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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.
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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. A
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.
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 • Thread-like hyphae; some form visible fruiting bodies (mushrooms, bracket fungi) • Up to 50 meters/g • Decomposers, plant symbionts, pathogens, predators
Protozoa • Single-celled animals • 10,000 - 100,000/g • Feed on bacteria, fungi, decaying organic matter, other protozoa
Nematodes • 1 - 4.5 mm • Up to 7 million /m2 • 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 • 1 - 7 mm • Up to 100,000/m2 • Fungus feeders, decaying OM, some plant feeders
Mites • 0.1 - 3mm • Up to 250,000/m2 • Decomposers, predators, parasites, plant feeders
Earthworms • 2 - 20 cm • 10 - 950/m2 • 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