1. Who lives in the soil ??
The Furrow

2. Soil is an archive of life on earth!

3. Quantifying Biodiversity
Group
Known Species
Estimated Total Species
Percentage Known
Vascular plants
220,000
270,000
81%
Algae
40,000
60,000
67%
Fungi
69,000
1,500,000 5%
Bacteria
3,000
30,000
10%
Most occur in soil
(Hawksworth, 1991)

4. Soil organisms vary widely in size
Most are tiny !!!
Soil organisms vary widely in size
Viruses
Bacteria
Fungi
Algae
Protozoa
Nematodes
Microarthropods
Enchytraeids
Earthworms
Ants, termites, spiders
Mollusks
Others: rodents, snakes,
voles, amphibians, etc.
Body size increasing
Microflora
Microfauna
Mesofauna
Macrofauna
Megafauna
Abundance

5. Body sizes and shapes are adaptations to the many different spatial niches in soil
                               
                               
                

6. BACTERIA have many different shapes cocci bacillus filamentous
SSSA
filamentous
spirilla

7. Typically > 10 billion bacteria per gram of soil

8. What do bacteria do in soil ?
Colonize aerobic and anaerobic
environments
Decompose labile substrates
Mediate redox transformations
Nourish bacterivores
Fix N

9. N-fixing nodules on a cowpea plant

10. Legume love affair
Sarrantonio

11. FUNGI have many different life forms
Yeasts
Mycelia
Fruiting bodies
Spores

12. What do fungi do in soil ? Decompose recalcitrant organic compounds
Penetrate residues
Stabilize soil structure
Nourish fungivores
Form symbioses with plant roots and soil fauna
Compete with plant pathogens
Parasitize plants and soil animals
Produce toxins e.g. aflatoxin produced by Aspergillus flavus on peanut
Photo credit: No. 48 from Soil Microbiology and Biochemistry Slide Set J.P. Martin, et al., eds. SSSA, Madison WI.
File name: SSSA48

13. Mycorrhizal diversity
Ectomycorrhizae
AM endomycorrhizae
Arbutoid mycorrhizae
Ericoid endomycorrhizae
Orchid endomycorrhizae
Lavelle and Spain (2001)

14. Mycorrhizal Networks: Connecting plants intra- and interspecifically
Many plants are connected underground by mycorrhizal hyphal interconnections.
Mycorrhizal (AM) fungi are not host specific.
Illustration by Mark Brundrett

15. Increase nutrient (P) uptake suppress pathogens
Mediate plant competition
Improve soil structure
Increase nutrient uptake
N, K, Cu, Zn, and esp. P
Enhance water
acquisition
Increase resistance to pathogens
Mediate plant competition
Improve soil structure through glomalin
All of these benefits are situation dependent
Glomalin
Superglue
of the soil ??

16. PROTOZOA Important bacterivores Ciliates Amoebae Flagellates
Largest of the protozoa
Move by means of hair-like cilia
Amoebae
Also large
Move by means of a temporary foot (pseudopod)
Include testate amoebae (with shell-like covering), and naked amoebae
Flagellates
Smallest of the protozoa
Move by means of flagella (1-2)
Important bacterivores

17. Soil-Dwelling “Vampires”
Vampyrellids are a group of amoebe that eat fungi by drilling round holes through the fungal cell wall and consumes the fluid inside.
In this picture, they attack Gaeumannomyces graminis, the fungus that causes “take-all disease” in wheat.
File name: vampraid.jpg, 451K (Also: E-4 at 1500KB, shows whole Bug Biography.)
Photo credit: Homma, Y. et al Phytopathology 69:
(Photo is in the public domain.)
Vampyrellid amoebae attacking Gaeumannomyces graminis, the fungus that causes “take-all disease” in wheat.

18. NEMATODES Most abundant of the soil fauna Functionally diverse
Bacterivores
Fungivores
Herbivores
Predators
Omnivores
File name: large todes LR.jpg, 262K
Credit: Elaine R. Ingham, Oregon State University, Corvallis.
Most are beneficial -
promoting
decomposition
and nutrient recycling

19. Nematode diversity Bacterivore Fungivore Predatory Plant parasitic
Top left is the bacterial-feeding nematode, Elaphonema.
Bottom right is a fungal-feeding nematode.
Photo credits: (for both) Elaine R. Ingham, Oregon State University, Corvallis
File names:
BFTODE
FFTODE
Predatory
Plant parasitic

20. Galled root system of tomato infected with root-knot nematode, Meloidogyne sp., compared with non-infected root system
Root knot juvenile penetrating a tomato root

21. Arthropods
exoskeleton
segmented body
jointed legs

22. Arthropod diversity Litter Shredders Fungivores Predators Herbivores
Collohmannia sp.
Photo credit: Roy A. Norton, State University of New York at Syracuse.
File name: M12
Predators
Herbivores

