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Soil Biology (Nematodes (Functions (Bacterial feeders, Fungal feeders,…
Soil Biology
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Microbes
Importance
Fertility
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Mycorrhizae
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Endomycorrhizae, Ectomycorrhizae
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Population Dynamics
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Despite the large numbers of organisms in soil, at any one time, most of them are not active
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The majority of organisms are heterotrophic, and their growth and activity is generally limited by the low levels of available C substrates - dormant , waiting for nutrients
In favourable conditions, microbial growth rate follows exponential growth curve in response to added substrate
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Growth factors
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Water Stress
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Affects nutrient supply, mobility and leaching of organics
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Temperature
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Thermophilic, mesophilic, psychrophilic
Above optimum temp, denaturing of cellular proteins and membranes may occur
Increasing temp by 10C doubles growth rate, up to optimum (30 - 35C)
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Types
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Fungi
Up to 70% microbial biomass, 10^4-10^6/g soil
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Actinomycetes
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Degrade a wide range of molecular weight organic matter including recalcitrant materials e.g lignin and cellulose
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Algae
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Autotrophic - not decomposers, dependent on photosynthesis
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Protozoa
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Unicellular animals 10-50 um, up to 0.5mm
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Organisms grazed on depend on size (whether protozoa fit into pore in which bacteria exist) but mainly bacteria and other protozoa
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