Soil Critter Talk

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

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All that information (and more!) simply in a list
of the relative abundance of the species
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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.
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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.
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• 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 dont just passively indicate soil
  health they are key players in the cycle of
  plant growth and soil nutrients themselves.
• B.P.G.T.

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Many mites
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EACH and EVERY SHOVEL of forest dirt all
pictures that follow 250 spp/m2 350,000
indivs/m2 70-80 of all arthropods in
most terrestrial ecosystems 120,000 little
legs (Andys foot) 15,000
species in Oregon
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So, who cares? Why study bugs in soil?
What do they do? they eat and
they poop
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Question Which bugs are discussed here? Answer
Mites, springtails, and other arthropods
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Odontodamaeus
Mites.
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Oppiella
Mites.
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Epidamaeus
Mites.
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Long-legged near Damaeus
Mites.
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Galumna open
Mites.
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Galumna closed
Mites.
Note Defense mechanisms Hands and legs fold in
and doors close in
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Pterochthonius
Mites.
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Hermanniella
Mites.
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Rearing mites
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Small/large turtle mites
Note Turtle mites are smaller than an eyelash
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Oribatid chelicerae
Mites.
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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
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Mycorrhiza under the Electron Microscope
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Isotoma
Springtails
Notes If attacked, the tail drops and launches
the bug easily a meter. Springtails deep in
the soil are blind.
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Diagrammatic springtail (Collembola)
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Onychiurus
Springtails
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Onychiurus
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Onychiurus, high magnification
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Ptiliid beetle
Other arthropods
Note Flight apparatus is like a bird feather. (
A little rod with hairs).  
forewing
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Protura
Other arthropods
  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      
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Enchytraeid
Other arthropods
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Suctobelbella bacterial-feeder
Other arthropods
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Cydnidae Burrowing bug
Other arthropods
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Symphyla
Other arthropods
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(No Transcript)
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Cicindelid immature
Other arthropods
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Gamasid
Other arthropods
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Uropodid
Other arthropods
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Uropodid - facial view
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Polyaspidid
Other arthropods
Note Strings of wax secreted from the analogous
of sweat glands
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Cyta
Mites
Notes 1)Predacious mite 2) Dumped out of
helicopters on caterpillars (bio- control)  
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Onychiurus being eaten by Labidostoma
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Symphylan being eaten by Pergamasus
Note Worst vegetative pest in the Williamette
Valley
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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)
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Pseudoscorpion
Note Poison gland in tip of claw released on
prey
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Chthoniid pseudoscorpion
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Pseudoscorpion, facial view
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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  
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Sclerobunus skunk-spider
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Native scorpion with young
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Spider webs
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Spider fangs
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Callobius
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Pardosa
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Micro-spider, male
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Antrodiaetus
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Omus
Cicindela
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Staphylinidae
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Lithobiidae
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Geophilid
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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
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Ant head
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Snail-feeding beetle
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Snail-feeder, immature
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Taracus - Opilionid
Note Devices for butchering a snail  
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Glowworm eating millipede
Note Glowworm catches a millipede and cuts
segments off one by one and sucks insides out
Millipede segments
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Diapriid wasp Diptera parasite
Note You could collect 50-100 species of unnamed
parasitic wasps
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Rhododendron decomposition
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Millipede jaws
Notes 1)Millipedes are the big shredders in
this system 2) Molars crush dead leaf-filter
through sieve, grind large pieces again
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Schematic of millipede jaw
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Harpaphe mating swarm
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Leaf skeletonization
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Isopod
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Pen-knife mite
Note Really important shredders
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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
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Collohmannia nymphs
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Leaf skeletonized by Collohmannia
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Bacteria eaten by fungus
Note Fungus dissolves bacteria by secreting a
substance in 30 minutes
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Soil and Plant Growth
Microbial biomass (bacteria, fungi) (nutrient immo
bilization)
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)
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Soil and Plant Growth
Microbial biomass (bacteria, fungi) (nutrient immo
bilization)
Microbes grow by producing exoenzymes that
decompose the organic () material in the soil
more bacteria
more decomposition
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Soil and Plant Growth
Microbial biomass (bacteria, fungi) (nutrient immo
bilization)
?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
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Soil and Plant Growth
Microbial biomass (bacteria, fungi) (nutrient immo
bilization)
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shredders
roots are completely passive for nutrient uptake
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Soil and Plant Growth
Question If we were interested in finding soil
nutrients do we look at fungi/bacteria?
Microbial biomass (bacteria, fungi) (nutrient immo
bilization)
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 bacteriagtgtMore
enzymesgtgtMore bacteriagtgtMore enzymes
Plants only can assimilate nutrients released in
the rhizophere
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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 potgtgtadds H2Ogtgttrickles to
bottomgtgttests 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.
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Onion cultivation