activity. Thus, its main purpose is to get students interested in, and thinking about, the subject matter. The goal does not necessarily have to be for students to develop a concrete definition of a tree, though this may also be one of the objectives.

You may ask students to write in their journals about these questions and then share their ideas with the class. Or, you could start with a class discussion. Whatever you do, consider keeping track (or having students keep track) of their questions and comments.

This activity provides an opportunity for students and teachers to discover and contemplate what they know and do not know about trees. The questions and answers generated here may provide the motivation for future investigations and also help structure the following lessons. These comments may give insight into which sections of the unit you want to skip over or give special attention to.

Some of the questions brought up in this class discussion will invariably be different than the ones listed in this teachers' guide. Though the questions in this guide highlight some interesting and important concepts, the student-generated questions will also offer learning opportunities in terms of inquiry skills and scientific concepts. Pursuing their own questions can also increase the students' motivation and senses of ownership and accomplishment.

After a list of questions has been collected and students have discussed techniques for answering these questions, such as researching in books or on the internet, asking an expert, and conducting an experiment, you may suggest that the students divide the questions into groups based on subject matter, how they could be investigated or importance to the class. Next each student, or group of students, could choose a topic to investigate outside of class and report back on during a later class period. These reports could range from a few sentences of explanation to a paper, depending on the teacher's goals. You may want to encourage or discourage the pursuit certain questions, based on their ability to be investigated in the amount of time given for the assignment.

It may be interesting to ask the question "What is a tree?" again after students have investigated some of the other topics to see if and how their ideas have changed.
If wood is made of sugar why can't we eat it?
Goals
Other Questions
  • Students will be able to form hypotheses to explain why some organisms can eat and digest wood, but humans cannot.
  • Students will be able to describe the products of photosynthesis (cellulose and starch) with more detail than after the previous discussion
  • Students will be able to discuss the impact of molecular structure on the digestibility of cellulose and starch.
  • What is the difference between plant matter that we can eat and plant matter that we cannot?
  • What is a potato made of? What is bread made of?
  • Why can we eat and digest a potato and a piece of bread but not a tree trunk?
  • Can anything eat and digest wood?
  • What makes an organism able to eat and get nourishment from wood?

Teaching Tips & Background Information

The discussion following this question may take many shapes. Some students may bring up the mechanical side of eating by suggesting, for example, that we do not have strong enough teeth. This is true. Other animals, such as Beavers have large and strong teeth, which they use to chew on trees (mainly the young twigs and new growth).

Other students may point to the digestive side of eating, by suggesting that we cannot digest wood. This is also true. Potatoes are made of starch, which we can digest because we have the enzyme amylase to break it down. Wood is made of cellulose, but we cannot digest it because we do not have the proper enzyme, cellulase, to break it down. Fungi and some protozoa do have this enzyme, which makes them capable of digesting wood (and they do not even have teeth!)

Beavers themselves do not produce cellulase. It is true that their teeth enable them to take the wood into their bodies, but once it is there the digestion of it depends on protozoa that live in the beavers' stomachs.

Both cellulose and starch are made of chains of the same subunit: glucose, but they are bonded together differently, and this difference in structure is what gives the molecules their unique characteristics.

Even though our bodies cannot break it down (actually, because we cannot break it down), it is good for us to ingest some cellulose. The dietary fiber listed on nutrition information panels is none other than this molecule!

Extension Activity
Materials: A loaf of white bread, Popsicle sticks (1 for each student)
Give each student a small piece of bread. Ask them to make predictions (or describe from past experience) how it tastes, and predictions what will happen to it if they hold the bread in their mouths but do not chew it. Ask them to try out the experiment and describe what happens. (They should feel it dissolve and then turn sweet due to the breaking of the starch molecules.) Ask them to go through the same process (including predictions) with the Popsicle sticks and compare and contrast the results.

