![](media/image1.png){width="0.5834645669291338in" height="0.75in"}Life
Science

*Middle School Ecology*

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height="7.227777777777778in"}

# Fire 75

1.  **Fire 101** A lesson/activity designed to introduce students\
    to the fire triangle. 76

2.  **The Tree Ring Mysteries** A lesson that allows students\
    to explore dendrochronology (studying the past by looking at\
    tree rings) and debate controversy over prescribed burns. 79

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Fire

The perception of fire and the influence of the media greatly affect the
National Park Service's (and other agencies') management of the land and
decisions made in the event of wildfire. Fire is the most influential
ecological disturbance of the park's plant and wildlife. Fire has played
a major role in shaping the grasslands that once dominated the park
landscape. Very aggressive wildland fire suppression and extensive
grazing of cattle and other domestic animals have drastically altered
this grassland ecosystem. Grazing and fire suppression have favored the
increased abundance and distribution of shrubs and succulent desert
plants. Therefore, the animal population has changed because of the new
plant community reducing biodiversity in the area.

This unit will focus on the basics of fire and its influence on the
ecosystem. In the first activity, *Fire 101,* students conduct an
in-class lab to learn the three ingredients of fire. In the second
activity, *The Tree Ring Mysteries,* students are introduced to
dendrochronology through the study of tree rings. The activity
encourages students to carefully examine tree rings for evidence of fire
in the tree's past. The students also develop a debate over the
controversial issue of prescribed fire.

![](media/image3.png){width="0.6in" height="0.8346456692913385in"}

**Fire 101**

***What are the ingredients of a fire?***

**Summary:** This lesson is designed to help students understand the
ingredients of a fire and what chemical reactions take place during a
fire.

**Duration:** 1-2 class periods

**Setting:** Lab

**Vocabulary:** combustion, fuel, oxidation, dehydrated

**Standards/Benchmarks Addressed:** SC1-E2, SC2-E1, SC2-E2, SC2-E3,
SC3-E1, SC4-E1, SC4-E2, SC4-E3, SC5-E1, SC5-E2, SC5-E3, SC6-E1, SC6-E2,
SC6-E3, SC6-E4, SC6-E5, SC6-E6, SC9-E1, SC9-E2, SC9-E3, SC12-E1,
SC12-E2, SC14-E1

**Objectives**

Students will:

-   explain the three ingredients of fire and the chemical reaction that
    causes rapid oxidation -- combustion.

**Background**

How do fires begin? In the Chihuahuan Desert, the main cause of fire is
lightning strikes from thunderstorms. No matter what the cause every
fire needs three ingredients---fuel, heat, and oxygen.

***Fuel*:** Fuel is any combustible material. During the long summer
months in the Chihuahuan Desert shrubs and dead grasses provide "dry
fuel" and burn very easily. When years go by with no fire this dead
plant material builds up, so when fire occurs, there is ample fuel to
burn.

***Heat*:** The typical climate of the area includes long, dry summers
with very little rain. These conditions increase the temperature of the
ground and the fuels there, making it easier for the fuel to ignite and
burn. Dry fuel ignites easily from sources such as lightning, a
campfire, a burning cigarette butt, or a match.

***Oxygen*:** Wind is a typical occurrence in nature. The wind not only
increases the oxygen supply and dries out the fuels it also influences
the spread of fire. Shrubs are more quickly ignited when their small
leaves are surrounded by plenty of oxygen.

Fire is a chemical reaction. When combined, the ingredients work
together in this way. Start with a fuel, such as dry shrubs, which
contains hydrogen and carbon atoms. When the summer sun hits the shrub,
it raises the temperature of the shrub, drying it out. When an ignition
source such as lightning contacts the shrub, it breaks the bonds between
the carbon and the hydrogen. This allows them to react with O~2~ in the
air, releasing CO~2~, H~2~O, and heat-oxidation. Oxidation releases
heat, which triggers more bonds, and more heat in a positive feedback
cycle. This is known as combustion (burning).

**Fire Triangle**

The reaction, represented by the fire triangle, shows that fuel, heat,
and oxygen are necessary to create fire. If any one of them is missing,
there can be no fire.

**Materials**

Ingredients of Fire worksheet

Candles set up in aluminum pie pans or tin foil

Matches

Glass jars that fit over the candles

**Procedure**

***Warm up:*** Ask students what a fire needs to burn. What if one of
the ingredients is missing? Do you still have a fire?

***Activity***

1.  Discuss the fire triangle. Tell students that all three
    elements---fuel, heat, and oxygen---are needed for a fire to burn.
    If one is missing there is no way that a fire can burn.

2.  Divide the class into small groups and pass out the materials needed
    for the lab.

3.  Light the candle.

4.  Have the students observe the burning candle for three to five
    minutes. They must answer questions 1-5 on the Ingredients of Fire
    worksheet.

