1. Importance of Soil Arthropods
Dr. Andrew Moldenke
Dept. of Botany
Oregon State University
Importance of Soil Arthropods
Special thanks to Dr. Moldenke for presentation notes provided during the 2009 HJ Andrews LTER summer workshop.

2. Three thin-sectioned soils
Note: 70-80% of all arthropod species in the world live in the soil (terrestrial ecosystems)
Note: Small white areas are micropores for storing water; large white areas are macropores for storing Oxygen and air
Note: Between the top and bottom layers of leaves have been eaten by turtle mites
Note: Really large dark blobs are earthworm poop

3. Thin-section clear cut soil
Note: Clear cut soil will have little water holding capacity; not only are you changing the vegetation but how the ecosystem functions

4. Thin section mature forest soil
Note: Forest (old growth) soil poop will have a surface area is infinitely greater
Question: Why is the size and density of bug poop important?
Answer : Bacteria and fungi will feed on the surface of the arthropod poop and release nutrients. The more poop, the more surface area of the poop, the more bacteria will feed on the poop and release more nutrients.

5. I have shown that species richness of soil arthropods is SOOO large that anyone can take a sample of forest litter (dead leaves) and soil from anywhere in the approximately 3,000 hectare Andrews Forest LTER---
and then, after identifying the arthropods, I can tell you…

6. what month of the year it was
altitude
soil moisture
plant community
slope face
under which species of tree
how old the forest trees are
how long since the last fire
how far from the nearest trunk

7. All that information (and more
All that information (and more!) simply in a list of the relative abundance of the species

8. Creatures that live in the soil are very sensitive to abiotic and biotic factors
therefore excellent for use as biological indicators.
They have fantastic potential as indicators for determining human impacts on soil ecosystem function and for soil health.

9. species/m2 individuals/m2 forest 250 350,000 pasture 30-60 100,000
row agriculture
5-10
2 - 20,000
Note: Each and every shovelful of forest dirt has 250 species per square meter or 350K individuals. As soil is impacted more (pasture, agriculture…) the number of species decline.

10. Indicators of change in the productive potential of soil is great but I want to talk about 2 other things today.
Biodiversity for its own sake. We never bother to take the time to look at these organisms, but they are some of the most fascinating animals around! WOW! FANTASTIC!
2. They don’t just passively indicate “soil health” they are key players in the cycle of plant growth and soil nutrients themselves.
B.P.G.T.

11. Many mites

12. EACH and EVERY SHOVEL of forest dirt = all pictures that follow
250 spp/m ,000 indivs/m % of all arthropods in
most terrestrial ecosystems
120,000 little legs (Andy’s foot)
15,000 species in Oregon

13. Question: Which bugs are discussed here?
So, who cares?
Why study bugs in soil?
What do they do?
they eat and they poop
Question: Which bugs are discussed here?
Answer: Mites, springtails, and other arthropods

14. Odontodamaeus
Mites….

15. Oppiella
Mites….

16. Mites….
Epidamaeus

17. Long-legged near Damaeus
Mites….

18. Galumna open
Mites….

19. Galumna closed Mites…. Note: Defense mechanisms
Hands and legs fold in and doors close in

20. Pterochthonius
Mites….

21. Hermanniella
Mites….

22. Rearing mites

23. Small/large turtle mites
Note: Turtle mites are smaller than an eyelash

24. Oribatid chelicerae
Mites….

25. Mycorrhizae
Note: In this example, the tree feeds the fungi sugar (Carbon) and the fungi feeds the tree N, P…. the root underneath carries water, nothing gets in unless regulated by fungi

26. Mycorrhiza under the Electron Microscope

27. Isotoma
Springtails…
Notes: If attacked, the tail drops and launches the bug easily a meter.
Springtails deep in the soil are blind.

28. Diagrammatic springtail (Collembola)

29. Springtails…
Onychiurus

30. Onychiurus

31. Onychiurus, high magnification

32. Other arthropods…
Ptiliid beetle
Note: Flight apparatus is like a bird feather. ( A little rod with hairs).
forewing

33. Protura Other arthropods… Notes: 1) In all soils
Notes:
1) In all soils
2) Important in nutrient cycling
3) No common names for them
4) Evolutionally they lost their antenna, false antenna as first set of legs
Summary: When putting together foodwebs, all these bugs so far have been fungivores

34. Enchytraeid
Other arthropods…

35. Suctobelbella – bacterial-feeder
Other arthropods…
Suctobelbella – bacterial-feeder

36. Cydnidae – Burrowing bug
Other arthropods…

37. Symphyla
Other arthropods…

39. Cicindelid immature
Other arthropods…

40. Gamasid
Other arthropods…

41. Uropodid
Other arthropods…

42. Uropodid - facial view

43. Polyaspidid Other arthropods…
Note: Strings of wax secreted from the analogous of sweat glands

44. Cyta Mites… Notes: 1)Predacious mite
2) Dumped out of helicopters on caterpillars (bio- control)

45. Onychiurus being eaten by Labidostoma

46. Symphylan being eaten by Pergamasus
Note: Worst vegetative pest in the Williamette Valley

47. Pergamasus feeding (high magnification)
Notes:
1) There is a mite hitching a ride on the Pergamasus (feeding)…
2) Bacterial and fungal spores also catching rides if we looked closer, so they make the environment homogenous…
(always moving everyone in the environment around)