Other than air, water, and light, what else do trees need?
Goals
Other Questions
  • Students will be able to list the factors, such as light, climate and soil characteristics, which affect tree growth and forest composition.
  • Students will be able to discuss the fact that different species of trees have different requirements in terms of these factors
  • What do roots take in besides water?
  • Can a palm tree survive outdoors in Massachusetts? (Why not?)
  • Are the tree species that grow in a swamp different than the species that grow in dry soil? What is different about these species

Teaching Tips & Background Information

Some of these factors may have been mentioned in the discussion of how trees make wood, but it may be good to discuss them again so that students know that even though wood is made primarily out of carbon dioxide and water, the tree also needs other things in order to live.

The effects and connections introduced here will come up again when students use the SimForest software. The software allows students to change the site properties, which include soil depth, soil texture, soil fertility, average monthly temperature, and average monthly rainfall. Introducing these factors now may help students to use them more effectively later on.

How old is a tree's trunk?
Goals
Other Questions
  • Students will be able to explain that:
    • a) Tree growth occurs in the outer layer of the trunk (the cambium) just under the bark.
    • b) The living part of a tree is on the circumference of the trunk (beneath the bark).
    • c) The inner wood in a trunk (the heartwood) and the bark is dead.

  • Students will also be able to describe the implications of the above information:
    • 1) In a 200 year old tree the only part of the trunk that is 200 years old is located at the center of the heartwood, and this part has been dead for around 195 years!
    • 2) The living part of the tree is no more than 5 years old!
  • Is the whole trunk that old?
  • If not, which part of the trunk is the oldest?
  • As a tree gets bigger where does the growth occur? (In that case which is the oldest part?)
  • The very center of a tree trunk is called the heartwood. Our hearts help to circulate blood and nutrients through our body. What function does a tree's heartwood serve?
  • What does it mean to be alive?
  • Are there parts of our bodies that are dead (hair, nails outer skin)?
  • Is a tree's heartwood alive?
  • Is the bark alive?
  • Which part of the trunk is alive?
  • How old is this part?
  • How old was the oldest part of the tree when it died?
  • Which is more damaging to a tree: boring a hole all the way through it or making a small cut all the way around the circumference?

Teaching Tips & Background Information

Some common misconceptions are that the whole tree trunk is alive, that the heartwood contains the vascular tissues that transport nutrients and water, that the outside of a tree is dead while the inside is alive and that growth occurs throughout the stem.

In reality the cells on the inside of a tree are dead and the outside cells are alive. Not only does the circumference of the trunk contain the growing tissue of the trunk (the cambium), it is also where all the functioning vascular tissues (xylem and phloem) are located. Cambium and phloem cells are constantly sloughed off and replaced, but xylem cells can live for at most about 5 years.

In a discussion format, the teacher may have to tell students some of the information in this lesson, such as that the inside of the tree is dead. Students may be able to construct some of the concepts themselves.For example, talking about tree rings and why trees have them may help students to think about where trunk growth occurs.

Once students have constructed the concepts, or had the concepts explained to them, they should be able to discover the implications for themselves. The last 3 or 4 questions in the other question list are meant to help students realize these implications.

Another way to lead this activity is to have the students answer the questions in their journals (complete with explanations of their answers) before giving them any hints or information. For homework, ask the students to do book or internet research on the questions and write new answers if they would like (but keep the old ones).In the following class students could discuss their first hypotheses, where they looked for answers, and what they found out through their research, thereby dispelling their own misconceptions and teaching each other.
Extension: If you nail a bird hoes 5 feet up in a young tree, how high will it be in 50 years?
Goals
Other Questions
  • Students will be able to use their problem solving skills to solve a riddle.
  • Students will be able to explain that growth upwards occurs at the top of the trunk, not the middle or bottom of the stem.
  • How could you investigate this question without waiting 50 years?
  • Think about other things you have seen attached to a tree like a swing or a sign. In your experience have they moved up over time?

Teaching Tips & Background Information

A common misconception is that a tree's upward growth occurs at the bottom of, or all throughout, the trunk.

In reality, all lengthening of the trunk and branches occurs only on the tips of twigs where the meristematic, (e.g. growing) region is located.

Instead of just explaining this concept to the students try to help them draw on their previous experiences and knowledge in order to figure this concept out for themselves. If they do not understand it right away, this riddle could be left for students to think about over the course of their work with this teacher's guide.

