om_decomposition

Table of Contents

Select a slide or start at the beginning.

• X. Organic Matter Decomposition
  
• A. Carbon Nutrition
  
• 1. Heterotrophic soil organisms
  
• 1. Heterotrophic Reactions
  
• b) Anaerobic Respiration -
  
• c) Fermentation -
  
• Other examples -
  
• 2. Autotrophic soil organisms
  
• 2. Autotrophic Reactions -
  
• B. Assimilation
  
• Add 100 g of sugar (50% C) to medium - 50 gm
  
• (Untitled)
  
• 2. Ecological significance of assimilation efficiency
  
• C. Mineralization/Immobilization
  
• D. Decomposition of Soil Organic Matter
  
• 1. Steady State System -
  
• What factors limit microbial activity under “steady state” soil conditions?
  
• a. Soil O.M. levels (pools) in a steady state system
  
• 2) O.M./ carbon losses -
  
• b) Carbon losses by leaching
  
• c) Carbon/O.M. losses from fire
  
• b. Management activities:
  
• Example - If soil is affected by timber harvesting,
  
• 2. Decomposition of Added Organic Matter
  
• a. % Nitrogen
  
• Examples -
  
• Above 1.5 % N
  
• Immobilized N will eventually become available to plants
  
• b. C:N Ratio
  
• e.g. 100g of grass has 50 gm of C
  
• As O.M. is decomposed,
  
• Example:
  
• (Untitled)
  
• When these fungal cells die
  
• At C:N of 10:1
  
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• c. Immobilization of soil N
  
• Practical significance -
  
• d. Effect of C substrate
  
• e. Microbial Populations
  
• The type and composition of O.M. greatly affects the composition of soil microflora:
  
• E. Humus Formation
  
• Once humus formed and incorporated into mineral soil,
  
• F. Methods of Measurement
  
• 1. “Steady state” conditions
  
• Problems with this method?
  
• b. CO2 Evolution
  
• (Untitled)
  
• Sources of CO2
  
• Methods of CO2 measurement
  
• d) CO2 absorption -
  
• 2. Added Organic Matter
  
• Size of mesh bag
  
• Problems with method?
  
• 2) Brian Titus popsicle sticks
  
• b. Substrate Change
  
• c. Changes in OM physical properties
  
• (Untitled)
  
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• Take pictures of cloth in lab
  
• (Untitled)
  
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• Example from a wetland soil
  
• 2) Wood stake strength
  
• (Untitled)
  
• 4. Microbial Populations
  
• 4. Microbial Biomass
  
• b. Chloroform fumigation
  
• Soluble carbon can measured in several ways: