Chapter 6 Ecosystems

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Chapter 6 Ecosystems The Physical Environment

• Biogeochemical cycles the ways that abiotic
  matter moves throughout nature. Most important
  cycles are Carbon, Nitrogen, Phosphorus, Sulfur,
  and Water.
• The broader term nutrient cycling can also be
  used to describe the movement of these elements
  and compounds.
• To understand these, think of the various forms
  of Carbon in the Carbon Cycle (see slide 3)

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Carbon cycle Various Sinks Processes
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• Carbon is stored in various sinks (reser-voirs)
  in the Carbon Cycle moves from one sink to
  another by a variety of processes. Carbon is
  stored in the oceans as dissolved Carbon Dioxide
  gas, organic compounds, Carbonate (CO2) and
  Bi-carbonate ions (HCO2-). Certain algae remove
  Calcium ions (Ca) and Carbonate ions to form
  Calcite (CaCO3) for their internal structures.
  Dissolved CO2 is removed by aquatic plants,
  cyanobacteria, etc., for photosynthetic
  production of biomass sugars for stored energy.

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• On land, carbon sinks include exposures of
  limestone, living biomass (trees, plants,
  animals), and soil humus. Below the surface, it
  is stored in various forms of coal, organics in
  sediments that become petroleum (over time), and
  natural gas.
• Carbon is released to the atmosphere as Carbon
  soot, Carbon Dioxide and Carbon Monoxide by
  combustion, animal/bacteria respiration, volcanic
  exhalations, hot spring emissions, release from
  oceans,

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• Nitrogen Cycle is important because of its role
  as a component of proteins and nucleic acids.
  Atmospheric nitrogen (N ) is stable and is not
  available for use in organic processes, it must
  undergo nitrogen fixing processes (pp. 106-107),
  w/in the soil, these processes are driven by
  bacteria. Active forms of Nitrogen include
  ammonium ion (NH4), nitrate ion (NO3-), and
  nitrite ion (NO2-).
• Nitrogen concerns groundwater pollution by
  nitrates nitrites, nitrogen oxides from auto
  exhaust contribute to photochemical smog during
  summer heat.

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• Phosphorous Cycle is important as phos-phorous
  is an important trace element for many organisms.
  Phosphorous does not form gases, rather it
  cycles as various compounds through the soil and
  tissues of plants and animals.
• Problems include removal of phosphorous by crop
  growth for cattle human use, phosphorous in
  waste material ends up in water and then into the
  oceans, where it is lost to human use, rather
  than being cycled back into the land as humus.

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• Sulfur is a vital component of proteins the
  Sulfur Cycle is largely driven by bacteria (p.
  110). Sulfur compounds are very reactive, thus
  they are very mobile. Sulfur gases released to
  the atmosphere include Hydrogen Sulfide (H2S),
  Sulfur Dioxide (SO2), Sulfur Trioxide (SO3).
  When mixed with rainfall, these produce sulfur
  acids. Most intense gas concentrations are
  associated with volcanoes, oil wells
  refineries, mineral smelters.
• Sulfur is deposited in anoxic conditions in
  aquatic conditions of poor circulation.

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• The Hydrologic Cycle is the dynamic move-ment
  of water through the atmosphere, over below the
  land surface, through the life cycles of plants
  and animals, and to and from the oceans other
  water bodies.
• Components include Conversion of water to water
  vapor (Evaporation) Evaporation through plant
  leaves (Transpiration) Conversion of water vapor
  to water drop-lets (Condensation) Oversaturation
  of water vapor in clouds rainfall/snowfall
  (Precipitation) Precipitation leads to run-off
  to surface waters infiltration to ground water.

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• Hydrologic Cycle is largely driven by Solar
  Energy, Heat Exchange, and Gravity.

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• Solar Energy 1 billionth of Suns energy
  reaches the Earth. 31 is immediately reflected
  back into space by clouds and surfaces.
  Remainder is absorbed and runs hydrologic cycle,
  drives winds ocean surface currents, drives
  photosynthesis, warms the planet.
• Albedo is the proportional reflectance of
  different aspects of Earths surface.
  Glaciers/Ice Sheets 80 90. Asphalt 10
  15 reflectance. Forests 5.
• Eventually, all of the absorbed sunlight returns
  to space as longwave infrared (heat or thermal)
  energy.

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• Variations in Earth surface temperatures
  climate are due to Inclination of Earths axis
  in relation to the Sun and the Unequal
  Distribution of Land vs. Water Differen-tial
  Thermal Characteristics of Land Water.
  Long-term changes may be due to variations in
  Solar activity Earth orbit.
• Lower angle of Suns rays hitting Earth more
  surface area coverage/less concentration.
• Seasonal changes are largely due to Earths axial
  inclination in relation to the Sun.

