Pink fireweed flowers blooming in front of the black trunks of a burned forest

ENVIRONMENTAL SCIENCE · CHAPTER 5

Ecological Succession Lab

Follow along with your worksheet, one question at a time.

mrsajdak.com/succession

Photo: U.S. Fish and Wildlife Service

BEFORE YOU START

Two ways to start over

A large grey boulder covered in pale patches of lichen

Bare rock

No soil. No seeds. No roots. Life starts from nothing. This is primary succession.

An empty street corner where houses once stood, now grown over with grass and young trees

Empty city lot

The house is gone. The soil stays, full of seeds and roots. This is secondary succession.

The five stages

1. Pioneers

2. Grasses and wildflowers

3. Shrubs

4. Sun-loving trees

5. Mature forest

Each stage changes the place for the next one.

Both can end as a forest. Which gets there first, and by how much?

Photos: Gary Houston, CC0 · Nyttend, public domain

BEFORE YOU START

Get set up

Open mrsajdak.com/succession on your device.

Write your name, the date and your period on the worksheet.

Find the three tabs at the top of the lab. Each tab goes with one part of the worksheet.

Start on Tab 1. Do not skip ahead.

The top of the lab page, showing the title and three tabs: Fast-forward a place, Disturb it, Mount St. Helens

Tab in the lab	Worksheet	Questions
1. Fast-forward a place	Part 1	1 to 5
2. Disturb it	Part 2	6 to 11
3. Mount St. Helens	Part 3 and Wrap it up	12 to 16

Screenshot: mrsajdak.com/succession

Bare layered rock with bright orange lichen growing across it

TAB 1 · QUESTIONS 1 TO 5

Part 1. Fast-forward a place

Succession is the slow change in what lives in a place.

You will run two places through hundreds of years. Watch what shows up first.

Photo: gailhampshire, CC BY 2.0

PART 1 · TAB 1

Run a place through time

Pick Bare rock.

Press Play. Or drag the year slider.

Watch the box in the corner of the picture. It shows the year, the stage and the numbers.

Go all the way to the end. The rock ends at year 600.

Then pick Empty city lot. Run it to the end too. The lot ends at year 150.

The Pick a place box in the lab: buttons for Bare rock and Empty city lot, a year slider, Play, step buttons, Skip to the end and Measure this year

The empty city lot at year 12: shrubs growing on dark soil between two houses

The −1, +1, −10 and +10 buttons move a few years at a time.

Skip to the end jumps to the last year.

Screenshots: mrsajdak.com/succession, Tab 1

PART 1 · QUESTION 1

When does each stage begin?

Find the Stages reached box in the lab.

Copy the year each stage begins. Do the rock column and the lot column.

For each stage, divide the rock year by the lot year.

Write how many times as long the rock takes.

The Stages reached box in the lab: a table of the five stages with a column for Bare rock and a column for City lot

Example

A stage begins in year 80 on the rock.

It begins in year 4 in the lot.

80 ÷ 4 = 20

The rock takes 20 times as long.

These are not your numbers. Use your own.

Screenshot: mrsajdak.com/succession, Tab 1

PART 1 · QUESTION 2

Measure year 20 and year 100

Pick Bare rock. Set the year to 20. Use the slider, then the +1 and −1 buttons.

Press Measure this year.

Set the year to 100. Measure again.

Do the same two years for the city lot.

Copy the four rows from Your measurements.

The Your measurements box in the lab, with one row showing place, year, soil, species, tallest plant and cover

Soil depth	How deep the soil is, in cm.
Plant species	How many kinds of plants live there.
Tallest plant	Check the unit. It may be cm or m.
Plant cover	How much of the ground has plants on it.

Screenshot: mrsajdak.com/succession, Tab 1

PART 1 · QUESTIONS 3 TO 5

Explain what you saw

QUESTION 3

First

Pioneer species

Go back to bare rock. Look at the first 50 years.

What living things show up first? How do they start to make soil?

QUESTION 4

5 ×

Why is the lot faster?

The lot gets to a mature forest about 5 times faster.

Compare the soil at year 20 in your Question 2 table. Use a number.

QUESTION 5

Peak

Up, then down

On the graph, press Plant species. Read the top of the lot’s line. Then read the end.

Think about what tall trees do to the ground under them.

A firefighter standing in tall dry grass in front of a wall of flames during a planned prairie burn

TAB 2 · QUESTIONS 6 TO 11

Part 2. Disturb it

A disturbance is something that damages a community. A fire, a flood, a windstorm, a bulldozer.

You will hit three communities. Then you will time how fast each one comes back.

Photo: U.S. Fish and Wildlife Service

PART 2 · TAB 2

Three communities

A wide flat prairie of green grass and purple wildflowers

Grassland

Grasses and wildflowers. Few trees.

A green forest of tall leafy trees with ferns and small plants on the ground

Temperate forest

Trees that drop their leaves in fall. Like the woods near Buffalo.

Rain forest

Warm and wet all year. Very tall trees.

Which is hardest to damage? Which comes back fastest? Is it the same one?

Photos: Jasper Shide, CC0 · Great Smoky Mountains National Park · Vyacheslav Argenberg, CC BY 4.0

PART 2 · TAB 2

Predict, then run

In Set it up, pick the community and the disturbance. Pick Large (all).

In Predict first, pick how much it will change. Pick how fast it will come back.

Press Run. Or press Skip to the end.

Find Your runs. Copy Change and Back to 90%.

The Set it up and Predict first boxes in the lab: buttons for the community, the disturbance, how much of the plot it hits, and two predictions

A temperate forest in the lab during a flood, with water covering the ground under the trees

The disturbance hits in year 5. The run ends at year 80.

A wrong prediction is fine. Make it before you run.

