Who lives in the soil ??

1. Who lives in the soil ?? The Furrow

2. Soil is an archive of life on earth!

3. Quantifying Biodiversity Most occur in soil (Hawksworth, 1991)

4. 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. SSSA BACTERIA cocci have many different shapes bacillus 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. FUNGIhave 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

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 Glomalin Superglue of the soil ??

16. PROTOZOA Important bacterivores

17. Soil-Dwelling “Vampires” Vampyrellid amoebae attacking Gaeumannomycesgraminis, the fungus that causes “take-all disease” in wheat.

18. NEMATODES • Most abundant of the soil fauna • Functionally diverse Bacterivores Fungivores Herbivores Predators Omnivores • Most are beneficial - promoting decomposition and nutrient recycling http://nematode.unl.edu/hdigonic.htm

19. Nematode diversity Bacterivore Fungivore 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 http://www.agnr.umd.edu/users/nrsl/entm/nematology/images/eis143.jpg

21. Arthropods exoskeleton segmented body jointed legs

22. Arthropod diversity Litter Shredders Fungivores Predators Herbivores

23. Microarthropods

24. EARTHWORMS

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

26. A new earthworm parasite has arrived in IL After earthworms invaded Before earthworms invaded A new earthworm predator has arrived in IL The geographic distribution of Bipalium adventitiumin Illinois is unknown. Home gardeners and nursery workers may see these exoticland 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) 265-0330, or zaborski@uiuc.edu by e-mail

27. Epigeic species can be used for vermicomposting

28. Earthworm cocoons http://soils.usda.gov/sqi/soil_quality/soil_biology/images/CE8a-cocoon_LR_small.jpg

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 concentrated in HOT SPOTS ! porosphere drilosphere detritusphere aggregatusphere rhizosphere Adapted from Coleman et al. (19??)

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

42. 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. Microbivory NH4+ NH4+ NH4+ NH4+ NH4+ I want some bacteria for lunch ! NH4+ 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. 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