Later, when the class goes on walks in the woods you may want to point out examples of things which have been attached to trees for a number of years, such as barbed wire, signs, or even carvings in the bark, and ask if students think these things have moved up over time.
How much does a tree grow in a year?

Materials

  • Tree cookies, tree cores, or tree stumps with clear rings
  • Graph paper
  • Pencils
  • Rulers
Goals
Other Questions
  • Students will be able to make graphs, known as dendrograms, to illustrate the growth of a tree's radius over time, and how the growth rate varied from year to year.
  • Students will be able to explain why
    • a) Trees in colder climates have rings. (The growing season varies throughout the year. Cells that are born in spring are larger and lighter in color than the ones that are born in summer and autumn, and in winter cells are not born at all.)
    • b) Trees in regions with a less varied climate do not have rings.
    • c) A tree's rings vary in size based on growing conditions.
  • What does a tree ring indicate?
  • What can you learn from a tree ring?
  • Why do trees in New England have rings?
  • Do trees in warmer climates have them? (Why not?)
  • Why are the different rings different sizes?
  • What factors might affect how a tree grows?
  • What tools and process could you use to make a graph of a tree's radius over time?
  • What if you wanted to graph the growth rate of a tree over time?
  • What would the X and Y-axes stand for?
  • What would the units be?

Teaching Tips & Background Information

Concrete evidence of how trees grow by adding to the circumference of their trunk each year can be seen in a tree's rings. Tree rings also illustrate the effects of climate on tree growth. Thus, an examination of tree rings may help to reinforce both these concepts.

It is relatively easy to make a graph of a tree's radius (distance from the center to the outside ring) over time. Students can make them using a tree stump, cookie or core, graph paper and a pencil.

Making this type of Dendrogram does not even require that you make any measurements because the tree rings themselves can serve as the ruler.

Method
Begin by drawing and labeling the X and Y-axis. Each square on the X-axis stands for a year and the Y-axis measures the radius of the tree (actual size). Next, line the center of the tree up with the origin of the graph so that the rings are perpendicular with the Y-axis. Keep the center of the tree on the X-axis (Y=0) and the rings perpendicular to the Y-axis at all times during this activity. Make a dot where X=1 (year one) and the radius after year one (the width of the first ring measured on the Y axis) intersect. Make a dot where X=2 (year two) and the radius of the tree after 2 years (the width of the first 2 rings measured on the Y axis) intersect. Continue with year 3, 4 etc. until you get to the bark of the tree. By connecting all of the dots you get a growth curve for the tree! (See figure). To make it easier to see the rings while they are graphing, students can first mark off each ring on a piece of paper and then use the paper, instead of the rings themselves, to measure the radius on the graph.If the year that the tree was cut is known, students can also label the years on the X-axis by counting back from this year.A Partial Graph of Tree Radius against Time Made Using a Tree Core, (Reproduced to the Right)

Students can also create a graph of growth rate over time by graphing the width (in mm) of each ring against time in years.

At some point, either before or after making graphs, it may be interesting to lead student in a discussion about why trees have rings, and what the rings tell us about the trees and their environment.

Extension: How much length does a branch gain in a year?

Materials

  • Tree branches with clear terminal bud scars
Goals
Sub Questions
  • Students will be able to determine how much a tree's branch grew in a year by measuring between the terminal bud scars.
  • Where does growth occur on a branch?
  • How could you measure how much a twig grows in a year?

Teaching Tips & Background Information

Because the lengthening of tree branches occurs at the terminal bud students can also determine how much a tree branch lengthened in a year by measuring the distance between the terminal bud scars

Why do trees lose their leaves?
Goals
Other Questions
  • Students will be able to form and discuss hypotheses about
    • a) Why trees lose their leaves before winter.
    • b) What triggers leaves to fall.
    • c) How conifers have adapted to the challenges of winter without losing their leaves.
  • Students will be able to describe how trees lose their leaves through an active process of abscission and explain a theory of why some trees, such as red oaks, hold on to their leaves after they have turned brown.
  • What is the purpose of leaves?
  • Why do they fall off in the autumn?
  • What makes them fall?
  • What triggers a tree to lose its leaves? (How would you study this?)
  • Why do the leaves of some trees, like red oaks, turn brown but not fall off?
  • Do conifers have leaves?
  • How have evergreen trees adapted to the issues of winter without losing their leaves?
  • What are the advantages of keeping leaves over the winter?
  • What are the disadvantages?

