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  1. LECTURE 6 SOIL INVERTEBRATES Reading: Coleman et al. (text) – Chapters 4, (6 and 7) Moldenke et al. 2000 Bohlen et al. 2004 Fender 1995

  2. Soil organisms

  3. Soil Invertebrate Lecture Topics 1. Diversity of soil arthropods 2. Functional Feeding Groups: shredders, grazers, predators, parasites, mutualists fungivores, bacteriovores, detritovores 3. Functional Roles in ecosystems decomposition and nutrient cycling 4. Energetics & Trophic Interactions in soil food webs invertebrates and microbes 5. Effect of exotic earthworms on forest ecosystems

  4. 1. Diversity of soil Invertebrates

  5. Litter and soil mites Described - 20,000 – 30,000 spp. Estimated - 70,000 - 600,000spp Soil and litter insects estimated at about 1/3 of total.

  6. INVERTEBRATES Common Phyla in soil Protozoa Mollusca - slugs and snails Annelida - earthworms, enchytraeid worms, leeches Nematoda - nematodes (round worms) Platyhelminths - flat worms Arthropoda - crustacea - isopods (pill bugs) - arachnida - spiders, pseudoscorpions, mites (Acari) - myriopoda - centipedes (Chilopoda), millipedes (Diplopoda) - insecta - springtails (Collembola), termites (Isoptera), beetles (Coleoptera), flies (Diptera), ants

  7. Major groups of Soil Fauna The Micofauna < 0.1 mm Nematodes or roundworms Protozoa

  8. Major groups of Soil Fauna The Mesofauna 0.1 - 2 mm Mites Featherwing beetle Springtails Protura Pseudoscorpions Diplura

  9. Mites Prostigmata Mesostigmata Oribatid (Dave Walter)

  10. Mites and Collembola comprise >90% of soil invertebrate density (no/m3) in old-growth forest in the Hoh River Valley

  11. Enchytraeid worms

  12. Major groups of soil Fauna The Macrofauna > 2 mm Earthworms Millipedes Ants Termites Ground beetles Isopods

  13. Carpenter Ants

  14. Leaf Cutter Ants: Atta spp.

  15. TERMITES – IMPORTANT IN THE TROPICS

  16. Native earthworms in forest soil from coastal Oregon

  17. Soil Invertebrates: Comparison of TemperateForests Forest Type Coniferous Deciduous Biomass (dry weight mg/m2) Collembola 80 110 Oribatid Mites400-1000100-400 Earthworms 450 5300 Total 2400 8000 Density (no. x 103/m2) Collembola 145-244 40-70 Oribatid Mites100-300 20-50 Earthworms 0.005-1.1 0.1-1.3 (Shaw et al. 1991)

  18. 2. Functional Feeding Groups

  19. SOIL INVERTEBRATE TROPHIC STRUCTURE OF 4 CONIFER SITES IN WESTERN OREGON (relative numerical abundance) Willamette Valley Metolius River 8% 23% 37% 8% fungivore detritivore bacteriovore 60% predators 63% 8% Coast Waldo Lake 3% 5% 5% 16% 73% (Moldenke and Marra 1987 unpublished data) 90%

  20. 3. Functional Roles of Soil Invertebrates

  21. Roles of Soil Invertebrates Dead Organic Matter Microbes Invertebrates 1) Increase decomposition rates 2) Fragment litter and channel wood and soil 3) Transport microbes and inoculate substrates 4) Graze on microbes and release nutrients 5) Ecosystem engineers – mix substrates

  22. From Moldenke et al. 2000

  23. 4. Trophic Levels and Energetics

  24. Heterotrophic Respiration Invertebrates 10% Decomposers 95% Microbes Bacteria & Fungi Net Primary 90% Production Herbivores 5% ( Richle 1981)

  25. 5. Effects of exotic earthworms on ecosystems

  26. Epigeic – feed on surface organic matter From Bohlen et al. 2004 Hypogeic - mix mineral and organic layers Anecic – live in vertical burrows – move mineral soil up. e.g., Lumbricus terrestris

  27. From Bohlen et al. 2004