Screenshots: mrsajdak.com/succession, Tab 2

PART 2 · QUESTION 6

Your six runs

Run	Community	Disturbance
1	Grassland	Fire
2	Grassland	Cleared
3	Temperate forest	Fire
4	Temperate forest	Cleared
5	Rain forest	Fire
6	Rain forest	Cleared

The Your runs box in the lab: one row showing the run, its change, its years back to 90 percent and the percent at year 80

Change is how much the community dropped.

Back to 90% is how many years it took to recover. If the lab says not in 80 yr, write that.

Screenshot: mrsajdak.com/succession, Tab 2

PART 2 · QUESTIONS 7 TO 9

Two different strengths

QUESTION 7

Inertia

Hard to damage

Surviving a disturbance without changing much.

Look at your fire columns. Which community changed the least? Give its number.

QUESTION 8

Resilience

Quick to come back

Being restored after a severe disturbance.

Look at your cleared columns. Which came back fastest? Which was slowest? Give numbers.

QUESTION 9

Agree?

“Hard to damage means fast to bounce back.”

Find the rain forest’s two numbers: its change in a fire, and its years back after clearing.

Argue for or against.

PART 2 · QUESTIONS 10 AND 11

Size, and a different kind of trouble

QUESTION 10

Does size matter?

Run Temperate forest, Windstorm, Small (25%). Write the change.

Run it again at Large (all). Write the change.

How does a bigger disturbance change the effect?

QUESTION 11

An invader moves in

Run Temperate forest, Invasive plant, Large.

Write the native plants at year 80. It is the last column in Your runs.

A fire ends. What about an invader?

The lab graph of native plants as a percent of before: the line drops at the disturbance in year 5 and climbs back over the dotted 90 percent line

The graph shows native plants as a percent of before.

The dotted line is 90%. Back over the line means recovered.

Screenshot: mrsajdak.com/succession, Tab 2

A grey hillside covered with thousands of trees knocked flat by the 1980 blast, with two scientists standing among them

TAB 3 · QUESTIONS 12 TO 15

Part 3. Mount St. Helens

On May 18, 1980, this volcano in Washington State erupted. The blast knocked whole forests flat.

Ecologist Roger del Moral went back almost every summer to measure the plants. These are his real numbers.

Photo: Lyn Topinka, U.S. Geological Survey

PART 3 · QUESTION 12

Read the real data

Pick a site. Start with Studebaker Ridge.

Slide to the first year the site was measured. The note under the site names tells you when the plots were set up.

Press Record this year. Copy the plant cover.

Do the same for 1990. Then for the last year measured.

Repeat for Pine Creek and Butte Camp.

The Pick a study site box in the lab: buttons for Studebaker Ridge, Pine Creek and Butte Camp, a note about the site, a year slider and a Record this year button

A map of Mount St. Helens with the three study sites marked, beside a grid of 100 squares where the green squares show plant cover

Each square is 1% of the ground. Green squares have plants.

No survey that year? The lab shows the last one and tells you.

Screenshots: mrsajdak.com/succession, Tab 3

PART 3 · QUESTION 12

The first year at 10%

Look at the graph. Find the dotted line at 10% cover.

Follow one site’s line. Find the first dot on or above the dotted line.

Move the slider to that year. Check the number.

Subtract 1980. That is the years after the eruption.

The lab graph of plant cover after the eruption from 1980 to 2010, with one line for each site and a dotted line at 10 percent cover

Example

1987 − 1980 = 7

A site that first reaches 10% in 1987 took 7 years. Not your numbers.

Screenshot: mrsajdak.com/succession, Tab 3

PART 3 · QUESTION 13

What did 1980 leave behind?

Primary succession

Nothing was left. No soil, no roots, no seeds.

Secondary succession

The plants were gone. Soil, roots or seeds were still there.

Plants mostly survived

Most plants were hurt, not killed.

Read the note under the site names for each site. Tick one box in each row. Then give evidence for one row. Say what was left, or use a number from Question 12.

The Pick a study site box in the lab, with the note that describes what the eruption did to the site

The note changes when you pick a different site.

Screenshot: mrsajdak.com/succession, Tab 3

PART 3 · QUESTIONS 14 AND 15

A pioneer, and a prediction

A low plant with silvery leaves and purple flowers growing on bare grey volcanic gravel

QUESTION 14

Name the pioneer

Pick Studebaker Ridge. Look at Most common plants in the plots from 1984 to 1994. Write the plant at the top.

Bacteria in its roots add nitrogen to the ground. How does that help the plants that come later?

QUESTION 15

Predict 2040

Use Predict 2040 in the lab. Will cover be higher, lower or about the same as in 2009? What moves in next?

Use the pattern in the graph as your reason.

Photo: brewbooks, CC BY-SA 2.0

WRAP IT UP · QUESTION 16

Does a forest always grow back the same way?

The claim

“When a forest is destroyed, it always grows back the same way, at the same speed.”

From Part 2

Pick a number from your Question 6 table. Two communities with the same disturbance work well.

From Part 3

Pick a number from your Question 12 table. Two sites on the same volcano work well.

Reasoning

Say what was different about the places. Think about what was left behind.

Red and purple wildflowers growing among grey rocks, with Mount St. Helens in the distance

Wildflowers below Mount St. Helens in 2004, 24 years after the eruption.

Photo: P. Frenzen, U.S. Forest Service

Tall dead tree trunks left from 1980 standing over young green forest, with Mount St. Helens behind

LAST CHECK

Before you hand it in

Name, date and period are on top.

All four tables are full.

Question 13 has one tick in each row.

Every claim uses numbers from your own tables.

Photo: USDA Forest Service, Pacific Northwest Research Station