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Biogeochemical Cycles - 1. Class Lecture Goals 1. What are systems? 2. What are biogeochemical cycles? 3. Why are they important? 4. What is common about them? 5. Carbon and nitrogen cycles 6. Focus on the Water Cycle (Monday). Today’s Topic: “Did Logging Worsen Floods?”.

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biogeochemical cycles 1

Biogeochemical Cycles - 1

Class Lecture Goals

1. What are systems?

2. What are biogeochemical cycles?

3. Why are they important?

4. What is common about them?

5. Carbon and nitrogen cycles

6. Focus on the Water Cycle (Monday)

today s topic did logging worsen floods
Today’s Topic: “Did Logging Worsen Floods?”
  • State Senate Committee
  • Weyerhaeuser Co.
  • State DNR
  • David Montgomery
  • Phil Mote
  • Ideas
    • System: Watershed
    • Cumulative effects
    • Climate Change
what is a system


What is a system?
  • System: a collection of matter, parts, or components which are included inside a specified, often arbitrary, boundary. Example: Ecosystem
  • Systems often have inputs and outputs.
  • For dynamic systems, by definition, one or more aspects of the system change with time.
    • Example of a simple dynamic system: bathtub or your ‘bank’ account.


  • The boundary of a dynamic system is chosen for convenient conceptual separation for the system

Carbon dioxide




reading assignments
Reading Assignments

• Examine this web page


select the true statement from below for the pnw climate change will


Answer Now!

Select the true statement from below for the PNW: Climate change will
  • Increase precipitation & snowpack
  • Increase temperature & snowpack
  • Increase precipitation & decrease snowpack
what are biogeochemical cycles
What are biogeochemical cycles?
  • Earth system has four parts
    • Atmosphere
    • Hydrosphere
    • Lithosphere
    • Biosphere
  • Biogeochemical cycles: The chemical interactions (cycles) that exist between the atmosphere, hydrosphere, lithosphere, and biosphere.
  • Abiotic (physio-chemical) and biotic processes drive these cycles
  • Focus on carbon and water cycles (but could include all necessary elements for life). N - cycle weakly touched on!
what is common amongst them
What is common amongst them?
  • Each compound (water, carbon, nitrogen) typically exists in all four parts of the Earth System
  • There are
    • ‘Pools’
    • Fluxes in and out of pools
    • Chemical or biochemical transformations
  • Transformations
    • are important
    • can lead to positive & negative consequences

Examples of Transformations

Carbon cycle: Organic compounds to CO2 (processes: respiration, decomposition, or fire)

Carbon cycle: CO2 to organic compounds (process: photosynthesis)

Nitrogen cycle: N2 to NO3 (atmospheric nitrogen to plant utilizable nitrate) (process: N-fixation)

Nitrogen cycle: N2 to NH3 (plant utilizable ammonia) (process: Haber-Bosch Industrial N-fixation)

Water cycle: Liquid water to water vapor (process: evaporation and evapo-transpiration)

Water cycle: Water vapor to liquid water (process: condensation)


Carbon Cycle


carbon cycle data



Carbon Cycle Data
  • Burning of fossil fuels
  • Land conversion
  • Cement
  • Role of Oceans
  • Role of terrestrial plants (trees & soils)


changes in atmospheric c0 2 2

Changes in Atmospheric C02 - 2
key aspects of the carbon cycle
Key Aspects of the Carbon Cycle
  • Carbon is the skeleton of all life.
  • Carbon dioxide is a critical gas:
    • Taken up by plants in photosynthesis
    • Released by plants and animals in respiration
    • Released during decomposition (and fires)
    • Greenhouse gas (greenhouse effect - your car in the sun)
nitrogen cycle

Forms of Nitrogen (N2)

N2 - inert gas, 78% of the atmosphere

NO, N20, NO2 - other gases of nitrogen, not directly biologically important. Part of the gases found in smog.

NO3- (nitrate) and NH4+ (ammonium) -- ionic forms of nitrogen that are biologically usable.

Nitrogen Cycle

nitrogen cycle1

Forms & Sources of biologically available nitrogen (N2)

  • For plants
  • NO3- (nitrate)
  • NH4+ (ammonium)
  • Sources: N-fixation by plants (N2 to NH3 and N2 to NO3), lightening, bacteria decomposition of organic N (amino acids & proteins)
  • For animals
  • Organic forms: amino acids and proteins (from plants or other animals)
Nitrogen Cycle

nitrogen cycle2

Losses of nitrogen from system

  • In bogs, lakes (places of low oxygen), NO3- is converted to N2 by bacteria (get their oxygen from the NO3)
  • Volatilization of NH4+ (urea) to ammonia gas (NH3) - warm, dry conditions.
  • Leaching of NO3- (nitrate)
  • Erosion
  • Fire (combustion)
Nitrogen Cycle

nitrogen cycle key points
Nitrogen Cycle: Key Points
  • Nitrogen is in the atmosphere as N2 (78%)
  • N2 is an inert gas and cannot be used by plants or animals
  • N2 can be converted to a usable form via
    • Lightening
    • N-fixing plants and cyanobacteria
    • Industrial process (energy intensive)
  • Nitrogen limits plant growth
  • Nitrogen is easily lost from biological systems
  • 1. What are systems?
  • 2. What are biogeochemical cycles?
  • 3. Why are they important?
  • 4. What is common about them?
  • 5. Carbon and nitrogen cycles