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.

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

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 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 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.

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. 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

Question: Which bugs are discussed here? 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

Odontodamaeus Mites….

Oppiella Mites….

Mites…. Epidamaeus

Long-legged near Damaeus Mites….

Galumna open Mites….

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

Pterochthonius Mites….

Hermanniella Mites….

Rearing mites

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

Oribatid chelicerae Mites….

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

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

Diagrammatic springtail (Collembola)

Springtails… Onychiurus

Onychiurus

Onychiurus, high magnification

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

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

Enchytraeid Other arthropods…

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

Cydnidae – Burrowing bug Other arthropods…

Symphyla Other arthropods…

Cicindelid immature Other arthropods…

Gamasid Other arthropods…

Uropodid Other arthropods…

Uropodid - facial view

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

Cyta Mites… 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

Cicindela Omus

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

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) (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)

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

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

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

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

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.

Onion cultivation