SOIL ORGANISMS Global Soil Biodiversity Initiative website More

SOIL ORGANISMS

Global Soil Biodiversity Initiative website

More useful way to classify soil organisms for our purposes: MICROFAUNA : < 0. 1 mm (WIDTH) Bacteria, fungi, nematodes MESOFAUNA : 0. 1 – 2 mm Springtails, pseudoscorpions, dipluran MACROFAUNA : 2 – 20 mm Ants, some mites, earthworms, beetles MEGAFAUNA : > 20 mm Moles, reptiles, badgers

1. Mesofauna and Macrofauna

arthropods ¾ of all living organisms Exoskeleton, jointed legs, segmented body Insects Crustaceans Arachnids Myriapoda

Shredders Microbial taxis

Mites arachnids

Mite Facts 4 pairs legs Blind; use physical and chemical sensing to navigate 40, 000 described species Variety of food preferences (microbes, plants, some carnivorous)

Extracted from one ft 2 of top two inches of forest litter and soil

Very persistent Withstand 100 x as much radiation as humans Persist in an area after it becomes industrialized Therefore can be used to determine prior vegetation type Fossilized mite assemblages are used to reconstruct past environments

Springtails (Collembola) Arthropods Invertebrates with external skeleton Hexapods ( not insects) 6 legs Spring or hop Furca Eat fungal hyphae, spores and detritus Some predatory on mites

Can withstand freezing conditions Have been featured on a postage stamp!

Proturans Hexapods No antennae, no eyes Pale or yellowish, pointed at both ends Found in leaf litter, humus, moss, decaying wood 700 described species

Raise their back end when disturbed (like scorpions) Eat fungal hyphae, are eaten by mites, spiders pseudoscorpions

Diplurans White or colorless hexapods Some are dark Elongated body Head has pair of strings with beaded segments Confused with earwigs but have no eyes or wings Can regenerate lost

Diplurans vs. Earwigs Some have pincers Diplurans are not insects Earwigs have pincers Earwigs are insects

Live in leaf litter, wood, under rocks and logs Eat decomposing plant and animal matter; some eat nematodes and small arthropods japygid

Pseudoscorpions Arachnids Fused head and thorax; 11 -12 segments in abdomen Smaller head appendages are for feeding; larger ones for defense Molt; can live 3 -4 yrs

Live under bark, stones, in leaf litter, caves Have appeared on a postage stamp!

Carnivorous: eat larvae, ants, mites, flies

Beetles Arthropods; order Coleoptera 370, 000 described species (40% of all known insect species; 30% of all known animal species) Some omnivores, some eat plants, fungi, some are carnivores Larvae (grubs)

Hardened forewings cover body of beetles Most soil beetles are brown or black Some soil beetles are wingless

Rove beetle Largest beetle family in North America Very fast and agile, are biting Carnivorous; consume more than own weight in a day Act as good “pesticides” by eating harmful root maggot flies

Rove beetles

Featherwing beetles Smallest known beetles Wings are long and are feather-shaped Abundant on forest floor

Short-winged mold beetles Eat mold, also springtails, mites, symphylans Have beady antennae to use in the confining passages of soil Have short wing covers that do not restrict movement

Myriapoda (centipedes, millipedes, symphyla) Long, segmented bodies, lots of legs (up to 750 pairs !)

Millipedes: 2 pairs legs per segment; decompose leaf litter Centipedes: 1 pair legs per segment; have venom glands to immobilize prey; predators Symphyla: root feeders

Other Macrofauna and Mesofauna CHORDATES (vertebrates) mammals, amphibians, reptiles PLATYHELMINTHES (flatworms) ASCHELMINTHES (roundworms, nematodes) MOLLUSKS (snails, slugs) ANNELIDS (earthworms)

vertebrates Squirrels, mice, groundhogs, rabbits, chipmunks, voles, moles, prairie dogs, gophers, snakes, lizards, etc. Contribute dung and carcasses Taxicabs for microbes

nematodes

NEMATODES

Nonsegmented, blind roundworms > 20, 000 species Eat bacteria or fungi or plants (stylet) And protozoa, other nematodes, algae Specialized mouthparts Can sense temperature and chemical changes

NEMATODES Bacteria feeder Fungal feeder

Predatory Nematode

Root-feeding nematodes

nematode

Nematode Trappers Fungal hyphal rings constrict when a nematode swims through.

BACTERIA

Bacterial biomass dominates : grassland agricultural landscapes Fungal biomass dominates: Forests

bacteria

Bacteria Tiny (1 μm width), one-celled Single cell division In lab: 1 can produce 5 billion in 12 hours (In real world limited by predators, water & food availability) Abundant in rhizosphere Four FUNCTIONAL GROUPS: Decomposers Mutualists : partner with plants Pathogens Chemoautotrophs

Some terms: Autotrophs: can make organic compounds from inorganic compounds Heterotrophs: feed on others to make organic compounds Chemosynthetic: get energy from inorganic chemical reactions Photosynthetic: get energy from sun Aerobes: use aerobic respiration (need oxygen as electron acceptor) Anaerobes: use inorganic or organic compounds for electron acceptor

Decomposers Organic chemicals in big complex chains and rings Bacteria break bonds using enzymes they produce Create simpler, smaller chains

Mutualists e. g. , Nitrogen-fixing Bacteria Nodules formed where Rhizobium bacteria infected soybean roots.

