THE LIVING SOIL

Functions of soil Support plant growth Regulate water flow Absorb and transform pollutants Habitat for living organisms  Soil Quality

Objective : Soil organisms: Who are they and what do they do? How do they contribute to soil quality?

VEGETATION Vegetation - Additon of Organic Matter (OM). Prairie ~ OM added to upper 2 ft. of soil due to fibrous root system of grass plants. Ap A AB Bg

VEGETATION Forest ~ OM added to upper 4 “ due to yearly leaf fall to surface of soil.

Prairie - Border Biotic Factor Prairie - Border soils (oak savannahs) have the influence of the prairie and forest ~ due to changes in vegetation over the past 8000 years the soils have been both under prairie and forest.

Soil Organisms: sizes and abundances

Size classification of soil fauna Microfauna (<0.1mm diameter) –Occupy water films and existing water-filled pores Protozoa, nematodes

Mesofauna (0.1 – 2mm diameter) –Occupy existing water- and air-filled pore spaces –Able to break free from surface tension of soil water Potworms, microarthropods

Macrofauna (2-20mm diameter) –Able to alter soil structure Earthworms, macroarthropods

Bacteria Microscopic, single-celled Up to 3 billion/g Autotrophs, decomposers, plant symbionts, pathogens

Fungi Up to 50 meters/g Decomposers, plant symbionts, pathogens, predators Thread-like hyphae; some form visible fruiting bodies (mushrooms, bracket fungi)

Protozoa Single-celled animals 10, ,000/g Feed on bacteria, fungi, decaying organic matter, other protozoa

Nematodes mm Up to 7 million /m 2 Bacteria feeders, fungus feeders, predators, plant roots, parasites

Isopods Crustaceans Feed on decaying plant residues

Myriapods Centipedes – predators Millipedes – decaying plant residues Symphylans, pauropods

Springtails mm Up to 100,000/m 2 Fungus feeders, decaying OM, some plant feeders

Mites mm Up to 250,000/m 2 Decomposers, predators, parasites, plant feeders

Earthworms cm /m 2 Many introduced species Decaying organic matter Different ecological types

Anecic Earthworms Medium to large size Dorsal, anterior pigment Permanent vertical burrows Forage for plant residues on the soil surface e.g. Lumbricus terrestris

Endogeic Earthworms Small to medium size Unpigmented Horizontal burrows in topsoil Feed on dead plant roots and other buried organic matter e.g. Octolasion tyrtaeum

Epigeic Earthworms Small in size Red-brown pigment Weak burrowers; do not inhabit mineral soils Forest litter, compost e.g. Eisenia fetida

Role in Soil Processes Soil formation and soil structuring Nutrient recycling and retention Population regulation

Role in Soil Formation Fragment and humify organic residues and mix into mineral soil

Soil formation Formation and stabilization of aggregates Formation of pore spaces

Nutrient Availability Symbiotic associations –Rhizobium and legumes –Mycorrhizae and most plants

Nutrient Availability Nutrient mineralization from organic matter pools Biological nutrient pool

Population regulation