Nutrient cycles and soils

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• Nutrient cycles and soils

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Nutrient Cycling in Ecosystems

• Continuous flow of important atoms, ions,
  molecules between living organisms and nonliving
  environment

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Hydrologic Cycle (water)

• Hydrosphere-main storage, but water cycles
  continuously locally, regionally, globally
• Crucial for life
• availability of water determines what organisms
  can survive in specific location

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Water cycle

• Collects, purifies and distributes H2O
• Evaporation-conversion of water into vapor
• Transpiration-water evaporating from plants after
  being drawn through the plant

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• Condensation-converts water vapor to liquid
• Precipitation-rain, snow, sleet, hail
• Infiltration-water moves into soil
• Percolation-downward flow through soil to
  aquifers
• runoff-surface movement to oceans/above ground
  reservoirs

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Water Unique Properties

• Hydrogen bonds-reason behind the uniqueness
• High boiling point, low freezing point
• Can store great amounts of heat
• Much heat needed to evaporate

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Few more.
Cool stuff eh?

• Can dissolve wide variety of compounds
• High surface tension, high wetting ability
• (allows water to move through capillary action)
• Water expands when freezing-floats
• (water freezes from top down)

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• Absolute humidity-amt of water in certain mass of
  air (g/kg)
• Relative humidity-amt of water vapor in certain
  mass of air, relative to current temperature

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Human Influence on Water

• Withdraw massive amounts from aquifers, streams,
  lakes
• groundwater depletion, salt water intrusion
• Clearing vegetation from land
• increased runoff, flooding, erosion, landslides
• Add nutrients and pollutants-degrades quality

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5-3 The Carbon Cycle

• Building block of all organic compounds necessary
  to life
• Chemical energy stored as bonds between carbon
  and other atoms
• movement of C in food webs flow of energy
• CO2 major greenhouse gas

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• Gaseous cycle-carbon dioxide makes up .036
  atmospheric gas is dissolved in water
• Producers use CO2 gas in photosynthesis and
  convert to glucose
• cycles rapidly

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• Consumers and decomposers break down glucose in
  aerobic respiration, C reenters atmosphere as CO2
• Reused by producers
• Oxygen and hydrogen cycle with carbon

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Carbon storage

• Wetlands-highly productive, deposits of plant
  material bacteria accumulate faster than can be
  decomposed
• buried organic matter compressed between layers
  of sediment
• millions of yearsfossil fuels

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• Limestone (CaCO3) sedimentary rock-largest
  storage reservoir of carbon
• Released very slowly as sediments dissolve
• Ocean-2nd largest storage-CO2 is soluble
• warm water releases more (soda.)

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Humans influencing carbon cycle

• Deforestation, vegetation removal has left less
  vegetation to absorb CO2 gas w/ photosynthesis
• Fossil fuels wood burned releases more CO2 into
  air than producers can use
• pollution
• global warming

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5-4 Nitrogen Cycle

• Necessary for amino acid, protein, DNA, RNA
  production
• Nitrogen is in limited supply at any given time
  and is a limiting factor to primary productivity

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• Atmosphere in the troposphere-78 N2 gas
• Producers consumers cannot absorb or use it as
  a gas
• Nitrogen fixing bacteria, lightening-only things
  that can convert nitrogen gas into usable
  form-ammonia
• N2 3H2 ? 2NH3

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• Cyanobacteria-in soil and water
• Rhizobium bacteria-in legumes (soybean, clover)
• Plants can use ammonia w/water
• Nitrification-bacteria convert ammonia in soil to
  nitrite ions (toxic) then to nitrate ions
  (nutrient)

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• Ammonification-Decomposers turn nitrogen rich
  waste dead organisms back into ammonia and
  ammonium salts
• Denitrification-other specialized bacteria
  convert nitrogen back into nitrites and nitrates
  and back into nitrogen gas
• Problem-ions are easily soluble can be removed by
  water

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Human influence on nitrogen cycle

• Originally nitrogen fixation by microorganisms
  only source
• WWII Fritz Haber-used high temperatures and high
  pressure to create gaseous ammonia
• used as fertilizer

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• Burning fuels -releases nitrogen oxides-nitrogen
  and oxygen
• combine at high temperatures
• NOx is air pollution, turns into acid when reacts
  w/ water-contributes to acid rain
• Smog formation
• Greenhouse gas, global warming, depletes ozone

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• Remove nitrogen from crust when mine for
  fertilizer components
• deplete nitrogen from soil by harvesting N rich
  crops
• leach out nitrate ions w/ poor irrigation
• Remove nitrogen w/ burning and clearing native
  plants while emitting NOx

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• Excess nitrogen enters water system-agricultural
  runoff, sewage discharge-algae loves, depleting
  water oxygen
• Add nitrogen to system with acid deposition

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5-5 Phosphorus cycle

• Part of DNA, in cell membranes, nucleic acids
• Moves slowly from sedimentary deposits on land
  shallow ocean deposits to living organisms and
  back to land

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• Human scale-phosphorus is one way
• found as phosphate salts-released by weathering
  (slow breakdown) of rock
• plants take up released phosphates through roots
• animals eat producers, decomposers return
  phosphate to soil water

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Human influence on phosphorus cycle

• Mine phosphorus for fertilizer, depletes crust
• Cutting tropical forests-all phosphorus in living
  organisms w/ rapid cycling, nothing can grow in
  soil w/o native organisms
• excess phosphate added to aquatic ecosystems,
  algae loves, depletes oxygen

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5-6 Sulfur cycle

• Component of proteins and vitamins
• Sulfur tied up in rocks (minerals) and much is
  buried
• Hydrogen sulfide-gas, poisonous from volcanoes
  and anaerobic decomposers
• sulfate salt spray from ocean

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• Sulfur dioxide (SO2) reacts with oxygen sulfur
  trioxide gas
• reacts w/water becomes acidic
• major component of ACID RAIN

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Human influence on sulfur cycle

• 1/3 of all sulfur in atmosphere comes from human
  activity (99 of sulfur dioxide)
• high sulfur coal oil-low quality very
  polluting
• refining petroleum
• smelting metals to release sulfur
• much industry