REN R 210 FINAL

Inorganic Carbon

CO2 and carbonates in lithosphere (limestone, sodium carbonate, etc…)

Organic Carbon

SOM (C, O, H)

SOC

Active Carbon Reserve

3000 Pg

Pg= 10^15 g

Turnover = CO2, COH(SOM), CO2

Inactive Carbon Reserve

100,000,000 Pg

inorganic (carbonate), rock

Global Carbon Pools

Largest to Smallest

Carbonate(75,000,000), Oceans/Lakes (36,000) Fossil (5,000) fuels, Soil (2,400), Atmosphere (750), Vegetation(550)

Anthropogenic release of C

Tg - 10^12

420 ppm CO2

Soil Health

A soils capacity to continue to function as a vital living ecosystem that sustains plants, animals, and humans.

SOM Composition

Living Biomass: 0.5-3% - roots, microbes, animals

Residue/Detritus: 5-40%- litter, fibers, dead roots, feces (L, F layer)

Humus:

non-humic substances: 5-10% - Biopolymers, low molecular weight(known chemically)

humic substances: 40-90% - SOC stabalization

New SOM theory

accessibility to microbes, temperature for enzymes and adsorption, forms soluble in water, emphasis on carbon flow. OM is protected by minerals

Old theory

OM quality=emission prediction, stable humus, temperature sensitive, solubility in alkaline solution, emphasis on carbon stocks.

Humin – Humic Acid – Fulvic Acid

Decomposition

CHO + O2 (enzymes and microbes) = CO2, H2O,

Mineralization

Release of soluble or gaseous inorganic constituents during decomposition (e.g., nutrients, CO2).

R-NH2 (organic) —> NH4 (inorganic)

Humification

Old: - OLD theory - Condensation Rxn: low MW biopolymer to high MW biopolymer

New: NEW theory – stabilization of SOC by three mechanisms. Minerals, aggregates, decreasing molecular size.

Non-Humic substances

Known biopolymers, Easily identified chemically, Decomposition rate depends on chemical composition

Cellulose (cell wall) - 30%

Hemi-cellulose - 20%

Lignin - 20%

Lipids: 20%

Proteins: 5% (contains N)

Most to least tightly packed N

Protein, hemi-cellulose, cellulose, lignin, lipids

C/N ratio

dictates recalcification

Micro-organisms need an AVG of 8 C atoms for every 1 N atom to build biomass.

With respiration: every 24 C, microbes need to find 1 N to build biomass

C<20 = fast decomp

C>30 = slow decomp

Mean residence

time of atoms to cycle through pools

Plant residue: biopolymers, some chemical resistance

SOM “Pools”

• Chemical protection (active?)

• Physical protection (aggregates, slow)

• Organo-mineral associations (passive)

Energy source

Photo - energy from radiation

Chemo – Energy from Org. C

Litho – Energy from soil REDOX Rxn

Human and Fungi Energy source

Organic Carbon

Chemo-Heterotrophs

Nitrogen Fixation

78% of atmosphere

Organic N

C-NH2

Inorganic N

N2, NH4, NO3, N2O

Biological Fixation (lots of energy)

Rhizobium (legumes)

Frankia (alders)

N2 — nitrogenase — NH4

Nitrogenase (enzyme) must be protected from O2. Leghemoglobin scrubs O2 out of nodule.

Nitrogen Cycle

Autotrophs use CO2 to build CNH2 — microbes(heterotrophs) (ammonifiers) use SOM for e acceptor and produce NH4— nitrifiers(autotrophs) use NH4 as e acceptor and produce NO3.

Pyrogenic C (wildfire)

“passive” pool

REDOX – REDuction / OXidation Reactions

O2 +NH4 — NO3 + H2O + H2(reduction reaction)

Ammonification

Immobilized/mineralization — used by microbes to build biomass

When there is access (lower C/N ratio) — nitrification

Nitrification

NH4 + O2 = NO2 + H2O

NO2 (toxic) + O2 = NO3 + H2O

Anaerobic process

Lithoautotrophs

Denitrification

without O2, NOx is used as an e receptor

NO3— NO2 — NO — N2O— N2

Mineral Fixation

NH4 bonds to clay (very strong)

Haber Bosch Process

CH4 + N2 + O2 + H2O = NH4 + CO2 + H2O

Cuts out SOM and microbes from cycle

Eutrophication

N + P = increase in nutrients = algae = increased turbation, decreased oxygen, decreased water quality

Fresh water – 0.5-1.0 mg/L

Marine water - <0.5 mg/L

Solutions for Nutrients leaching

Plant root stimulators

Grass buffer

Capture sites (plant fireweed, aspens)

Precision ag, Regenerative ag

Acid rain

Sulfer and nitric oxide react with oxygen and water in atmosphere = Sulferic acid and nitric acid

N measurements in AOSR

IER – captures wet and dry N deposition, showed that its high on the mine sites

How is phosphorus cycle different than N cycle?

only in inorganic form (PO4 -3), no oxidation, from lithosphere

P Cycle

1.Mineral Dissolution 2.Uptake from Solution 3.Leaching/Runoff 4.Organic matter release 5.Precipitation

is insoluble when attached to Al and Fe

6.5 is best for P availability

K cycle

no redox, from lithosphere

Sulphur Cycle

redox rxn, from lithosphere

1. Mineral dissolution

2. SOM turnover

3. Atmosphere Dep

Organic forms of S

• C-S – carbon bond

• C-O-S – ester bond • Electron acceptor in anaerobic environments (WETLANDS)

Edatopic Grid

System for identifying diff ecosystems

Macrofauna

• OM shedders

• Bioturbation

• Predatory

• Ants, beetles, earthwormsetc…

Megafauna

• bioturbation

• predatory

• gophers, moles, etc…

Mesofauna

• predation

• OM consumers/shedders

• mites (0.1-1mm)

Microfauna

Nematodes, Protozoa (Ciliates, Amoebe, Flagellates)

Microflora

Fungi, Bacteria(prokaryotes), Archaea (prokaryotes)

Types of Mycorrhiza

1. Ecto (outside cell)

2. Erricoid (species specific)

3. Arbuscular (inside cell)

4. Orchid (species specific)

Microbial Size Class

Nematode, Protists, Fungi, Bacteria, Virus, Clay Particle

6 C’s of soil conservation

1. Compaction reduction 2. Conservation tillage 3. Continuous living plants 4. Cover crops 5. Crop +animal diversity 6. Composts and amendments