MATTER CYCLING IN ECOSYSTEMS

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Mechanicalenergy(moving,thinking,living)
Chemical energy (photosynthesis)
Chemical energy (food)
Solar energy
Waste Heat
Waste Heat
Waste Heat
Waste Heat
Fig. 2-14, p. 45
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SUSTAINABILITY AND MATTER AND ENERGY LAWS

• Unsustainable High-Throughput Economies Working
  in Straight Lines
• Converts resources to goods in a manner that
  promotes waste and pollution.

Figure 2-15
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Sustainable Low-Throughput Economies Learning
from Nature

• Matter-Recycling-and-Reuse Economies Working in
  Circles
• Mimics nature by recycling and reusing, thus
  reducing pollutants and waste.
• It is not sustainable for growing populations.

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Inputs (from environment)
System Throughputs
Outputs (into environment)
Energy conservation
Low-quality Energy (heat)
Energy
Sustainable low-waste economy
Waste and pollution
Waste and pollution
Pollution control
Matter
Recycle and reuse
Matter Feedback
Energy Feedback
Fig. 2-16, p. 47
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Biogeochemical Cycling

• The cycling of nutrients through ecosystems via
  food chains and food webs, including the exchange
  of nutrients between the biosphere and the
  hydrosphere, atmosphere and geosphere (e.g.,
  soils and sediments)

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MATTER CYCLING IN ECOSYSTEMS

• Nutrient Cycles Global Recycling
• Global Cycles recycle nutrients through the
  earths air, land, water, and living organisms.
• Nutrients are the elements and compounds that
  organisms need to live, grow, and reproduce.
• Biogeochemical cycles move these substances
  through air, water, soil, rock and living
  organisms.

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Transfer v Transformation

• Transfers flow through a system and involve a
  change in location
• Transformations lead to interaction within a
  system in the formation of a new end product or
  involving a change of state.
• As we discuss various cycles, underline
  transfers, and circle transformations.

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Flows v Storage

• Sometimes matter flows through a cycle and
  sometimes it is stored.
• When a material is flowing through a cycle
  (conversion), color it green.
• When it is being stored (sink), color it red.

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Nutrient cycles and energy flow
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The Water Cycle
Figure 3-26
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Waters Unique Properties

• There are strong forces of attraction between
  molecules of water.
• Water exists as a liquid over a wide temperature
  range.
• Liquid water changes temperature slowly.
• It takes a large amount of energy for water to
  evaporate.
• Liquid water can dissolve a variety of compounds.
• Water expands when it freezes.

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Effects of Human Activities on Water Cycle

• We alter the water cycle by
• Withdrawing large amounts of freshwater.
• Clearing vegetation and eroding soils.
• Polluting surface and underground water.
• Contributing to climate change.

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The global carbon cycle
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The Carbon CyclePart of Natures Thermostat
Figure 3-27
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Carbon

• Photosynthesis and Respiration provide a link
  between the atmosphere and terrestrial
• environments.
• Decomposition recycles carbon to the soil and
  back to atmosphere
• Fires oxidize organic material to CO2 (burning)
• Organic detritus, under intense pressure,
  changes into coal and petroleum in rock.
• Limestone keeps carbon out of circulation
• Weathering of exposed limestone releases carbon
• A carbon atom cycles about every six years

• The basic constituent of all organic compounds

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Human impacts on the carbon cycle

• Human intrusion into the cycle is significant
• We are diverting or removing 40 of the
  photosynthetic effect of land plants
• Burning fossil fuels has increased atmospheric
  CO2 by 35
• Deforestation and soil degradation release
  significant amounts of CO2 to the atmosphere
• Recent reforestation and changed agricultural
  practices have improved this somewhat

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The Nitrogen Cycle Bacteria in Action
Figure 3-29
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The global nitrogen cycle
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Major Components of Nitrogen Cycle
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The nitrogen cycle

