1. THE SOIL FOOD WEB
Copyright restrictions for photos in this presentation:
The text and non-photo graphics are products of the USDA Natural Resources Conservation Service (NRCS). They may be used freely. Credit the USDA Natural Resources Conservation Service.
Some photos are from the NRCS or ARS and may be used freely. Credit the USDA Natural Resources Conservation Service or USDA Agricultural Resource Service as appropriate.
Photos from non-government sources were lent to the NRCS for use in the Soil Biology Primer and this slide set. Other uses may be restricted. Contact original source for permission.
Credit (for this slide only):
Courtesy of USDA Natural Resources Conservation Service.
File names (for this slide only):
MITEgray
Handlowres
amoeba

2. Soil Biology and the Landscape
When you look across a landscape, imagine the microscale habitats and complex ecosystem under the surface.
Credits:
(drawing) S. Rose and E.T. Elliott;
(photo) Arlene J. Tugel, USDA-NRCS
File names: Rose, grass

3. The Soil Food Web
Most people are familiar with the above-ground food web: Plants are eaten by herbivores are eaten by carnivores, and so on. But most plant matter is not eaten by herbivores; it is decomposed by the underground food web. All plants depend on the soil food web for their nutrition.
File name: A-3 (145KB). (Also fw.jpg 574K, and fwb.jpg at 422K)
Image courtesy of the USDA-NRCS.

4. Components of Soil Organic Matter
Decomposing organic matter
(active
fraction)
33% - 50%
Stabilized organic
matter
(humus)
Fresh
residue
<10%
Living organisms <5%
Photo credit: Collohmannia sp. Roy A. Norton, College of Environmental Science & Forestry, State University of New York
File name: M8 Mites and Leaf

5. Rhizosphere
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

6. Microbial Biomass with Depth
File name: A KB (Also depth.jpg at 170K)
Image courtesy of USDA-NRCS

7. Seasonal Microbial Activity
File name: A-7, 250KB (also Season.jpg at 1917K)
Image credit: USDA-NRCS.

8. FOOD WEB & SOIL HEALTH
Many effects of soil organisms are a result of the interactions among organisms, rather than the actions of individual species.
This implies that managing for a healthy food web is not primarily a matter of inoculating with key species, but of creating the right environmental conditions to support a diverse community of species.
Photo: A predacious mite (Labidostomatidae) feeds on a springtail.
Photo credit: Roy A. Norton, State University of New York at Syracuse.
File names: predacious mite, M10 Mite & springtail

9. Biomass of Soil Organisms in Four Ecosystems
File name: biomassB.jpg, 237K (Also: Biomass.jpg at 299K and B-1 at 740KB)
Image credit: USDA-NRCS.

10. Typical Numbers of Soil Organisms in Healthy Ecosystems
Ag Land
Prairie
Forest
Organisms per gram (teaspoon) of soil
Bacteria
100 mil. -1 bil.
Fungi
Several yards
10s – 100’s of yds
1-40 miles
(in conifers)
Protozoa
1000’s
100,000’s
Nematodes
10-20
10’s – 100’s
100’s
Organisms per square foot
Arthropods
< 100
10,000-25,000
Earthworms
5-30
10-50
(0 in conifers)
Each type of ecosystem has a characteristic food web structure.
Credit: USDA Natural Resources Conservation Service

11. Methods for Measuring the Food Web
Counting
Direct counts of individuals
Plate counts of colonies
Activity levels
Respiration (CO2 production)
Nitrification rates
Decomposition rates
Cellular constituents
Biomass C, N, or P
Enzymes
Phospholipids
DNA and RNA

12. Bacteria with fluorescent stain for counting
Credit for both photos: Serita Frey, The Ohio State University
File names: SF4 bact.jpg, SF1 bact.jpg

13. A Complex Food Web
Image credit: USDA-NRCS. Source: Elaine Ingham and Andrew Moldenke.
File name: CompFW.jpg, 509K. (Also: CompFWa.jpg at 478K, and ComplexWeb.eps at 272K.)

