Dr. Andrew MoldenkeDept. of Botany

Oregon State University

Special thanks to Dr. Moldenke for presentation notes provided during the 2009 HJ Andrews LTER summer workshop.

Three thin-sectioned soils

Note: Really large dark blobs are earthworm poop

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: 70-80% of all arthropod species in the world live in the soil (terrestrial ecosystems)

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

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. 

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…

• 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

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

Creatures that live in the soil are very sensitive to abiotic and biotic factorstherefore excellent for use as biological indicators.

They have fantastic potential as indicators for determining human impacts on soil ecosystem function and for soil health.

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.

Indicators of change in the productive potential of soil is great but I want to talk about 2 other things today.

1. 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.

Many mites

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 (Andy’s foot)

15,000 species in Oregon

So, who cares?

Why study bugs in soil?

What do they do?

they eat and they poop

1 2

Question: Which bugs are discussed here?Answer: Mites, springtails, and other arthropods

OdontodamaeusMites….

OppiellaMites….

EpidamaeusMites….

Long-legged near DamaeusMites….

Galumna openMites….

Galumna closedMites….

Note: Defense mechanismsHands and legs fold in and doors close in

PterochthoniusMites….

HermanniellaMites….

Rearing mites

Small/large turtle mites

Note: Turtle mites are smaller than an eyelash

Oribatid cheliceraeMites….

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

Mycorrhiza under the Electron Microscope

IsotomaSpringtails…

Notes: If attacked, the tail drops and launches the bug easily a meter.

Springtails deep in the soil are blind.

Diagrammatic springtail (Collembola)

OnychiurusSpringtails…

Onychiurus

Onychiurus, high magnification

Ptiliid beetle

forewingNote: Flight apparatus is like a bird feather. ( A little rod with hairs). 

Other arthropods…

ProturaOther 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 

  

EnchytraeidOther arthropods…

Suctobelbella – bacterial-feeder

Other arthropods…

Cydnidae – Burrowing bugOther arthropods…

SymphylaOther arthropods…

Cicindelid immatureOther arthropods…

GamasidOther arthropods…

UropodidOther arthropods…

Uropodid - facial view

PolyaspididOther arthropods…

Note: Strings of wax secreted from the analogous of sweat glands

CytaMites…

Notes:

1)Predacious mite

2) Dumped out of helicopters on caterpillars (bio- control) 

Onychiurus being eaten by Labidostoma

Symphylan being eaten by Pergamasus

Note: Worst vegetative pest in the Williamette Valley

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)

Pseudoscorpion

Note: Poison gland in tip of claw released on prey

Chthoniid pseudoscorpion

Pseudoscorpion, facial view

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 

Sclerobunus – skunk-spider

Native scorpion with young

Spider webs

Spider fangs

Callobius

Pardosa

Micro-spider, male

Antrodiaetus

OmusCicindela

Staphylinidae

Lithobiidae

Geophilid

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

Ant head

Snail-feeding beetle

Snail-feeder, immature

Taracus - Opilionid

Note: Devices for butchering a snail 

Glowworm eating millipede

Millipede segments

Note: Glowworm catches a millipede and cuts segments off one by one and sucks insides out

Diapriid wasp – Diptera parasite

Note: You could collect 50-100 species of unnamed parasitic wasps

Rhododendron decomposition

Millipede jaws

Notes:

1)Millipedes are the big shredders in this system

2) Molars crush dead leaf-filter through sieve, grind large pieces again

Schematic of millipede jaw

Harpaphe mating swarm

Leaf skeletonization

Isopod

Pen-knife mite

Note: Really important shredders

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

Collohmannia nymphs

Leaf skeletonized by Collohmannia

Bacteria eaten by fungus

Note: Fungus dissolves bacteria by secreting a substance in 30 minutes

Soil and Plant Growth

Microbial biomass(bacteria, fungi)

(nutrientimmobilization)

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)

Soil and Plant Growth

Microbial biomass(bacteria, fungi)

(nutrientimmobilization)

Microbes grow by producing exoenzymes that decompose the organic (+) material in the soil

more bacteria

more decomposition

Soil and Plant Growth

Microbial biomass(bacteria, fungi)

(nutrientimmobilization)

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

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.

Soil and Plant Growth

Microbial biomass(bacteria, fungi)

(nutrientimmobilization)

roots are completelypassive for

nutrient uptake

shredders ?

Soil and Plant Growth

Microbial biomass(bacteria, fungi)

(nutrientimmobilization)

nutrient uptake

shredders(surface area)

bug poop(nutrient

mineralization)

nearly all nutrients mineralized bymicrobivory are assimilated by theremaining microbes.

Surface area (microbes) surface area (roots)

Plants only can assimilate nutrients released in the rhizophere

Protozoa, Nematoda, Arthropoda

Question: If we were interested in finding soil nutrients do we look at fungi/bacteria?

Answer: Yes

Positive Feedback Loop: More bacteria>>More enzymes>>More bacteria>>More enzymes

Anderson Millipede soil mineralizationNotes:

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.

Onion cultivation