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THE SOIL FOOD WEB. Soil Biology and the Landscape.

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Presentation on theme: "THE SOIL FOOD WEB. Soil Biology and the Landscape."— Presentation transcript:


2 Soil Biology and the Landscape

3 The Soil Food Web

4 Components of Soil Organic Matter Decomposing organic matter (active fraction) 33% - 50% Stabilized organic matter (humus) 33% - 50% Fresh residue <10% Living organisms <5%

5 Rhizosphere

6 Microbial Biomass with Depth

7 Seasonal Microbial Activity


9 Biomass of Soil Organisms in Four Ecosystems

10 Typical Numbers of Soil Organisms in Healthy Ecosystems Ag LandPrairieForest Organisms per gram (teaspoon) of soil Bacteria100 mil. -1 bil. FungiSeveral yards10s – 100’s of yds1-40 miles (in conifers) Protozoa1000’s 100,000’s Nematodes10-2010’s – 100’s100’s Organisms per square foot Arthropods< 100500-200010,000-25,000 Earthworms5-3010-50 (0 in conifers)

11 Methods for Measuring the Food Web Counting Direct counts of individuals Plate counts of colonies Activity levels Respiration (CO 2 production) Nitrification rates Decomposition rates Cellular constituents Biomass C, N, or P Enzymes Phospholipids DNA and RNA

12 Bacteria with fluorescent stain for counting

13 A Complex Food Web

14 Complexity of the Soil Food Web in Several Ecosystems

15 Two Bugs are Better Than One Effects of bacteria and bacterial-feeding nematodes on blue grama grass growth


17 Nitrogen-fixing Bacteria Nodules formed where Rhizobium bacteria infected soybean roots.

18 Actinomycetes Bacterial cells Grow like fungal hyphae


20 Fungi and Soil Quality Decompose carbon compounds Improve OM accumulation Retain nutrients in the soil Bind soil particles Food for the rest of the food web Mycorrhizal fungi Compete with plant pathogens

21 Mycorrhizae Tree root Mycorrhizal structure Fungal hyphae

22 Ectomycorrhizae

23 Arbuscular Mycorrhizae (AM)

24 Mushrooms: The fruiting body of some fungi

25 Mycorrhizal Fungi

26 PROTOZOA Ciliates Largest of the three Move by means of hair-like cilia Eat the other protozoa and bacteria Amoebae Also large Move by means of a temporary foot (pseudopod) Include testate amoebae (with shell-like covering), and naked amoebae Flagellates Smallest of the three Move by means of a few ship-like flagella.


28 Flagellate

29 Ciliate

30 Mineralization and Immobilization Organisms consume other organisms and excrete inorganic wastes. Inorganic nutrients are usable by plants, and are mobile in soil. Organic nutrients are stored in soil organisms and organic matter. Organisms take up and retain nutrients as they grow.

31 Soil-Dwelling “Vampires”



34 Predatory Nematode

35 Root-feeding nematodes

36 Nematode Trappers Fungal hyphal rings constrict when a nematode swims through.


38 Mites and Biodiversity

39 Types of Arthropods Shredders Predators Herbivores Fungal-feeders

40 Shredders

41 Predators (1)

42 Predators (2): Centipedes

43 Herbivores

44 Springtails (fungal feeders) Abundant in many soils. Feed on some disease-causing fungi. Jump by slamming their tail down.

45 What is in Your Soil? Berlese funnel Pitfall trap


47 Earthworms bury litter

48 Earthworm burrow

49 Vertical burrows

50 Earthworm casts

51 Earthworm burrow opening

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