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Axial inclination responsible for Seasonal
Variations.
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• Atmosphere Dry atmosphere composed of 78
  Nitrogen (N2) 21 Oxygen (O ). Remaining 1
  composed of Argon, Carbon Dioxide, Neon, Helium,
  and other trace gases.
• Important atmospheric functions include shielding
  Earths surface from UV, X-rays, cosmic rays from
  space, while allowing visible and infrared
  wavelengths to penetrate atmosphere. Greenhouse
  Effect shields Earth from excessive diurnal
  temperature variations (day to night temperature
  variations).

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• Atmospheric Layers Most important are
  Troposphere (surface to 11 miles) Stratosphere
  (11 to 16 miles). Other layers listed on p. 115.
• Troposphere Weather maker, turbulent, rich in
  water vapor/droplets.
• Stratosphere Ozone shield, steady wind, but
  little turbulence. Ozone not present as a
  layer, but is more prevalent from 11 to 16
  miles above Earths surface. Oxygen (O2) and
  Ozone (O3) both block UV radia-tion, but Ozone is
  more dense, more effi-cient, but is also
  unstable. Thinning seems seasonal, greatest in
  September.

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• Atmospheric Circulation caused by
• Earths Rotation
• Uneven Distribution of Land Mass
• Properties of Heat Transfer between
  air/water/land
• Solar Energy
• Horizontal/Latitudinal Wind Belts Rossby
  Regime.
• 00 to 300 North Northeast Trade Winds
• 300 to 600 North Westerlies Wind Belt Jet
  Stream
• 600 to 900 North Polar Easterlies

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Vertical atmospheric circulation Hadley
cells Driven by Equatorial Heating (Equatorial
Low Pressure Zone).
Low Pressure Zones Rising Air. High Pressure
Zones Falling Air. Strongest cells _at_ Equator
(above land) at Poles due to Convergence (Polar
High).
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The combined actions of the Horizontal Wind
Belts, the Hadley Cells, the Earths rotation
lead to the Coriolis Effect, i.e., clockwise
rotation of ocean currents in Northern
Hemisphere. Example Gulf Stream carries heat
from sub-tropics northward, warms Scandinavia,
British Isles. The North Pacific Drift carries
enough heat to warm the NW coastline of North
America. The wind-driven surface circulation
patterns, called gyres, are influenced by
landmass locations and coastline shapes.
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Major Surface Ocean Currents (Fig. 6.13)
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• The varying density of sea water largely
  affects vertical ocean currents. Colder, saltier
  water tends to sink, while warmer, less salty
  water remains near the oceans surface.

Present-day circulation
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• There is evidence of past changes in the ocean
  conveyor belt, but all of the reasons are not
  known. Weakening of the North Atlantic Gulf
  Stream component may bring about another ice age.
• El Niño Southern Oscillation periodic changes
  in wind/oceanic current patterns in Pacific
  Ocean. May be driven by solar activity. Under
  normal conditions NE Trade Winds SE Trade
  Winds combine to form E to W moving winds along
  Inter-Tropical Convergence Zone across Pacific
  Ocean. Every 3 to 7 years, these winds weaken.

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Under normal conditions Convergence of Trade
Winds push surface water to the west, causing an
upwhelling of cold, organic-rich bottom water
along the West Coast of South America.
Under El Niño conditions weakening of trade
winds weakening of upwhelling, affecting E.
Pacific eco-systems weather.
South America
Pacific Ocean
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Global weather changes due to El Niño, may
cause temperature spikes, e.g., 1998 El Niño.
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ENSO - Solar Activity Model
La Niña stronger trade winds
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• Weather Climate
• Weather short-term atmospheric conditions.
• Climate 30 year averages of atmospheric
  conditions. Temperature Moisture most
  important factors. Climate influences include
  Latitude, Elevation, Topography, Vegetation,
  Distance from Ocean, Position on Continent.
• Climate zones defined by Köppen (Fig. 6.18) Six
  climate zones, subdivided into climate types (p.
  121).

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Temperatures largely determined by Latitude
closer to Equator more direct sunlight. Also,
altitude, cloud cover affect temps. Moisture is
affected largely by Distance from Ocean and the
Position on the Continent. Mechanisms for
Atmospheric Uplift needed for Condensation of
Water Vapor rain/snow Low Pressure Weather
Systems Cyclonic Counter clockwise rotation,
uplift of air Convection Uplift by heat
Orographic Effect Uplift by mountains (slide
25)
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• Orographic Effect - Uplift of Air Masses by
  Mountains.

Pacific Ocean
Coastal Ranges, Sierra Nevada, Cascades, Rocky
Mts.
NW Washington, Olympic Peninsula 180 to 200 in.
of rain/year, eastern WA 20 in./yr.