5.  Students now place the glass jar over the burning candle until it
    rests on the table. Students observe the reaction and answer
    questions 6-7.

6.  Have the students research the answers to sections B and C on the
    Ingredients of Fire worksheet.

***Wrap Up:*** Have the students present their answers and discuss as a
class.

**Assessment**

Lab worksheet

**Extensions**

Have students draw the fire triangle and label the parts.

**Ingredients of a Fire**

**Name: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_**

A. Observe the burning candle.

1.  What is the source of fuel?

2.  What is the source of heat?

3.  What is the source of oxygen?

4.  What is the evidence of oxidation?

5.  What color represents the hottest area of the flame?

6.  What happened when you eliminated one of the three ingredients of
    fire? Why?

7.  Explain the chemical reaction that took place:

B. Why are more fires likely to burn during hot weather than during cool
weather?

C. Why would plants with smaller leaf surfaces burn faster than those
with larger leaf surfaces?

![](media/image3.png){width="0.6in" height="0.8346456692913385in"}

**Tree Ring Mysteries**

***What can you learn from a tree?***

**Summary:** This lesson is designed to help students understand what
events have happened in an area using dendrochronology.

**Duration:** 1 week

**Setting:** Classroom/lab

**Vocabulary:** dendrochronology, wildfire, prescribed fire,
prescriptions

**Standards/Benchmarks Addressed:** SC1-E1, SC2-E1, SC3-E1, SC4-E1,
SC4-E3, SC4-E5, SC5-E2, SC6-E1, SC6-E2, SC6-E3, SC6-E4, SC6-E5, SC6-E6,
SC6-E7, SC6-E8, SC11-E6, SC12-E2, SC14-E2, SC14-E3, SC15-E2, SC16-E1,
SC16-E2, SC16-E3

**Objectives**

Students will:

-   explain how scientists use dendrochronology.

-   understand the importance of tree rings.

-   examine tree rings for age and significant events that have affected
    the tree's growth (fire, drought, etc.)

-   debate the controversial issue of prescribed fires.

**Background**

The major cause of wildland fires in Carlsbad Caverns National Park is
lightning strikes during summer thunderstorms. These prairie and
woodland fires are well documented in historical records. Tree ring
studies have documented fire scars hundreds of years back. The science
of studying the past by looking at tree rings is called
dendrochronology. Scientists can learn a great deal from studying tree
rings. For example, they can learn how old a tree is, when a fire
occurred in the area, and they can also learn about the climate of an
area.

Fire is the most influential ecological disturbance of the park's plant
and wildlife. Fire has played a major role in shaping the grasslands
that once dominated the park landscape. Very aggressive wildland fire
suppression and extensive grazing of cattle and other domestic animals
have drastically altered this grassland ecosystem. Grazing and fire
suppression have favored the increased abundance and distribution of
shrubs and succulent desert plants. Therefore, the animal population has
changed because of the new plant community reducing biodiversity in the
area.

Prescribed fire is an essential tool to restore this out-of-balance
ecosystem. First, some of the naturally ignited (lightning) fires are
allowed to burn when certain predefined conditions (prescriptions) of
wind speed and direction, relative humidity, and fuel moisture are met.
Second, prescribed (controlled) fires are ignited at planned locations
by trained fire personnel. These prescribed fires are conducted under
controlled conditions and monitored by professional fire teams.

By studying a tree trunk, scientists can determine more than a tree's
age. They can also learn about the weather in past years from its
effects on the tree. Annual rings vary in width. Growth is much slower
during periods of drought. A lack of water causes an annual ring to be
narrow. A year in which the temperatures are warmer than usual can have
a long growing season. A longer growing season would provide a wider
annual ring.

Below is a labeled tree ring.

![](media/image4.png){width="5.017361111111111in"
height="3.2256944444444446in"}

**Materials**

Tree Ring handout

Sample tree rings with evidence of a variety of events (fire, drought,
etc...)

Lab worksheet (teacher created based on tree rings obtained)

**Procedure**

***Warm up:*** Ask students what they can learn from a tree. Write
responses on the board and discuss. Pass out Reading Rings worksheet.
Have students match the event on the right with a sample tree ring on
the left. The tree rings can be used more than once. Discuss the
background information for this lesson.

***Activity***

1.  Hand out the Tree Ring Handout. Have the students cut out the core
    samples at the bottom. Be sure they leave the letter on the core
    sample so they know which sample they are using.

2.  Have the students decide which core sample matches the tree ring
    sample. They do this by laying the core sample across the tree ring
    looking for a matching pattern of lines. (Be sure that the students
    understand that core samples do not go father than the core of the
    tree, so the core sample should not cross the center of the tree.)
    Ask students which core sample is the one that matches the tree
    ring.

3.  Have the students observe the tree ring handout. Then have them
    assign dates to the important events in the tree's life. What year
    did fire scar the tree? (1915) How many years did it take the tree
    to grow around the remains of a dead branch? (10 years) How long did
    the drought that began in 1912 last? (2 years).

