Lecture 16 Flashcards
How many carbon atoms do microorganisms need to build biomass
8C : 1N
24 C microbes needed to find 1 N to build biomass
Define decomposition
Chemical Rxn occurring during decay of plant/animal remains
Altered chemical composition produces energy
Define Mineralization
Release of soluble or gaseous inorganic constituents during decomposition
What does SOC release during mineralization
CO2
What does SON release during mineralization
NH4
Define Humification
Decomposition results in black, greasy OM
What was the old theory of Humification
Condensation Rxn: low MW biopolymer becomes high MW biopolymer
What is the new theory of Humification
Stabilization of SOC by three mechanisms
What are 5 Non-humid substances
- Cellulose
- Hemi-cellulose
- Lignin
- Lipids
- Protein
What is cellulose
Linear polymer of glucose units
~30% of plant material
What is Hemi-cellulose
Branched polymer of different sugars
~20% plant material
What is lignin
Branched, aromatic polymer
~20% of woody plant material
What are Lipids
Fats, waxes
~20% cellular material
What is protein
-amino acids (N is present)
-Biochemical “machine”
-5% plant material
Decomposition gradient of non humid substances (easiest to hardest to decompose)
Protein > Hemicellulose > Cellulose > Lignin > Fats
What is the historic method for examining soil fertility
Humic fractions
What do microbes use to cleave off functional groups
Enzymes
What are the 3 limits for decomposition
- Size of molecule
- Aggregate
- Mineral associated organic matter
What is the soil carbon model
Plant Animal Residue > Soil > Microbe Enzymes > Energy Biomass > SOM stability
What is mean residence time
-time of atoms to cycle through pools
-plant residue: biopolymers, some chemical resistance
What are the 3 SOM Theoretical Pools
-Chemical Protection
-Physical Protection (aggregation)
-Organo-mineral associations
What carbon source do Autotrophs use
CO2
What carbon source do Heterotrophs use
Org.C
What Energy Source do photoautrophs use
Suns energy
What energy source do chemoautotrophs use
Energy from organic C
What energy do lithoautrophs use
Energy from soil REDOX Rxn