48. Pseudoscorpion
Note: Poison gland in tip of claw released on prey

49. Chthoniid pseudoscorpion

50. Pseudoscorpion, facial view

51. Taracus – Skunk-spider (Opilionida)
Notes:
1) Probably 400 species of spiders in OR soil
2) The largest the same size of a period on the printed page

52. Sclerobunus – skunk-spider

53. Native scorpion with young

54. Spider webs

55. Spider fangs

56. Callobius

57. Pardosa

58. Micro-spider, male

59. Antrodiaetus

60. Cicindela
Omus

61. Staphylinidae

62. Lithobiidae

63. Geophilid

64. Centipede fangs Notes:
1) All are predators….ants are the worst predators because they work as individuals and as a colony
2) Specialist predators eat 1 or 2 species
3) Generalists eat many types of species

65. Ant head

66. Snail-feeding beetle

67. Snail-feeder, immature

68. Taracus - Opilionid
Note: Devices for butchering a snail

69. Glowworm eating millipede
Note: Glowworm catches a millipede and cuts segments off one by one and sucks insides out
Millipede segments

70. Diapriid wasp – Diptera parasite
Note: You could collect species of unnamed parasitic wasps

71. Rhododendron decomposition

72. Millipede jaws
Notes:
1)Millipedes are the big shredders in this system
2) Molars crush dead leaf-filter through sieve, grind large pieces again

73. Schematic of millipede jaw

74. Harpaphe mating swarm

75. Leaf skeletonization

76. Isopod

77. Pen-knife mite
Note: Really important shredders

78. Pen-knife mite, closed
Note: When a predator comes they totally close up in a ball and it takes an hour for a predator to crack open

79. Collohmannia nymphs

80. Leaf skeletonized by Collohmannia

81. Bacteria eaten by fungus
Note: Fungus dissolves bacteria by secreting a substance in 30 minutes

82. Soil and Plant Growth
Microbial biomass
(bacteria, fungi)
(nutrient
immobilization)
In the short-term (minutes to years) the USEFUL nutrient content of soils is basically equivalent to the amount of nutrient incorporated into living microbial tissue.
(Most nutrients in mineral soil are long-term resources)

83. Soil and Plant Growth
Microbial biomass
(bacteria, fungi)
(nutrient
immobilization)
Microbes grow by producing exoenzymes that decompose the organic (+) material in the soil
more bacteria
more decomposition

84. Soil and Plant Growth Microbial biomass plant biomass
(bacteria, fungi)
(nutrient
immobilization)
Human Connection :
Think of it this way… the reason you chew your food is to increase its surface area, which increases the nutrients the bacteria can uptake.
Your intestines grab whole bacteria, kill them and dump their remains in your bloodstream. Humans are basically bacteriavores like arthropods are.
Nutrient availability in dead/decaying organic
matter is limited by surface area for exoenzyme attack
“shredding” increases surface area; therefore shredding
animals (like millipedes) indirectly regulate rate of
decomposition and microbial growth (example: 450x)
plant biomass

85. Soil and Plant Growth ? Microbial biomass shredders
(bacteria, fungi)
(nutrient
immobilization) ?
shredders
roots are completely
passive for
nutrient uptake

86. Protozoa, Nematoda, Arthropoda
Soil and Plant Growth
Question: If we were interested in finding soil nutrients do we look at fungi/bacteria?
Microbial biomass
(bacteria, fungi)
(nutrient
immobilization)
Answer: Yes
bug poop
(nutrient
mineralization)
shredders
(surface area)
nearly all nutrients mineralized by
microbivory are assimilated by the
remaining microbes.
Protozoa, Nematoda, Arthropoda
nutrient uptake
Surface area (microbes) surface area (roots)
Positive Feedback Loop: More bacteria>>More enzymes>>More bacteria>>More enzymes
Plants only can assimilate nutrients released in the rhizophere

87. Anderson Millipede soil mineralization
Notes:
1)Took soil from oak forest, sterilized it, reconstructed soil horizons in flower pots, reinnoculated fungi, bacteria and protozoa, NO bugs.
2) Flower pot>>adds H2O>>trickles to bottom>>tests for N.
3) Then adds shredder (millipede)…LOTS more N.
4) Adds baby oak tree (No difference).
5) Repeats study and baby oak tree. No difference. Baby oak tree used N from millipede feces for growth.
6) WHOLE POINT: All of the nutrients that are ultimately incorporated in to the growing plants, have to go through the digestive system of the shredder.
7) Unless you are dumping fertilizers the only way nutrients will help plants is bug poop.
When you double the N content, the growth of the oak tree is tenfold.

88. Onion cultivation