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Land, then, is not merely soil; it is a foundation of energy flowing through a circuit of soils, plants and animals. Aldo Leopold

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Soil is the hidden, secret friend, which is the root domain of lively darkness and silence Francis Hole Soil by parts: 5% organic, 50% space, 45% mineral

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Living, dead, decomposing, decomposed

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85% 5% 10%

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What is special about Organic compounds? They have ENERGY Food chain passes energy along through photosynthesis and respiration

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Photosynthesis: CO 2 + H 2 O + solar energy C 6 H 12 O 6 + O 2 organic !

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Respiration: C 6 H 12 O 6 + O 2 ENERGY + CO 2 + H 2 O

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Energy is passed from one trophic level to the next.

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What is an organic compound? Bank of energy

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More living biomass below ground than above! Beneath 1 acre: equivalent to 12 horses 1 cubic meter of soil: 50,000 earthworms 50,000 insects and mites 12 million roundworms 1 pea-size bit of soil: 30,000 protozoa 50,000 algae 400,000 fungi Billions of bacteria

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Springtails Beetles pseudoscorpion earthworms nematodes mites actinomycetes: geosmin, antibiotics bacteria fungi

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Arthropods Invertebrates with external skeleton Spring or hop Detrivores 100,000 / m 3 topsoil

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Arthropods; order Coleoptera 400,000 species (40% of all known insect species) Some omnivores, some eat plants, fungi, some are carnivores Larvae (grubs)

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Arachnid Joint-legged invertebrate Carnivorous: eat larvae, ants, mites, flies

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Annelids Some 2700 different types 3 categories: Epigeic (leaf litter/compost dwelling ) Endogeic (topsoil or subsoil dwelling ) Anecic (deep burrow drillers)

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

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Roundworms Occupy many positions in soil food web > 28,000 species Most microscopic Can be predatory or parasitic

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arachnids

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

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Abundant; most important decomposers Adaptable Specialized: Non-photosynthetic Photosynthetic Oxidize ammonium, nitrite, iron, manganese Oxidize sulfur Nitrogen-fixing Aerobic, anaerobic

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1 ton / acre

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Bacteria and fungal hyphae

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Break down OM, esp important where bacteria are less active branched hyphae form mycelium: bears spores attack any organic residue

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Mycorrhizae: s Symbiotic ; 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

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

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Filamentous morphology varies adaptable to drought neutral pH usually aerobic heterotrophs break down wide range of organic compounds

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A respiration process: Organic matter + O2

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Energy for decomposers CO2 + H2O Nutrients, that were in the original organic tissue, for plants Carbon, nitrogen, etc. for the decomposers HUMUS !

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Ultimate decay product of decomposition Amorphous, colloidal mixture of complex organic substances, not identifiable as tissue.

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< 0.00001 mm in diameter Nutrients and water attach to surface area of soil particles Smaller the particle, the greater the surface area per unit volume

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Sand 0.05 2.0 mm Silt 0.05 0.002 Clay