For each energy transfer in a food chain

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• For each energy transfer in a food chain
• About 90 used for consumer maintenance
• ca. 10 is converted into biomass
• potential food (energy) for other organisms
• Average energy transfer efficiency
• ca. 10 (5-20)

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Measuring primary production

• Terrestrial plants
• 1. Changes in CO2 or O2 concentration in air
  around plant.
• CO2 uptake in daylight measure net production
  because both photosynthesis and respiration are
  occurring.
• CO2 release at night estimates respiration.
• Expensive instrumentation. Seldom used routinely
  in field.
• Aquatic production easier O2 differences (light
  bottle dark bottle).
• 2. Harvest method (simplest). Plant biomass
  produce
• ?B B2 B1
• NPP ?B L G

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• A known weight of oven dried plant or animal
  matter is burned in a bomb calorimeter.
• Amount of heat given off is determined
• The energy content (heat yield) is approximately
• 4 to 4.5 kcals/gram plant matter
• 5 to 5.5 kcals/gram animal matter
• Has to be done for each species, each plant part,
  each season

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Factors limiting primary production Fresh-water
lakes 1. Depth of light penetration
2. Temperature 3. Nutrients P, N
Clear Lake Castle Lake Lake Tahoe California
eutrophic Shift from clear-water, algae To turbid
green water, cyanobacteria Nutrient runoffs from
cities and agriculture
oligotrophic
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Phosphorus limitation of primary production in
170 freshwater lakes
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Large scale, experiments Experimental Lakes NW
Ontario A P, N (phytoplankton population
response) B N (no change)
A
B
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Primary production in oceans light not a
limiting factor N, Fe, Si
Depth In m
Phytoplankton
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Primary production in oceans
Duck farms
H2O samples
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Terrestrial primary production

• Related positively to temperature and
  precipitation
• which determine length of growing season.
• Visualized by relationship between net primary
  production and evapotranspiration.

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Energy stored as carbon compounds in plant
tissues. Amount of C fixed is controlled by 1.
Climate 2. Leaf area per unit of ground area Up
to 12 (layers) in some forests. Number of layers
determined by cost of layer production Energy
gain has to exceed cost of maintenance.
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• Fate of fixed carbon
• ca. 50 of fixed C goes into cellular respiration
• But, varies with amount of non-photosynthetic
  tissue
• Growth of roots, stems, leaves, varied to
  maximize commodity acquisition in a changing
  environment.
• Determining pattern of world productivity
• Satellite imagery spectral reflectance sensors
• Terrestrial ecosystems
• Photosynthesis produces a unique reflectance
  pattern of visible and near infrared wavelengths.
• Converted to an intensity scale closely related
  to primary production.
• Aquatic ecosystems
• Blue/green ratios

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Terrestrial productivity (5 yr.)