Module 1 Flashcards
What is microbial biomass
Microbial biomass (bacteria and fungi) is a measure of the mass of the living component of soil organic matter. The microbial biomass decompose plant and animal residues and soil organic matter to release carbon dioxide and plant available nutrients.
What is organic matter content
Soil organic matter is the organic matter component of soil, consisting of plant and animal detritus at various stages of decomposition, cells and tissues of soil microbes, and substances that soil microbes synthesize.
What is oven dried weight
Remaining weight of a soil once moisture and OM have been accounted for.
List the basics of soil genesis
Soil genesis is a function of climate, organisms, relief, parent material, and time
Where are soil bacteria found
Attached to surface of soil particles, few are found free in soil solution.
List soil particle size of textural classes
Sand 2.0 to 0.05 mm
Silt 0.05 to 0.002 mm
Clay <0.002 mm
0.001 mm = 1 um
1 mm = 1000 um
What is soil anion and cation exchange capacity + microbes?
Microorganisms bind to negatively charged clay and OM through areas of pos charge (protiens).
Cation exchange capacity (CEC) represents the quantity of negative charge available to attract cations. Anion exchange capacity (AEC) represents the positive charge available to attract anions in solution.
What are the three states of soil water potential?
- Saturation soil pores are full of water.
- Field capacity majority of water is gone, esp large pore water
- Wilting point critical point for plants, can no longer extract water
Soil water potential - energy required to pull water from soil. The above describe water content across diff potentials.
Which soil solution components affect pH?
Water, dissolved OM, inorganic constituents, O2 and CO2.
Describe microbial activity as a function of temperature
Microbial activity increases as the optimal temperature is reached as governed by the laws of thermodynamics. The rate of chemical reactions is a direct function of temp.
What is Q10
A measure of the change in enzyme activity (reaction rate) caused by a 10C rise in temp.
Most microbial enzymes have a Q10 of 2.
Direct and indirect ways macro, meso, and microfauna interact?
Grazing - decreases microbial biomass’
Selective grazing - changes in composition
Nutrient cycling
Habitat engineering - primary production and transport of smaller fauna
Difference between detritivores and decomposers
Decomposers subsist on dead plant debris via saprotrophic feeding (fungi and bacteria perform extracellular digestion). Detritivores also subsist on dead plant debris but involves macroscopic swallowing of material.
List the 4 classes of soil organisms and an associated type
- Microflora/orgs - bacteria
- Microfauna - protozoa
- Mesofauna - mites
- Macrofauna - earthworm
Photoorganotrophs
Use light as energy source. Use organic compounds as electron donors. Many organic compounds used, depends on functional group of microbe. Eg. bacteria.
