Nutrient Cycling

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Nutrient Cycling

• BIO 325 Chapter 19

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Generalizations

• Matter moves around the earth in cycles
• Energy, as we understand it, moves in a straight
  shot i.e. it is not cycled
• We will look at decomposition
• We will look at the following cycles
• Phosphorus
• Nitrogen
• Carbon (already looked at with global warming)
• Affects of disturbance on cycles

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Phosphorus

• Why is it important to organisms?

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Phosphorus Cycle

• Global phosphorus cycle does not include
  substantial atmospheric pool.
• Largest quantities found in mineral deposits and
  marine sediments.
• Much of this in forms not directly available to
  plants.
• Slowly released in terrestrial and aquatic
  ecosystems via weathering of rocks.

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Phosphorus cycle
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Phosphate in Florida

• Marine deposits
• Made into phosphate fertilizer
• Most U.S. phosphate fertilizer comes from Florida
• Hardee, Polk counties

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Why is Nitrogen important to organisms?
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Nitrogen Cycle

• Includes major atmospheric pool - N2.
• Only nitrogen fixers can use atmospheric supply
  directly.
• Energy-demanding process.
• N2 reduced to ammonia (NH3).
• Once N is fixed it is available to organisms.
• Upon death of an organism, N can be released by
  fungi and bacteria during decomposition.

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Nitrogen cycle
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Nitrogen Fixation
Root Nodules

• Atmospheric nitrogen converted to ammonia
• N2 ? NH4 or NH3
• Conducted either by soil bacteria
• Or by bacteria in roots (e.g. Rhizobium)
• Example Alder

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Nitrogen Fixation found in legumes
Root Nodules
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Denitrification is opposite of fixation

• Denitrification
• or NO2 or NO3 ? N2
• Also occurs by bacteria
• Nitrogen goes into atmosphere

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Carbon cycle

• Moves between organisms and atmosphere as a
  consequence of photosynthesis and respiration.
• In aquatic ecosystems, CO2 must first dissolve
  into water before being used by primary
  producers.
• Although some C cycles rapidly, some remains
  sequestered in unavailable forms for long periods
  of time.

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Carbon Cycle
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Decomposition

• It happens
• You will experience it
• Hopefully, after you die

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Changes in Carbon Cycle results in

• Global climate change changes
• Local/regional disturbance (e.g. storms, floods,
  fires) regime changes
• Vegetation (forests)
• Example change of forest fires in the Western
  U.S.
• 60 minutes video

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Decomposition varies with

• Temperature, moisture and chemical composition

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Lignin vs. nitrogen content in leaves

• Lignin makes leaves tough
• Resist fungal decomposition

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Memorize this molecule!!
Our Dear Friend, Lignin
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Nitrogen cycling changes by invasive species

• N-fixing tree Myrica faya is altering N dynamics
  of Hawaiian ecosystems.
• Introduced in late 1800s as ornamental or
  medicinal plant, and later used for watershed
  reclamation.
• Nitrogen fixation by Myrica large N input.

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Dont forget

• 1st test next Friday ,November 2nd (changed from
  Wednesday ,Oct. 31st)
• Powerpoints and study guide will be posted on
  website faculty.saintleo.edu/miller
• 2nd reading due on November 5th

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Ecosystem is Completely Altered with M. faya

• M. faya high N inputs allow other species to
  invade
• Also this N-fixing ability allows for M. faya to
  overtop native trees and shade them out
• High N content of leaves changes soil