Biology

1. BIOL 403: SOIL ECOLOGY
 Soil is the topmost portion of the earth that comprises both
biotic and abiotic components.
 Soil Ecology is the study of interaction between biotic and
abiotic components of the soil environment.

2. What is soil biology?
What role does it play in soil
quality?

3. Soil organisms are involved in nearly
every aspect of soil quality
Organic
matter
Nitrate
Leaching
Soil
Community
Nutrient cycling
Structure/Aggregation
Humification
Decomposition

4. In order to understand how biology
affects our soils - we need to
understand a little about the
organisms who live there
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.

5. Water
Soil particles Plant roots
Soil is a habitat

6. Soil is alive…
For example, in 1g of soil:
>100,000,000 bacterial cells
>11,000 species of bacteria
Also fungi and larger animals

7. Who’s there?
Macrofauna:
Soil ‘Engineers’

8. Termite
Snail
Earthworm
Vole
Soil Animals
Centipede
Pseudoscorpion

9. 1. Decomposition
(shredding residues)
2. Mixing soil (aeration)
Decomposition rate of blue grama (Bouteloua gracilis)
Soil animals are important for

10. Who’s there?
Mesofauna:
Soil predators,
pathogens,
herbivores

11. Soil mesofauna
Nematodes
Mites
Protozoa
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.

12. Soil mesofauna
Nematodes
Mites
Protozoa
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Soil mesofauna are important for
1. Residue decomposition
1. Predation
1. Pathogenesis

13. Microorganisms:
Soil process
controllers

14. Soil microorganisms
Fungi
Bacteria
Fungi

15. QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Fungi
• Filamentous growth
What are the advantages of
filamentous habit?

16. Fungi
• Filamentous growth
• Functionally critical!
-Wood degrading
-Mycorrhizal association
•myco (fungus) +
rhiza (root)
(Symbiotic structure
formed by a fungus
plus a plant)

17. Source: Harrison et al 1999
Roots without mycorrhizae

18. Source: Harrison et al 1999
Roots with mycorrhizae

19. Bacteria
• Small, single celled
~2µm
What is the importance of small size?

20. Bacteria
• Small, single celled
• Abundant
Bacteria
Fungi
Conventional
tillage
No-till
Prairie
Forest

21. Diversity in soil is important for
nitrogen cycling.

22. Relationship to soil quality?

23. Diversity may be important in response to management