14. Complexity of the Soil Food Web in Several Ecosystems
File name: Funct.jpg 382K
Image credit: USDA-NRCS

15. Learning about the relationship between soil management and the soil food web requires the observations and field trials of land managers along with formal research.
Credit: Arlene Tugel, USDA-NRCS Soil Quality Institute

16. BACTERIA
Photo credit: Michael T. Holmes, Oregon State University, Corvallis
File name: PBUT

17. Bacteria
Bacteria are the specs on the fungal hyphae. The thicker, upright objects are root hairs.
Credit: R. Campbell. In R. Campbell Plant Microbiology. Edward Arnold; London. Pp. 116 and 149.
Used with the permission of Cambridge University Press

18. Nitrogen-fixing Bacteria
Nodules formed where Rhizobium bacteria infected soybean roots.
File name: Nods on Beans.jpg 277K (Also C-2 at 580K shows whole box.)
Photo credit: Stephen Temple, New Mexico State University.

19. Actinomycetes Bacterial cells that grow like fungal hyphae
Photo credit: No. 14 from Soil Microbiology and Biochemistry Slide Set J.P. Martin, et al., eds. SSSA, Madison, WI
File name: SSSA14
Bacterial cells that grow like fungal hyphae

20. Bacteria vs. fungi
In many systems, including grasslands and agricultural fields, the biomass of bacteria dominates the biomass of all other soil organisms. Fungi dominate the soil biomass of forest systems.

21. FUNGI
Credit: Serita Frey, The Ohio State University
File name: SF6

22. Fungi and Soil Quality Decompose carbon compounds
Improve OM accumulation
Retain nutrients in the soil
Bind soil particles
Food for the rest of the food web
Mycorrhizal fungi
Compete with plant pathogens
Photo credit: No. 48 from Soil Microbiology and Biochemistry Slide Set J.P. Martin, et al., eds. SSSA, Madison WI.
File name: SSSA48

23. Mycorrhizal structure
Mycorrhizae
Tree root
Photo credit: Randy Molina, Oregon State University, Corvallis.
File name: M4 Fungi LR.jpg, 328K
Fungal hyphae
Mycorrhizal structure

24. Ectomycorrhizae
Photo Credit: USDA, Forest Service, PNW Research Station, Corvallis, Oregon.
File name: Ectomy~1

25. Arbuscular Mycorrhizae (AM)
File name: VAM LR.jpg 205K
Photo Credit: Elaine R. Ingham, Oregon State University, Corvallis.

26. File name: JER LR.jpg, 290K
Photo Credit: Jerry Barrow, USDA-ARS Jornada Experimental Range, Las Cruces, NM.

27. Mushrooms: The fruiting body of some fungi
File name: tettleshroom LR.jpg, 234K
Photo courtesy of USDA-Natural Resources Conservation Service.

28. Mycorrhizal Fungi
Endophytes (similar to mycorrhizae) and polysaccharides secreted by the plant and fungi bind sand to the root.
Photo Credits: Jerry Barrow, USDA-ARS Jornada Experimental Range, Las Cruces, NM.
File names: BWSHEATH
COL-SH~1

29. PROTOZOA Ciliates Amoebae Flagellates Largest of the three types
Move by means of hair-like cilia
Eat the other protozoa and bacteria
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 three
Move by means of a few whip-like flagella.

30. PROTOZOA File name: Testate amoeba LR.jpg, 179K
Credit: Elaine R. Ingham, Oregon State University, Corvallis

31. Flagellate File name: vorticella prot LR.jpg, 278K
Credit: Elaine R. Ingham, Oregon State University, Corvallis.

32. Ciliate File name: ciliate2 LR.jpg 294K
Credit: Elaine R. Ingham, Oregon State University, Corvallis

33. Amoebae Photo credits:
(brown photo) No. 35 from Soil Microbiology and Biochemistry Slide Set J.P. Martin, et al., eds. SSSA, Madison, WI
(blue photo) Michael T. Holmes, Oregon State University, Corvallis. (Not used in the Primer.)
File names:
(blue photo) AMOE
(brown photo) SSSA35

34. Mineralization and Immobilization
Organisms consume other organisms and excrete inorganic wastes.
Organic nutrients are stored in soil organisms and organic matter.
Inorganic nutrients are usable by plants, and are mobile in soil.
File name: MinImmB.jpg, 51K. (Also: MinImmA.jpg at 100K, and E-2 at 375KB)
Image courtesy of USDA-Natural Resources Conservation Service
Organisms take up and retain nutrients as they grow.

35. 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.)

36. NEMATODES File name: large todes LR.jpg, 262K
Credit: Elaine R. Ingham, Oregon State University, Corvallis.

37. NEMATODES 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

38. Predatory Nematode File name: predatory tode LR.jpg 254K
Credit: Kathy Merrifield, Oregon State University, Corvallis.