Teaching Tips & Background Information

Most of the above questions have a number of possible explanations. Thus you may want to ask students to generate multiple hypotheses for each question.

Some hypotheses for why trees lose their leaves that were generated in a model class were:

  • To conserve water and energy.
  • To collect less snow (and prevent breakage due to weight)
  • Because there is less sun and therefore less possibility to photosynthesize
  • To shed parasites.
    All of these may be benefits of shedding leaves.

A common misconception is that trees lose their leaves because an outside force, such as wind or rain knocks them off.

In reality, trees actively form an abscission layer, or layer of cells that separates the leaf from the branch, and when this layer is complete the leaf falls.

Some hypotheses about what triggers leaves to fall were:

  • Day length
  • Sun angle
  • Temperature

Scientists have done research on this subject and found that day length (or more correctly night length) appears to be the main trigger. Leaves contain a chemical called phytochrome, which exists in two forms. It changes into one in the light and decays into the other in the dark. Based on how much of the first form is left in the morning, the leaves "know" how long the night was, and at a certain night length (this can be individual for each tree or species) the tree begins to form the abscission layer.

In New England, red oaks are at the northern end of their range. Down south, their leaves do fall, but here the temperature becomes too cold (and the cells stop growing) before the abscission layer is complete.

Other trees, such as pines and hemlocks, keep their leaves over the winter. In order to survive the difficulties of this season they have developed other adaptations, such as waxy leaves and slender needles.

Brainstorming on this topic may help students think about the various adaptations that can develop in response to the same environmental condition.
Extension: Do conifers ever lose their needles?

Materials

  • Pine boughs with needles attached
Goals
Other Questions
  • Students will be able to determine how old a pine needle is by counting the whorls.
  • How old can a pine needle get before it falls off?
  • How would you figure this out?

Teaching Tips & Background Information

The most recent pine needles are the ones closest to the tip of the branch; the oldest are the ones furthest down the branch. To determine the age of a whorl (and therefore its needles) count back from the most recent whorl. You may want to compare bows from more than one tree.

This branch was collected in the spring before any of this year's needles had grown. That means that the needles on the most recent whorl are almost one year old, and the needles on the second whorl are almost two years old. The needles from 3 years ago have already fallen off.
How can you tell trees apart?

Materials
A tree branch that will be readily identifiable by students.

(In the summer, maple or oak with leaves or a pine branch will do. In the winter an oak with clinging leaves, or a white pine bow serve nicely. White pine is especially useful in either season because it can be easily identified to the species level, while it can be more difficult to distinguish between the different types of oaks or maples even when their leaves are intact.)
Goals
Other Questions
  • Students will be able to distinguish between different parts of a tree.
  • Students will begin to be able to identify trees based on their characteristics.
  • What kind of tree is this?
  • How do you know?
  • What are the distinguishing characteristics of a tree?

Teaching Tips & Background Information

A list of tree characteristics generated in a sample class looked like this:

  • Form
    • Branching pattern
      • Alternate for oaks, beech etc.
      • Opposite for ash and maple
      • Whorled for conifers
    • Shape
    • Size
  • Leaves (remember needles are leaves too!)
    • Shape
    • Number
    • Size
    • Color
  • Bark (changes with age)
    • Pattern and texture
    • Color
  • Buds (useful in spring and winter)
  • Flowers (You may want to ask a question like "Do trees have flowers? What do they look like?")
    • Gymnosperms (mainly conifers) have naked seeds in cones
    • Angiosperms (mainly deciduous) have covered seeds.
  • Fruit (You may want to ask: "Do trees have fruit?)-
    • Maples - "helicopters"
    • Oaks - acorns
    • Gymnosperms seeds in cones, sometimes berries (Juniper)

The students in your class may not come up with all of these characteristics, but by looking at the tree samples, they will come up with some of them. You can mention some of the characteristics that students leave out, or allow this to be a partial list.

You may also want to bring in a number of branches of different types and ask students to describe them in detail in their journals. You could also bring in a couple branches of the same species and ask students if they are from the same species, and how they know.

