soil biology - Stanford Universitysoils.stanford.edu/classes/GES175items/le… · PPT file · Web...
Transcript of soil biology - Stanford Universitysoils.stanford.edu/classes/GES175items/le… · PPT file · Web...
CH2O CO2
NH4+ NO3
-
Fe2+ Fe3+
H2S SO42-
NO3- NH4
+
Fe3+ Fe2+
SO42- H2S
O2 H2O
EnergyYield
Electron Donor(food)
Electron Acceptor
Edonor - Eacceptor
EnergyEnergy
CH2O
CO2
O2
H2O
NO3-CH2O
CO2 N2
Fe(OH)3CH2O
CO2 Fe2+
CH2O
CO2
SO42-
H2S
Energy YieldsDonor Acceptor
700
400
100
Eh (mV)* Condition
oxic
suboxic
anoxic
*pH 7
Aerobic Organisms
Food Source• Organic carbon*
• Ammonium Ion (NH4+)
• Ferrous Iron (Fe2+)
• Hydrogen Sulfide (H2S)
Electron Acceptor• Molecular Oxygen (O2)
CH2O CO2
NH4+ NO3
-
Fe2+ Fe3+
H2S SO42-
O2 H2O
EnergyYield
Electron Donor(food)
Electron Acceptor
Energy
-400
-36
KJ/mol
Anaerobic Organisms
Food Source• Organic carbon*
• Ammonium Ion (NH4+)
• Ferrous Iron (Fe2+)
• Hydrogen Sulfide (H2S)
Electron Acceptor• Nitrate (NO3
-)
• Manganese (Mn4+)
•Ferric Iron (Fe3+)
• Sulfate (SO42-)
CH2O CO2
NO3- NH4
+
Fe3+ Fe2+
SO42- H2S
O2 H2O
EnergyYield
Electron Donor(food)
Electron Acceptor
Energy
-400
-36
KJ/mol
- bacteria require plant for growth; plant gains ‘free’ source of available N
Nitrogen FixationNitrogen Fixation* Symbiotic relation between * Symbiotic relation between
bacteria and plants:bacteria and plants:-e.g., legumes + -e.g., legumes + RhizobiumRhizobium
* Grasses-Azospirillum/Azobactor
N-Fixation: Frankia
Frankia Nodules on Alder
- actinomycetes
- associates with desert shrubs (e.g., Ceanothus) and various tree species (e.g., alder)
Fungi-Plant Interaction
Mycorrhizae(root fungus)
- extension of root system
- fungus enhances nutrient and water intake
- plants provide carbon source
Nearly 90% of native plants have mycorrhizae association
EctomycorrhyzaeEctomycorrhyzae
- association at exterior of root- develop on evergreen trees and shrubs
MycorrhizaeMycorrhizae
- Associations occur in root interior between cells- Develop on deciduous trees, annual and herbaceous plants
Endomycorrhizae
CO2 Detritus (Plant Debris)
Fungi EarthwormsBacteria
Soil Humus
Organic Matter
Biomass
Humin(insoluble)
Humic Acid(insoluble in acid)
Fulvic Acid(soluble)
degr
adat
ion
(nonliving, nontissue decay products)
(identifiable dead tissue)
(living organisms)
Soil Humus
Organic Matter Degradation: Nutrient Cycling
Biomass
Detritus (Plant Debris)
Nutrient Release
NutrientIncorporation
-reactive functional groups: -carboxyl, hydroxyl, phenolic
Soil Organic Matter: Humus
- High cation (anion) exchange capacity
- High water holding capacity
- Promotes soil aggregation