39. Root-feeding nematodes
Upper left (blue) is the lesion nematode, Pratylenchus.
Lower right is the root-feeding nematode, Trichodorus.
File names:
Upper Left (blue): rootfeedingtode prat LR.jpg, 233K
Lower right: rootfeedingtode trich LR.jpg, 184K
Credits:
Upper Left, blue: Kathy Merrifield, Oregon State University, Corvallis.
Lower right, green: Elaine R. Ingham, Oregon State University, Corvallis.

40. ARTHROPODS Collohmannia sp.
Photo credit: Roy A. Norton, State University of New York at Syracuse.
File name: M12

41. Mites and Biodiversity
Credit: Valerie Behan-Pelletier, Agriculture and Agri-Food Canada.
File name: VBPmites LR.jpg 287K

42. Types of Arthropods
Shredders
Predators
Herbivores
Fungal-feeders

43. Shredders: millipedes
The millipede on the light background is Orthoporus ornatus.
Photo Credits:
(beetle) A. Beaumont, Lowestoft
(millipede, brown background) No. 41 from Soil Microbiology and Biochemistry Slide Set J.P. Martin, et al., eds. SSSA, Madison, WI
(millipede, light background) David B. Richman, New Mexico State University.
File names:
(beetle) INSECT~3
(millipede) SSSA41
(millipede, light background) Orthopor 472K

44. Predators (1)
(group of ants) Rugose harvester ants. Pogonomyrmex rugosus
Photo credits:
(Ant) David Houghton (not used in the Primer)
(Group of ants) David B. Richman, New Mexico State University, Las Cruces.
File names:
DH ant

45. Predators (2): Pseudoscorpions
With green background is a Homosphyronid.
Credits:
(green) David B. Richman, New Mexico State University, Las Cruces.
File names:
(green) Pseudo4 (461K)
(yellow body) Pseudoscorpion.jpg

46. Predators (4): Centipedes
Photo credits:
(brown) No. 40 from Soil Microbiology and Biochemistry Slide Set J.P. Martin, et al., eds. SSSA, Madison, WI
(gray) David Houghton
File names:
(brown) SSSA40
(gray) DH centipede

47. Predators (5) Wolf spider
Photo Credit: Trygve Steen, Portland State University, Portland, Oregon.
File name: M6B

48. Herbivores Photo credits:
(symphylan) Ken Gray Collection, Department of Entomology, Oregon State University, Corvallis.
File names:
(symphylan) M11 Symphylan

49. Springtails (fungal feeders)
Abundant in many soils.
Feed on some disease-causing fungi.
Jump by slamming their tail down.
Photo credits:
(light microscope) Andrew R. Moldenke, Oregon State University, Corvallis.
File names:
(light microscope) M7B

50. What is in Your Soil? Pitfall trap Berlese funnel
Burlese funnel – Heat from a light bulb dries soil and drives small arthropods into the cup below. Pitfall trap – Large arthropods fall into a cup buried with the rim even with the soil surface.
(Click on “Reset Picture” to restore white background behind the drawings.)
File names: berlese.jpg 139K, pitfall.jpg 92K
Images courtesy of the USDA-Natural Resources Conservation Service
Berlese funnel

51. EARTHWORMS
Photo credit: Clive A. Edwards, The Ohio State University, Columbus.
File name: CD1 ew bunch

52. Earthworms bury litter
Photo credit: Soil and Water Management Research Unit, USDA-Agricultural Research Service, St. Paul, Minnesota.
File name: LW leaf in burrow

53. Earthworm burrow
Photo credit: Clive A. Edwards, The Ohio State University, Columbus.
File name: CE3 burrow

54. Vertical burrows
Photo and image credit: North Appalachian Experimental Watershed, USDA-Agricultural Research Service, Coshocton, Ohio

55. Earthworm casts
Photo credit: Soil and Water Management Research Unit, USDA-Agricultural Research Service, St. Paul, Minnesota
File name: LW6a casts

56. Earthworm burrow opening
Photo credit: Clive A. Edwards, The Ohio State University, Columbus
File name: CE7a2, 303K

57. Earthworm burrow opening
Midden pile
Photo credit: North Appalachian Experimental Watershed, USDA-Agricultural Research Service, Coshocton, Ohio
File name: MS7b
Burrow opening

58. Reproduction
Credit for both photos: Clive A. Edwards, The Ohio State University, Columbus
File names:
CE8a-cocoon
CE8c mating