Both of these activities may help students to notice the features and characteristics of a tree, as well as the similarities and differences between the different species. These activities may also provide a context in which students are motivated to learn the vocabulary.

Why aren't there trees with Maple-shaped leaves and acorns?
Goals
Other Questions
  • Students will able to define the term species.
  • Why are all these traits (form, leaves, bark, flowers, fruit) so correlated within a type of tree?
  • Can a maple breed with an oak? (Why not?)
  • Aren't their some different species that do interbreed?

Teaching Tips & Background Information

In a sample class the responses that students gave to this topic question were somewhat circular at first. For example, "Maples have certain characteristics and oaks have other characteristics." Comments such as this did not get to the heart of the question, which is, why is there a difference between oaks and maples to begin with?

When we asked students to dig a little deeper, one student responded that they are unique because they are different species and cannot interbreed because they have different pollen receptors and incompatible DNA.

Sometimes the line is a little bit fuzzy. There are examples of species that do interbreed, for example red and black oaks, but in general the rule that an organism can only breed with members of its own species holds true.
Extension: But what's in a name?
Goals
Other Questions
  • Students will be able discuss the politics of species classification.
  • Does it make any difference whether or not an organism is labeled as a distinct species?
  • How might classification affect environmental policy?

Teaching Tips & Background Information

Students may be interested to know that people and organizations interested in protecting endangered wildlife and habitat often work to get unique breeds or communities of animals to be labeled as a separate species because once it has species status it can be placed on the endangered species list and is therefore more likely to be protected. On the other hand, people and corporations that want to use protected resources often want to group more organisms under the same species name.

Sometimes species may go on and off of the endangered species list not because of a change in its numbers, but rather a change in its classification as a species.
Extension: Are trees individuals?
Goals
Other Questions
  • Students will discuss the concept of individuals of a species as it pertains to trees and humans.
  • Look around the room. Are all of us members of the same species?
  • Can you distinguish your classmates from each other?
  • Are trees individuals?
  • Can individual trees be told apart? (Why or why not?)

Teaching Tips & Background Information

These questions are somewhat more philosophical than some of the others and may result an interesting discussion.

Some tree species sprout from the roots, thereby creating clones or trees with the identical genetic make-up.

You may want to ask students if a cloned tree is less of an individual than a tree that is genetically unique. Also, would cloned trees look more similar than trees with different genes? What about the effect of the environment? Are human clones (identical twins) less of individuals than other humans?
Which type of trees grow around here?

Materials
For collecting and labeling twig samples: Pruning shears, Masking tape, Permanent markers
For making bark (and leaf) rubbings: PaperSoft pencils or charcoal
For taking notes: Student journals
Goals
Other Questions
  • Students will be able to list and identify some of the tree species that grow around them.
  • Do you recognize any of these trees? What trees are they?
  • What examples of different types of bark do you see?
  • How about examples of different branching pattern (and buds, leaves, or flowers - depending on season)?

Teaching Tips & Background Information

Identifying trees can seem like a daunting task, but once you know what to look for and have had a little practice it is not so hard. Prior to leading this activity, you may want to get some experience with tree identification and familiarize yourself with the appearance and characteristics of some of the local trees, as this may make it easier for you to help your students.

This activity is meant to introduce students to the steps and techniques of tree identification:

  1. Seeing certain parts.
  2. Knowing the various shapes and sizes of these parts.
  3. Assembling suites of these parts.
  4. Knowing the "tricks" and obvious trees.

You may want to start this class with a discussion in which you and the students agree on goals and methods for the walk.

Review the tree characteristics, but this time be more specific about what each feature means and connect the characteristics with species.

For example, it will be helpful for students to know exactly what is meant by opposite and alternate branching pattern, as well as the fact that maples and ashes are the only species New England forests to exhibit opposite branching pattern. Thus, if a tree has opposite branches, it is either an ash or a maple. Ashes can be distinguished by their rough, "diamond pattered" bark, and you can sometimes also tell maples apart by their bark (red maples generally have rougher bark than sugar maples).

Some species are especially easy to identify. These include beech, yellow birch, and black birch. (Distinguishing between paper and gray birch can be more difficult.)