23. Microarthropods

24. EARTHWORMS
Members of phylum Annelida, earthworms and annelids best known soil inhabitants. More advanced than nematodes because they have a circulatory system- 3-4? hearts
Earthworm mass- Photo credit: Clive A. Edwards, The Ohio State University, Columbus.
File name: CD1 ew bunch
Giant earthworm from Australia; can get up to 11 feet. Also very endangered/rare

25. ~ 35 species of earthworms have been found in Illinois soils
anecic
~ 35 species of earthworms have been found in Illinois soils
~ half are exotic species from Europe and Asia
endogeic
epigeic

26. Contact Ed Zaborski at (217) 265-0330, or zaborski@uiuc.edu by e-mail
A new earthworm parasite has arrived in IL
Before earthworms invaded
After earthworms invaded
A new earthworm predator has arrived in IL
The geographic distribution of Bipalium adventitium in Illinois is unknown. Home gardeners and nursery workers may see these exotic land planarians under boards and stones or crawling on the soil surface after rains. They are up to 2.5 inches long and 1/8 of an inch wide when crawling. They are pale brown or tan with a thin dark brown line running down their back. Scientists would appreciate receiving reports of any observations of these creatures.
Contact Ed Zaborski at (217) , or by

27. Epigeic species can be used for vermicomposting

28. Earthworm cocoons

29. How do earthworms move through soil ?
Loose soil
They insert their anterior tip into a pore, extend their setae to anchor most of their body and then exert radial and longitudinal pressure. A cycle of alternating contractions and relaxations thrusts their body forward.
Dense soil
They invert their pharynx, exude lubricating mucus and suck obstructive soil into their body.

30. How do earthworms eat ?
Earthworms eat by pulling food into their mouth with their prostomium (mouth) and pharynx which creates a very strong suction.
The food is stored in the crop and then ground up into small digestible pieces in the gizzard.
Earthworms need a gizzard because they do not have any teeth. Nutrients are absorbed in the small intestine.

31. Where are the soil organisms ??

32. Soil organisms are concentratedin
HOT
SPOTS !
drilosphere
porosphere
The rhizosphere is the narrow region where roots and soil meet. Soil biological activity is concentrated here. This photo shows cells, proteins, and sugars being released by the young root tip.
Credit: No. 53 from Soil Microbiology and Biochemistry Slide Set.1976 J.P. Martin, et al., eds. SSSA, Madison, WI.
File name: SST
detritusphere
aggregatusphere
rhizosphere
Adapted from Coleman et al. (19??)

33. casts
middens
Drilosphere
Zone of
earthworm
influence

34. Which burrows were made by an endogeic ?
Capowiez et al. 2003)

35. In 1881, Darwin reported that healthy earthworms sometimes leave their burrows at night and embark on a “voyage of discovery”
Surface migration is a routine activity aimed at dispersal and finding a mate. Surface migration usually occurs during cloudy moist conditions. Both anecic and endogeic earthworms are active surface migrants.

36. Rhizosphere
< 10 % of soil volume
Zone of root influence

37. Navigating the rhizosphere
Rhizoplane
End of the rhizosphere
Endo-Rhizosphere
Root free soil
Ecto-Rhizosphere
> 90% of soil volume
< 10% of soil volume
(Lavelle and Spain, 2001)

38. Detritusphere
surface residue
zone

39. The soil matrix presents its inhabitants with many challenges
Tortuous, loosely connected and highly constricted porosity
Structural
rigidity
The soil matrix presents its inhabitants with many challenges
Low quality
nutritional
resources
Moisture fluctuations

40. Microorganisms have very limited ability to move within the soil matrix.

41. For their prince charmings to arrive !
As a result,
most soil microorganisms are in a dormant state
For their prince charmings
to arrive !
waiting…

42. There are many types of prince charmings
Rain
Roots
There are many types of prince charmings
Organic
amendments
Tillage

43. Soil fauna have a disproportionate impact on nutrient cycling, energy fluxes and plant growth
>90%
metabolic
activity

44. Soil fauna are relatively mobile but have limited digestive ability
3 main types of digestive interactions
occur between soil fauna and microflora
Soil microflora are relatively immobile but have almost unlimited digestive ability

45. I want some bacteria for lunch !
Microbivory
NH4+
NH4+
NH4+
NH4+
NH4+
NH4+
I want some bacteria for lunch !
Microfauna (e.g. protozoa and nematodes) harness the microflora’s digestive abilities by grazing on them

46. External rumen digestion
The fecal pellets of many mesofauna contain shredded, moistened and mixed but largely undigested residues
Reingestion of fecal pellets after a few days of microbial activity greatly increases assimilation

47. Soil macrofauna are ecosystem engineers
Rumen digestion greatly enhances utilization of complex substrates by soil macrofauna
Soil macrofauna are ecosystem engineers

48. Impact of tillage on the soil food web
Adapted from Hunt et al. (1986)

49. Soil organic matter fuels the soil food web

50. Active OM energizes biologically mediated processes

51. Biologically active SOM
SOM is a complex mixture
Living organisms
Biologically active SOM
Recent residues
Recalcitrant
SOM
HUMUS
Adapted from Magdoff and Weil (2003)