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28 Cards in this Set
- Front
- Back
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Nematodes |
Most numerous macro fauna up to 90% of multicellular animals in soil. |
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Macro fauna |
Nematodes, mites and springtails most live in surface or litter layers |
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Algae |
Auto trophic, surface to a few mm into soil pores. |
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Micro organisms |
Algae, fungi, bacteria |
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Fungi |
Hetero trophic hyphae , helps aggregate, multicellular. Yeast is unicellular. Some associated with plants, |
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Bacteria |
Most abundant soil organisms. Hetero and auto trophic; anaerobic. Mostly in cohesion. |
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Nitrification |
NH4 -O2-> NO3 |
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Actinomycetes |
Group of bacteria with a superficial resemblance to fungi. More competitive for very resistant OM (humus and lignin) |
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Constraints |
Physical, chemical, nutritional |
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Physical constraints |
Space, H20 (field capacity-permanent wilting point), temperature (sub freezing to 45C, seasonal), O2 deficiency (H2O saturation) |
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Chemical constraints |
pH, salinity |
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Nutritional constraints |
Nitrogen (stored in the soil OM decomposition, tremendous competition for NH4 and NO3 in soil water) carbon, |
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Adaptations to deal with constraints |
Autotrophy, opportunism, inhibitor production, specialise, parasitism and predation, symbiosis, |
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Autotrophy |
Photosynthesis- algae (blue-green), bacteria, chemo autotrophs |
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Opportunism |
Add OM, increased biological activity |
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Inhibitor production |
Antibiotics |
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Specialise |
Anaerobic bacteria- decompose wood enzyme production to decompose resistant OM, handle drought |
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Symbiosis (Constraint resistance adaptations) |
N2 fixation- mycorrhizae, legumes |
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Associations of microorganisms with plants |
Rhizosphere organisms, root pathogens and parasites, and symbiosis. |
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Rhizosphere Organisms |
Roots provide a surface organic substrates O2 Area of extensive biological activity ->microbes |
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Root Pathogens and Parasites |
Damping off, root rot, wilt diseases Parasitic nematodes |
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Symbioses (Microorganism and plant association) |
Nitrogen fixing (bacteria) Mycorrhizae or mycorrhizas (fungi) phosphate and zinc |
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Nitrogen Fixing Symbiosis |
- Blue-green bacteria - Frankia spp. - Rhizobium and Bradyrhizobium spp.
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Blue-green bacteria |
photosynthetic, colonize specialized cavities in shoot systems of certain cycads and ferns. Provides an enclosed aquatic system including inorganic nutrients. ex: Anabaena (bacteria) and Azolla (floating fern) used in east Asia to provide N2 for rice |
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Frankia spp. |
actinomycetes infect roots of shrubs and trees forming N2 fixing root nodules similar to Rhizobium-legume symbiosis ex: Desert and brushland shrubs - Ceanothus (deerbrush) and Purshia (bitterbrush) Trees - Myrica (myrtle), Alnus (alder) and Casuarina. |
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Rhizobium and Bradyrhizobium spp. |
(rhizobia) bacteria that infect root plants of the legume family, forming N2 fixing root nodules. used for centuries in agriculture to get N2 directly into valuable high- protein foods and indirectly into momlegume crops via soil residue incorportaion ex: alfalfa, clover, pea, soybean, lentil, chickpea, and lotus |
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Azotobacteria and Clostridium |
Free living bacteria that fix atmospheric N2 Azotobacteria - aerobic Clostridium - anaerobic |
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Mycorrhizae |
fungi (provides inorganic nutrients) and plant roots (provides carbon compounds) Ectomycorrhizae - in woody plants between cells endomycorrhizae - annual, herbaceous, maples, inside cortical cells |