You might suggest that students take notes in their journal or notebook about tree identification tips and "what to look for" so that they can refer to them during the walk.

On the walk, ask students to take note of interesting bark patterns and color, branching pattern, leaves, buds etc.

Students can take rubbings of bark with interesting texture, and clippings of interesting twigs. It may be useful for students to label the samples they collect. If you know the name of a tree that students are sampling you may want to tell them, but students can also guess the species name and include some other characteristics of the tree.

Students will be able to use the samples with known species names as references later, and it they want to use a guidebook to identify the unknown samples, having a hypothesis and list of descriptions may prove very useful.
Unit Two: Trees in the forest
The main purpose of this unit is to get students into the woods and asking questions of the trees themselves by surveying a plot. The activities found here expand on the previous unit by bringing the concepts into their real world application: the forest. These activities also provide students a true context for their subsequent work with SimForest by giving students an idea of the size of a 10 x 10 meter plot, as well as the number and types of trees that might be found on such an area. In our trials of the software we found that students who had spent class time surveying a forest plot before beginning work with SimForest were more effective at using the software and appeared to get more out of the simulation than students who had not had such an experience.
Though this unit is broken into just 2 activities, students could spend weeks investigating them. Because surveying a plot is an active, hands-on activity, it may help to draw students more deeply into their study of trees and forests. For this reason you may choose to begin this activity early on in their investigations of trees, before they have finished their work in unit one. Students may also continue to work on surveys after they have started investigating the questions in Unit Three. One way to structure your classes would be for students to spend one or two days a week outdoors surveying plots and the rest of the week in the classroom engaged in investigations from Units One and Three.
The structure of Unit Two is more linear than Unit One: Students should understand how a trees size is measured before they go into the field and they must survey a plot before they can map it. However, this unit could be shortened or expanded. In the barest version, students would simply identify (and record) every tree on plot. A more in depth investigation would include measuring and recording each tree's diameter at breast height (DBH) as well. In the most advance version of the unit, students would also map the location of the trees on the plot. Students could also survey more than one plot, in order to compare different plots with different compositions and characteristics.
How do you measure the size of a tree?
Goals
Other Questions
  • Students will be able to measure a tree's circumference at breast height.
  • Students will be able to convert circumference at breast height to diameter at breast height (DBH), which is a standard measurement of tree size.
  • One standard way that foresters estimate the size of a tree is by measuring its diameter at breast height (DBH). How would you measure DBH?
  • What if the tree is not round?
  • Why do foresters measure trees at breast height?

Teaching Tips & Background Information

One way to begin is by asking your students to brainstorm ways of measuring a tree, and then introduce them to the standard measurement of forestry: diameter at breast height (DBH), and ask them to brainstorm how they would take that measurement.

In our region, tree trunks are flared at the bottom, but have pretty much straightened out by about 3 to 4 feet up; Thus breast height a good place to measure. However, such a standard would not work so well in the tropics where trees have much larger and taller buttresses.

You may want to introduce students to the method of measuring DBH in the classroom so that they will have strategies planned once they get into the woods.

One way to measure DBH is to hold a yardstick up the trunk so that it is parallel to the ground and read off how wide the trunk is. However, if the tree is not round this method can be inaccurate.

A more accurate method is to measure the circumference and then convert it to diameter.
Remember: C = pi*D (Circumference = pi times Diameter), and therefore D =C/pi
There are actually DBH measuring tapes that do this conversion for you by measuring in cm/pi or in/pi, which makes it possible to wrap the tape around the circumference of the trunk and read off the diameter.
How do you map a plot?
Materials:
In the plot: Measuring tape, Clip boards with graph paper (for recording data), Pencils, Compass, Flags and/or marking tape (to mark edges of plot and measured trees),Yard sticks (if you want to measure tree height)
In the classroom: Rulers, Pencils, Graph paper, Protractors
Goals
  • Students will be able to
    • Identify trees
    • Measure trees and distances
    • Map a plot

Teaching Tips & Background Information

Depending on the size of your class you may want to divide the students into teams to survey one or more plot(s).