• Is a unique cycle
• Bacteria in soils, water, and sediments perform
  many steps of the cycle
• Nitrogen is in high demand by aquatic and
  terrestrial plants
• Air is the main reservoir of nitrogen (N)
• Nonreactive nitrogen most organisms can not use
  it
• Reactive nitrogen (Nr) other forms of nitrogen
  that can be used by organisms

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Plants take up nitrogen

• Plants in terrestrial ecosystems (non-N-fixing
  producers)
• Take up Nr as ammonium (NO4) and incorporate it
  into proteins and nucleic acid compounds
• The nitrogen moves through the food chain to
  decomposers, releasing nitrogen wastes
• Soil bacteria (nitrifying bacteria) convert
  ammonium to nitrate to obtain energy
• Nitrate is available for plant uptake
• Nitrogen fixation bacteria and cyanobacteria can
  use nonreactive N and convert it to a usable form

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The Nitrogen Cycle

• Nitrogen Fixation
• Bacteria convert gaseous nitrogen to ammonia
• (N2) (NH3)
• Some ammonia enters the ground normally through
  waste and decay as well (pee, poop and dead
  things).

Different bacteria convert ammonia to
nitrite (NH3) (NO2-)
Bacteria use nitrite as an energy source, and
give off nitrate (NO3-) as waste Nitrate is
then taken up by plants or released into the
atmosphere, where it becomes gaseous N2 again.
(NO3-)
(N2)
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Nitrogen fixation
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Effects of Human Activities on the Nitrogen Cycle

• We alter the nitrogen cycle by
• Adding gases that contribute to acid rain.
• Adding nitrous oxide to the atmosphere through
  farming practices which can warm the atmosphere
  and deplete ozone.
• Contaminating ground water
• from nitrate ions in inorganic
• fertilizers.
• Releasing nitrogen into the
• troposphere through
• deforestation.

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The global phosphorus cycle
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The Phosphorous Cycle
Figure 3-31
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The phosphorus cycle

• Mineral elements originate in rock and soil
  minerals
• A shortage of phosphorus is a limiting factor
• Excessive phosphorus can stimulate algal growth
• As rock breaks down, phosphate is released
• Replenishes phosphate lost through leaching or
  runoff
• Organic phosphate incorporated into organic
  compounds by plants from soil or water

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Human impacts on the phosphorus cycle

• The most serious intrusion comes from fertilizers
• Phosphorus is mined and made into fertilizers,
  animal feeds, detergents, etc.
• When added to soil, it can stimulate production
• Human applications have tripled the amount
  reaching the oceans, accelerating the cycle
• It cant be returned to the soil
• Excess phosphorus in water leads to severe
  pollution
• Can cause too many bacteria and fish kills

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The Sulfur Cycle
Figure 3-32
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Why sulfur?

• -In nature, it can be found as the pure element
  and as sulfide and sulfate minerals.
• -It is an essential element for life and is found
  in two amino acids cysteine and methionine.
• -Its commercial uses are primarily in
  fertilizers, but it is also widely used in black
  gunpowder, matches, insecticides and fungicides.

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Effects of Human Activities on the Sulfur Cycle

• We add sulfur dioxide to the atmosphere by
• Burning coal and oil
• Refining sulfur containing petroleum.
• Convert sulfur-containing metallic ores into free
  metals such as copper, lead, and zinc releasing
  sulfur dioxide into the environment.

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Serious consequences of fertilization

• Nitric acid has destroyed lakes, ponds, and
  forests
• Atmospheric nitrogen oxides adds to ozone
  pollution, climate change, and stratospheric
  ozone depletion
• Abundant nitrates are not incorporated into
  organisms
• They are released into the soil, where they leach
  calcium and magnesium
• Eutrophication of waterways
• Nitrogen cascade complex of ecological effects
  as Nr moves through the environment

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Comparing the cycles

• Carbon is mainly found in the atmosphere
• Directly taken in by plants
• Nitrogen and phosphorus are limiting factors
• All three cycles have been sped up by human
  actions
• Acid rain, greenhouse gases, eutrophication
• Other cycles exist for other elements (e.g.,
  water)
• All go on simultaneously
• All come together in tissues of living things