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Soil Biology

Soil Biology. Who is down there and what do they do. Learning Objectives. List the major groups of soil organisms … Identify the roles of organisms Draw a simplified soil food web . .. Describe the conditions affecting growth… Discuss the beneficial functions …. air. water. soil. Sun.

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Soil Biology

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  1. Soil Biology Who is down there and what do they do

  2. Learning Objectives • List the major groups of soil organisms … • Identify the roles of organisms • Draw a simplified soil food web . .. • Describe the conditions affecting growth… • Discuss the beneficial functions …

  3. air water soil Sun Producers Decomposers Consumers Humus

  4. Important Groups of Soil Organisms Size/type class e.g. and functional group/energy acquisition Vascular plants, mosses • Macroflora • Microflora • Macrofauna Vascular plants, algae, actinomycetes, bacteria, and fungi** ** Fungi are actually their own separate kingdom Vertebrates, arthropods, earthworms, snails… • Mesofauna • Microfauna Bigger arthropods, worms Nematodes, protazoa

  5. Soil Animals – micro, meso, macro

  6. Microflora Bacteria

  7. Microflora

  8. Nematodes Microfauna Protozoa 20-200 kg/ha!

  9. Mites Mesofauna Springtails

  10. Other invertebrates Mesofauna

  11. Worms Voles! Macrofauna

  12. A cup of soil contains... Bacteria Fungi* Protozoa Nematodes Arthropods Earthworms 200 billion { Microflora, or “microbes” 100,000 meters 20 million { microfauna 100,000 50,000 { macro- and mesofauna * Fungi are actually their own separate kingdom <1

  13. B – Bacteria A – Actinomycetes My – Mycorrhizae H – Saprophitic fungus N – Nematode CP – Ciliate protozoa FP – Flagellate protozoa M – Mite < 1mm 1/10 mm

  14. Fungi – tens of thousands of species • The major agent of decay in acid environs • Network of hyphae: improves soil structure • Decomposition of cellulose!!! • Can compete with higher plants for N • Gain energy from nematodes • 3 groups, yeast, mold, mushrooms • symbiotic relationships with most plants • Produce chemicals that are toxic

  15. Aggregates held together by: Fungal hyphae Bacterial “glues” Organic matter hyphae clay sand silt bacteria

  16. Bacteria – 1 billion -1 trillion/g soil (up to 20,000 spp.) • Exist in both forest and grassland soils • Most do best under high Ca2+, high pH • Do best when soil temp 20-40C (68-100F) but seldom killed by temp extremes

  17. Fungi vs. bacteria Single-celled, can form colonies Tube-like body; hyphae Rapid regeneration time (hours); can respond quickly to nutrient additions Generally slower growth rate

  18. Complex, mutually beneficial relationships bacteria fungi

  19. Microfauna Amoebae Ciliate • some parasitic • feed on bacteria and fungi • release plant nutrients – protozoa KEY for N Flagellate Nematode

  20. Microfauna • Nematodes(non-segmented, round worms) • Widely distributed in forest soils • Saprophytic and parasitic groups • Some predatory species attack tree roots and cause damage sap·ro·phyte An organism, that grows on and derives its nourishment from dead or decaying organic matter.

  21. Microfauna • Protozoa • Most abundant of all soil fauna • One-celled • Feed on bacteria • Up to 30% of all mineralized N from protozoa

  22. Mesofauna Collembola (springtails) Fungus feeding mite Nematode feeding mite • heterotrophs (detritivores, predators) • feed on fungi, protozoa, nematodes, mites • important in regulating populations of everything smaller

  23. Macrofauna • shred plant material • feed on bacteria and fungi associated with organic matter Photo by Suzanne Paisley

  24. Earthworm midden

  25. Earthworms – (have gizzards!) • Probably the most important component of soil fauna (not in acid soils, not in very dry soils) • Eat OM & pass as much as 30 tons/ha of soil through their bodies (mixing horizons) each year • Promote good soil structure and aeration Great for fishing! Worm farming - Huge industry! est. wt. of worms in U.S. = 10X wt. of entire human population

  26. air water soil Sun Producers Decomposers Consumers Humus

  27. Some generalizations . . . • Forested soils more biologically diverse • Forested soils dominated by fungi • Faunal biomass (and activity) greater per ha in grasslands • Cultivated soils least diverse, less biomass, fewer organisms

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