Chapter 4Chapter 4Biogeochemical CyclesBiogeochemical Cycles

Lake Washington Case StudyLake Washington Case Study

What is a biogeochemical cycle?What is a biogeochemical cycle?

Path a chem takes through air, water, soil, Path a chem takes through air, water, soil, orgs. and back to air or soilorgs. and back to air or soil

Time taken to cycle varies.Time taken to cycle varies. Gaseous elements faster Gaseous elements faster Non-gaseous slowerNon-gaseous slower

Geologic CyclesGeologic Cycles

Tectonic CycleTectonic Cycle

Top layer (Top layer (lithospherelithosphere) is constantly created ) is constantly created and destroyed. Large segments (tectonic and destroyed. Large segments (tectonic plates) move past one another.plates) move past one another.

Transform fault = Transform fault =

Convergent =Convergent =

Divergent =Divergent =

Transform fault = sliding Transform fault = sliding

Convergent = collidingConvergent = colliding

Divergent = spreadingDivergent = spreading

Hydrologic Cycle: Ch 19 in detailHydrologic Cycle: Ch 19 in detail

Major Global CyclesMajor Global Cycles

CarbonCarbon NitrogenNitrogen PhosphorusPhosphorus

Where do we find C?Where do we find C? Does it have an atm stage?Does it have an atm stage? How might carbon cycle be thrown out of How might carbon cycle be thrown out of

balance?balance?

What happens if out of balance?What happens if out of balance?

The Carbon CycleThe Carbon Cycle Gaseous (COGaseous (CO2 2 , CH, CH44). Most important organic compound.). Most important organic compound.

Nitrogen CycleNitrogen Cycle

Where do we find N?Where do we find N? Does it have an atm stage?Does it have an atm stage? How might the nitrogen cycle be thrown out of How might the nitrogen cycle be thrown out of

balance?balance? What happens if out of balance?What happens if out of balance?

Nitrogen CycleNitrogen Cycle NN2 2 = most of the atm = most of the atm

(about 80%)(about 80%)

110 m. tons annually110 m. tons annually

10 m. tons annually10 m. tons annually

Nitrogen cycle key steps!!:Nitrogen cycle key steps!!: First in atmosphere as NFirst in atmosphere as N22

Then in the soil: Then in the soil: 1. 1. Nitrogen fixation:Nitrogen fixation: fixes N fixes N22 to a form to a form

plants can use plants can use 2. Other bacteria convert ammonia into 2. Other bacteria convert ammonia into

nitratesnitrates ( NO ( NO33 ) )

Into living things:Into living things: 3. Plants absorb nitrates and ammonia by3. Plants absorb nitrates and ammonia by

assimilationassimilation

Back into soil again:Back into soil again:

Back into the atm againBack into the atm again

80% N2 in atm

Ammonification

Nitrification step1

Nitrification step2

Assimilation

Nitrogen fixation

Denitrification

Symbiosis - Crop RotationSymbiosis - Crop Rotation

PhosphorusPhosphorus

Phosphorus has no atm stage.Phosphorus has no atm stage. How does this affect its’ use by l.t.s?How does this affect its’ use by l.t.s?

Phosphorus CyclePhosphorus Cycle

No gaseous phaseNo gaseous phase

Stored in rocks and organic material in soilStored in rocks and organic material in soil Thanks to microbial action, changed to phosphates Thanks to microbial action, changed to phosphates

(PO(PO4 4 3-3-

or HPO or HPO4 4 2- 2- )which plants can access. (slowly))which plants can access. (slowly)