You may want to begin by having students use the measuring tape to map out the edges of the plot. In SimForest, the plot is 10 meters by 10 meters. Surveying an actual plot this size may give students some context for interpreting the model.

If you and your students have decided to only record the species or species and diameter for each tree do that now.

If you have decided to map the plot, start with a center point and then measure a tree's distance and compass bearing from that point (See Figure)

Set up the data table for this type of plot like this:

Tree ID # Species DBH Distance from Center Compass Bearing 1 Hemlock 10cm 3.2 m 45o

To turn this table into a map, begin by deciding on a scale and marking out the borders of the plot on the graph paper. Next, draw in the center point and an arrow pointing north. Using the protractor, measure the bearing of the first tree from north on the map and the ruler and scale to mark out the distance of the tree from the center along that bearing. Repeat this for all of the trees in your plot. You may also want to draw the tree trunks to scale and use a color key to indicate their species.

Extension: What is the soil in your plot like?
Materials:
Garden shovels
Goals
Other Questions
  • Students will describe the texture of the soil in their plot using qualitative observations.
  • What does the soil feel like?
  • Would you describe it as sand, silt, clay, something else or a combination? If is a combination, how much of each component do you think the soil contains?

Teaching Tips & Background Information

A very quick and easy way to get an idea of the soil texture of your plot is to dig a hole about 2 feet deep and feel the soil inside with your hands.

Ask students to make qualitative observations of the soil (color, texture etc.) and make an educated guess about where the soil falls on the sand - clay continuum.

Grainy = Sand
Fine = Silt
Very Fine (and often wet and pasty) = Clay.

Tell students to record their observations in their journals.

The SimForest program allows users to set soil texture, so this information may prove useful later on.
Unit Three: Forest Growth & Change
This unit is meant to scaffold students' investigations with the SimForest software. Throughout their work with this tool, you may want to have students work at the computers in teams of 2 to 4 students (I will henceforth refer to these as computer teams. The first time that students open the software they will have a lot to take in terms of visual displays and variables that they can manipulate. They will need time, sometimes an entire class period, to play around with these features and variables without having to stick to a ridged experiment or technique. At the same time, it may also be difficult for them to learn how to use the software without guidance for an introductory activity that may help lead students through using some of the features. Do not worry about introducing students to all aspects of the software on the first day because once they get the idea most students will explore on their own or ask questions about the different features as the need for them arises.
After students have been introduced to the model, you may want to review the questions that they have generated during their work in Units One and Two to see if any of these questions could be examined using SimForest. Students should also brainstorm new lists of questions to investigate using the simulation. Subsequent investigations can involve both the questions students ask and the ones presented in this model.
Most of the heading questions in this unit will easily take up an entire class period or even longer, though some, such as, "Does the simulation always yield the same results?" may take up less time and could even be included as part of one of the other beginning activities. In the first few activities (leading up to and including "Can we simulate the plot we surveyed?"" all of the questions listed under each heading could be explored together as part of the same investigation.
However, in later activities (from "How does temperature affect forest composition?" through "How do 'natural disturbances' affect forests"), though the questions included under each heading involve similar themes, many could be the center of their own investigations. We do not expect that students will investigate every question in a given category. Rather that they will choose the one(s) that interest them most and/or explore questions that they have come up with themselves. You may want to encourage a few computer teams to investigate the same, or similar, questions so that they will be able to compare hypothesis, methods, results and conclusions.
Using SimForest: Helpful Features & Information
Students may find the following information useful in their work with SimForest. However, these features are not meant to be the focus of a lesson. They are listed here to give teachers an idea of some of the different aspects of the software so that they will be able to introduce students to these tools and explanations as a need for them arises. This information is also meant to help teachers explain units, terms, and abbreviations that might be confusing and unfamiliar.
Features
Overhead Scroll Over
By scrolling over the trees in overhead view you can gain useful information including
Height (Hgt)
Diameter (Dmr)
Species
Age
Site Quality (SQ) A number between 0 and 1 that quantifies the suitability (in terms of soil nutrients, water, and temperature) of a site for that species of tree. The higher the number the more suitable the conditions.
Light Factor (LF) A number between 0 and 1.45. It is calculated from the shading leaf weight (number and type of trees growing above the tree in question), and the light response of the species (shade tolerant, intolerant, or intermediate) The larger the number the more suitable the light conditions are for the scrolled tree.
Growth Rate (dD) * You can also get some (but not all) of this information by scrolling over trees in the orthogonal view.
Tree Inspector
By clicking on a tree once in the overhead or orthogonal view, you will bring up the tree inspector. In the tree inspector you can-
Change the species, age, diameter, and location of the tree you clicked on.-
Remove the tree from the plot
Saving Functions
The Save Snapshot button allows you to save the current state of the simulation and the current settings of the properties and seed pool.