4.  Hand out lab worksheet (teacher created). Have the students observe
    the tree rings arranged around the room and complete the lab
    questions (teacher created). Teacher may need to contact their local
    Extension Agent, National Park, or local Forestry official for the
    tree ring samples.

5.  Discuss the need for fire in an ecosystem and how it brings balance
    to an unhealthy ecosystem. Discuss the need for prescribed fire.

***Wrap Up -- Debate***

Survey the students' feelings on prescribed burns in the National Parks.
Have each student research and prepare a debate on the opposite view
than they possess (Try to divide the class as evenly as possible- some
students may have to write on their own view to keep things even). If
the student supports prescribed burns they take the stance against
prescribed burns. If the student is against prescribed burns they take
the stance for prescribed burns.

Give the students several days to work on the research for their portion
of the debate project. Divide the class into debate groups of 4-6 (2 to
3 students from each side). Have each group debate the issue to the
whole class.

**Assessment**

Rubric for debate

**Extensions**

Take the students on a field trip to a local watershed, for instance,
Smith Springs, in Guadalupe Mountains National Park. Have the students
look for signs of a fire in the area's past. Have them write down any
evidence they find that indicates that a fire has burned in the area.

Ask a firefighter from the local National Park to come to class and
discuss the effects of wildfire and prescribed fire in the National
Parks. Some questions they should cover include: Are all wildfires bad?
Do they let some wildfires burn? Why or why not? What is a prescribed
fire? Why do they have prescribed fires? What considerations do they
have to look at before, during, and after a prescribed fire?

Tree Ring Handout

**Directions:** Cut out the core samples labeled A-C at the bottom of
this page. Be sure that you do not cut off the letter or dates on the
core samples. Match the core sample to the tree ring sample by laying
the core sample across the tree ring sample. Be sure that the core
sample does not go further than the core of the tree.

![](media/image5.png){width="6.500694444444444in" height="7.5in"}

Worksheet adapted from: Ranger Rick's Nature Scope: Trees are Terrific!

**Reading Rings Worksheet**

**Name: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_**

**Directions:** Carefully observe the rings on this worksheet and match
them to the events on the opposite side. The rings may be used for more
than one event.

![](media/image6.png){width="5.996527777777778in"
height="7.274305555555555in"}

Worksheet adapted from: Ranger Rick's Nature Scope: Trees are Terrific!

Prescribed Fire

+---------------------------------+-----------+------------+-----------+
| # Debate                        | **Self    | **Teacher  | **C       |
|                                 | eva       | ev         | omments** |
|                                 | luation** | aluation** |           |
+---------------------------------+-----------+------------+-----------+
| **Information:**                |           | **/12**    |           |
+---------------------------------+-----------+------------+-----------+
| Includes detailed factual       |           |            |           |
| information                     |           |            |           |
+---------------------------------+-----------+------------+-----------+
| Supports the assigned viewpoint |           |            |           |
+---------------------------------+-----------+------------+-----------+
| Shows evidence of preparing for |           |            |           |
| the opposing side's arguments   |           |            |           |
+---------------------------------+-----------+------------+-----------+
| **Presentation:**               |           | **/16**    |           |
+---------------------------------+-----------+------------+-----------+
| Stays calm during the debate    |           |            |           |
+---------------------------------+-----------+------------+-----------+
| States argument clearly so      |           |            |           |
| people understand what is being |           |            |           |
| said                            |           |            |           |
+---------------------------------+-----------+------------+-----------+
| Shows eye contact with the      |           |            |           |
| other speaker and audience      |           |            |           |
+---------------------------------+-----------+------------+-----------+
| Speaks clearly and loudly so    |           | **/4**     |           |
| audience can hear               |           |            |           |
+---------------------------------+-----------+------------+-----------+
| **Teamwork:**                   |           |            |           |
+---------------------------------+-----------+------------+-----------+
| Are the efforts of each team    |           |            |           |
| member clearly demonstrated, or |           |            |           |
| did it appear to be the work of |           |            |           |
| one or two?                     |           |            |           |
+---------------------------------+-----------+------------+-----------+
| **Overall:**                    |           | **/12**    |           |
+---------------------------------+-----------+------------+-----------+
| Has the student fulfilled all   |           |            |           |
| the parts of the task?          |           |            |           |
+---------------------------------+-----------+------------+-----------+
| Has the student used proper     |           |            |           |
| grammar and sentence structure? |           |            |           |
+---------------------------------+-----------+------------+-----------+
| Has the student cited           |           |            |           |
| appropriate resources?          |           |            |           |
+---------------------------------+-----------+------------+-----------+

4 no mistakes 3 few mistakes 2 many mistakes 1 incomplete (however is
present) 0 not evident or not included

Percentages: Information Presentation Teamwork \_\_\_\_\_\_\_\_ Overall
\_\_\_\_\_\_\_\_