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explore the forest floor

Tutorial Questions are divided into three sections: Forest Floor, Humus Forms and Multiple Choice. Answering the questions in these tutorials will help you to explore the website, which in turn will be useful to completing your forest floor laboratory assignment.

  • Forest Floor
  • Humus Forms
  • Multiple Choice
  • Answer Keys

Forest Floor


1. In what types of locations will O horizons be found? Would you expect to find O horizons at UBC? Why or why not?

2. List 3 ways the forest floor influences soil properties. View the definitions page and the” In the Ecosystem” video.

3. List three properties of litter that will influence what type of decomposer communities will be present in a sample. Part 3 of the “Humus Form Orders” videos gives a good overview of this.

4. Describe the typical structure of an Fm horizon, an Fz horizon. See the Classification – Description page for explanations of how to assess structure and other properties of organic horizons.

5. What is meant by the Character of an organic horizon? What would you expect to be the character of an H horizon? Big hint around 1:54 of the “Organic Horizons” video. Keep watching to answer question 6

6. In what range does the organic matter content in an organic horizon fall? (By mass).

7. Name any flora or fauna you would expect to see in an Fm horizon, in and Fa horizon? How will this affect properties of the forest floor?

8. Where would you expect the thickest forest floors to form? The thinnest? Why is this so? See Forest Floor Definition.

9. What differentiates the forest floor from mineral soil?

10. Organic Horizons:

  1. Aide in water retention
  2. Provide Nitrogen, Phosphorus and Sulfur among other nutrients to plants and microbial communities
  3. Store carbon
  4. May indicate ecological conditions or changes
  5. All of the above
  6. a, b and c

Humus Forms


    1. Review the following incomplete Humus Form Descriptions. Determine the type of F horizon (Fm, Fz, Fa) and Humus Form Order (Mor, Moder, Mull) for each description.
      1. Humus Form Description A
      2. Humus Form Description B
      3. Humus Form Description C
    2. What are the characteristic horizons of each of the Humus Form Orders?
    3. Describe the typical F horizons (if present) of each Humus Form Order.(See the Organic Horizons Page)
    4. View the following video sections: Humus Forms Part 2 (1:21-3:00) and How to Sample (1:12-1:16). Visually compare the humus forms. The mull described in the “Humus Forms” video was sampled nearby but is somewhat dissimilar to the sample taken in “How to Sample.” In fact one of the samples may not be a mull, but a type of moder called mullmoder. Which sample is it and how is a mullmoder different from a mull?
      What are the characteristic horizons of each?
    5. Name the mineral horizon that appears on the Horizons page. Why is this horizon included?
    6. Describe the typical colour and structure of this horizon.
    7. In what range does the organic matter content of this horizons fall? (By mass).

Multiple Choice


1. The difference between O horizons and L,F, and H horizons is:
a. Organic matter content
b. Saturation
c. Colour and structure

2. Non-conforming materials include:
a. B and C horizons
b. Material that has undergone disturbance
c. Charcoal, wood and coarse mineral fragments
d. Materials with unusual texture and structure

3. The characteristic horizon of a Mull humus form is:
a. Fm
b. Fz
c. Ah
d. Hh

4. Fa horizons may be found in which humus form order?
a. Mor
b. Moder
c. Mull
d. Forest Floor

5. The F in F horizon stands for:
a. Ferrous
b. Fibric
c. Fermented
d. b and c

6. Organic Horizons:
a. Aide in water retention
b. Provide Nitrogen, Phosphorus and Sulfur among other nutrients to plants and microbial communities
c. Store carbon
d. May indicate ecological conditions or changes
e. All of the above
f. a, b and c

7. Within which humus form order does the profile in this image fall? (attach)
a. Mor
b. Moder
c. Mull
d. Folisol (What is a Folisol? Check it on Description page)

Refer to the humus form descriptions from Humus Forms question 1 to answer questions 8 and 9.

8. Which combination of soil fauna appeared the Ah horizon of Description (b)?
a. Termites, centipedes and ants
b. Nematodes, fly larvae and mites
c. Spiders, Earthworms and beetles

9. Which of the three descriptions indicates having the greatest root abundance? a, b or c?

10. In order from most to least decomposed:
a. L,F,H
b. Ah, H
c. H,F,L
d. Fm,Fz,Fa

Forest Floor