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18 Cards in this Set
- Front
- Back
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what is the difference between R-strategists and k-strategists?
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R strategists (opportunists) break down more matter and fast, k-strategist (speciailized) break down less slower
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where does carbon from plant go once it is broken down?
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most converted to CO2, some goes to microbial biomass which becomes humus
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what are the factors that affect decomposition rates?
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surface area of substrate
degree of soil contact composition (resistent or not) availablity of inorganic nutrients enviromental conditions |
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of hemicellulose, cellulose and lignin, how much will be left after 300 days?
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hemicellulose is gone, 15% cellulose, 50% lignin
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what is the median carbon nitrogen ratio?
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25/1
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when does a net mineralization of N occur?
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when there is a low c/n ratio
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when does a net immobilization of N occur?
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when there is a high c/n ratio (not enough N)
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what is the c/n ratio of humus?
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about 10/1
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what is the c/n ratio of the o horizon?
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above 25 c/n
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what is the c/n ratio of other horizons (not o horizon)?
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below 25 c/n
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how is 100g of organic carbon in residues distributed after 1 year in soil?
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more than 2/3 oxidized to CO2, less that 1/3 remains in soil (most in soil humus, some in cells of soil organisms)
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what is an example of why some humic substance are bad for plant growth?
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allelopathy (black walnut)
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what is allelopathy?
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production of compounds by plants which inhibit the growth of other plants
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what is the chemical produced by the black walnut tree?
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hydrojuglone
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which soil class has the greatest depth of organic matter?
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mollisols
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which soil class has a bulge in organic matter about 30 cm deep?
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spodosols
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soils high in what tend to have high levels of organic carbon?
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silt and clay
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what happens when crops such as corn and soybeans are used for biofuel?
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in soil, organic matter goes down, bulk density goes up
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