The Load Snapshot button allows you to open a snapshot in SimForest that you have already saved.

The Export Plot History button allows you to save all of the tree data (species, number of stems, DBH etc.) that have been generated by the simulation since the last resetting of the plot. This cannot be opened again in SimForest, but it can be opened using the forest analysis tools. These tools help you graph the data using excel.
Seed Pool, Nursery, and Manager
In the Manager you can -
Reset the plot (i.e. return to an empty plot). This feature does not reset any changes you have made to the seed pool or properties windows-
Turn recruitment on and off. "When Recruit On?" is checked, new trees can come on to the plot, when it is not checked, no new trees can seed in.- View graphs of available light and number of trees vs. height.
In the Seed Pool you can-
View a list of species for which the model has equations.-
Remove a tree from the seed pool (prevent it from growing) by clicking on it and turning it red. (To restore a species to the seed pool click on it again to turn it black.)
In the Nursery you can-
View a list of species for which the model has equations.-
Select a species to plant by clicking on it. (This only works if the species is selected and planted in overhead view.)-
View the maximum height, maximum diameter, and growth rate for the species selected.
Temperature (Properties Window)
The temperature graph displays average monthly temperature in Celsius.You can change the temperature by dragging each month's temperature with the cursor, or by clicking on + and - buttons to move the whole profile up or down. The value that gets plugged into the growth equations can be found in the degree-days box. 365Degree days = S (Td - 7.2 o C) d=1Or, the sum of the daily temperature (Td) minus 7.2 oC (the temperature at which trees stop growing) as d (day) goes from 1 to 365 (1 year).
Rainfall (Properties Window)
The rainfall graph displays average monthly rainfall. You can change this rainfall the same way you change the temperature, by dragging each month's rainfall individually or clicking on the + and - buttons to raise or lower the whole profile.The value that gets plugged into the growth equations is the average yearly rainfall, which can be found in the average rainfall box.
Soil Sliders (Properties Window)
All of the soil sliders can be changed by dragging the slider with the mouse.Soil Fertility is a fertility index measured in units equivalent to grams of nitrogen per hectare (10,000 m2)Soil Texture, measured in mm / mm water, tells how much water can be held by the soil. (e.g. how clayey or sandy the soil is.) A soil texture of 25 is sandy. A texture of 250 clayey.Soil Depth measures the centimeters of soil above the bedrock.
Other Information
Some Simplifications of the Model
Location
A tree's location on the plot does not matter. In the simulation, every tree shades or is shaded by every other tree equally, regardless of their proximity to each other.
Trees and the Environment
In this model the environment (climate, light soil) determine tree growth. Tree growth determines available light but has no impact on climate, water, or nutrients (i.e. roots do not increase the soil's ability to hold water, and nutrients are not lost when trees are cut.)
Equations
Growth Equation
In this equation, the increment of growth is proportional to the diameter of the tree, the growth rate, closeness to the maximum diameter, and the suitability of the site for that tree.
The Growth Equation: dD = G * D * ( Dmax - D) * Lf * Tf * Wf * Sf / Dmax
dD = change in diameter over time
G = optimal growth rate
D = diameter
Dmax = the maximum diameter (based on field observations)
Lf = light factor*
Tf = temperature factor**
Wf = water factor**
Sf = soil nutrient factor**
*Ranges between 0 and 1. 45 where 0 = least favorable and 1.45 = the most favorable. Calculation based on available light and species response.
**Ranges between 0 and 1, where 0= least favorable conditions, and 1= most favorable. Calculation based on site properties and species response.
How do I use the SimForest program?
Goals