Root nodules

Chemoautotrophs Get energy from OTHER THAN CARBON compounds From N, S, Fe, H

Actinomycetes Are bacteria but grow like fungi Filamentous but morphology varies Adaptable to drought Important at high p. H Usually aerobic heterotrophs Break down wide range of organic compounds Produce geosmin (smell of “fresh soil”)

other Microflora Protozoa Algae Fungi

PROTOZOA Ciliates • Largest of the three • Move by means of hair-like cilia • Eat other protozoa and bacteria Amoeba • Also large • Move by means of a temporary foot (pseudopod) Flagellates • Smallest of the three • Move by means of a few whip-like flagella.

Protozoa Flagellates Amoeba Ciliates Eat bacteria & protozoa

protozoa Unicellular Heterotrophic Eat bacteria, fungi Form symbiotic relationships e. g. , flagellates in termite guts; digest fibers Require water Go dormant within cyst in dry conditions

Function of protozoa Make nutrients plant-available Release excess N from the bacteria they eat Regulate bacteria populations Compete with pathogens

PROTOZOA Sand bacteria protozoa

Flagellate

Ciliate

Amoeba bacteria amoeba

Soil-Dwelling “Vampires” Vampyrellids Group of amoebe that drill holes in fungus and consume liquid

Archaea ( ar-KEY-ah) A recent discovery: 1970 s Woese and Fox: Divided bacteria into “normal” and “extremophiles” (archaeabacteria) Changed classic “tree of life” Bacteria Archaea Eukaryotes

Very similar to bacteria in shapes and size and reproduction Differences: Cell membranes contain lipids Not chitin (like fungi) Not cellulose (like plants) Genes of archaea are more similar to eukaryotes than to bacteria Can use a lot of various substances for energy

Importance Role in carbon cycle Photoautotrophs, chemoautotrophs, photoheterotrophs, chemoheterotrophs Many can survive in extreme environments (enzymes); heat, cold, salt, low p. H Many are methane-producers: Swamp gas, cow farts Sheer numbers: Combined marine and soil archaea make them the most abundant organism on earth

Importance in Soil Role in N cycle Ammonia oxidizers Decomposition Important anaerobic decomposers Important in extreme environments where bacteria do not fluorish

algae Filamentous, colonial, unicellular Photosynthetic Most in blue-green group, but also yellow-green, diatoms, green algae Need diffuse light in surface horizons; important in early stages of succession Form carbonic acid (weathering) Add OM to soil; bind particles Aeration Some fix nitrogen

Fungi Break down OM, esp important where bacteria are less active attack any organic residue Most are aerobic heterotrophs chemosynthetic: adsorb dissolved nutrients for energy

Grow from spores into branched hyphae Hyphal strand divided into cells by septa that allow flow of liquids between cells Masses of hyphae grow together in visible threads called mycelia

Advantages over bacteria: They can grow in length Rate: 40 μm / min (bacterium travels 6 μm in its life) Don’t need a film of water to move Can find new food sources Transport nutrients great distances Produce enzymes that break down complex compounds Can break down lignin (woody compound that binds cellulose), shells of insects, bones Can break down hard surfaces

Clever, clever adaptations! Infecting a nematode Hypha twists back on itself and catches a nematode, hyphal cells swell and kill nematode then enter body and suck out nutrients Oyster mushroom Emits toxic drops from hyphal tips which touch nematode, immobilize it and hyphae enter body and remove nutrients Trap arthropods or protozoa and digest them

Mycorrhizae: symbiotic absorbing organisms infecting plant roots, formed by some fungi normal feature of root systems, esp. trees increase nutrient availability in return for energy supply plants native to an area have well-developed relationship with mycorrhizal fungi Can extend the effective surface area of tree’s roots by 700 -1000 x

Mycorrhizae Tree root Fungal hyphae Mycorrhizal structure

Ectomycorrhizal Grow close to root surfaces Hardwoods and conifers Endomycorrhizal Penetrate and grow inside roots Vegetables, annuals, grasses, shrubs, perennials, softwoods

Ectomycorrhizae

Arbuscular Mycorrhizae (AM)

Higher fungi have basidium : club-shaped structure , bearing fruiting body toadstools, mushrooms, puffballs, bracket fungi

Fungi and Soil Quality Decompose carbon compounds Improve OM accumulation Retain nutrients in the soil Bind soil particles Food for the rest of the food web Mycorrhizal fungi Compete with plant pathogens

Earthworms (Macrofauna: > 1 cm long) ANNELIDS

earthworms Some 7000 species 3 categories: Epigeic (leaf litter/compost dwelling ) Endogeic (topsoil or subsoil dwelling ) Anecic (deep burrow drillers)

Giant Benefits to soil Move air in and out of soil Castings are rich in available nutrients Produce 10 lbs / yr

1 acre good garden soil: 2 -3 million 1 acre forest soil: 50, 000