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17 Cards in this Set

  • Front
  • Back
Primary Production in an Ecosystem (definition)
the amount of light energy converted to chemical energy by autotrophs during a given time period. Examples include carbon fixing and photosynthesis.
Gross Primary Productin(GPP)/Net Primary Production (NPP)
GPP: Total primary production in an ecosystem. (Total amount of carbon converted to glucose) 2% of solar energy hits photosynthetic organisms. Half of that (1%) lost in respiration, leaving:::

NPP: Total amount of primary production that occurs by primary producers. NPP is the energy available to primary consumers after 1% lost to respiration. NPP is the amount of plant biomass in an ecosystem.
NPP by Biome:
Biome Size:::
Largest- Open Ocean
Smallest - Algal Zones and reefs

NPP by size ratio::
Largest: Algal zones/reefs, tropical rain forests, marshes
Smallest: Extreme Ice/desert/rock

Total NPP of Earth:::
Largest: Open Ocean, tropical Rain Forest
Smallest: Upwelling zones, lakes/streams
Aquatic Primary Production Limited by:
Nutrients and Light penetration. Most important is Nutrients. Limited by Phosphorus and Nitrogen.

Negative feedback between primary productivity and light penetration. As productivity goes up, light penetration goes down.

Recall experiment: When ammonium was added to control group, production skyrocketed.
Increasing productivity of water body through nutrient addition.
Terrestrial primary production Limitations:
Limited by temperature and moisture. (as well as nutrient cycling). Cold, dry = less productive.

Evapotranspiration--Amount of water annually transpired by plants and evaporated from landscape. Related to NPP.
Secondary production
Amount of chemical energy in consumers' food that is converted to their own new biomass during a given period.
Production efficiency
Energy txfer between trohpic levels is usually less than 20% efficient. (Remember 10% E remains from one level to next)

When a caterpillar feeds on a leaf, only about one-sixth of the energy is used for secondary production.
"Green World Hypothesis"
Terrestrial herbivores consume relatively little plant biomass because they are held in check by predators.

Called top-down control.
Factors beyond Green World Hypothesis
Plants have defenses (tannins, thorns)

Nutrients, not energy supply, limit herbivores.

Herbivore populations are limited by abiotic, intraspecific, and interspecific mechanisms.
Biological and Chemical processes move nutrients between organic (consumers) and inorganic (plants) parts of the ecosystem.

Water, Carbon, and Nitrogent cycle on a global scale. Phosphorus cycles on a local scale.
Nutrient Cycles
Water: Cycle driven primarily by solar energy/Physics/abiotic influence. Polar ice caps a significant recalcitrant form of water. Aquifer is another minor form.

Carbon: Atmospheric, converted by plants, consumed, respirated back to atmosphere or stacked in deep ocean. Photosynthesis and Cellular respiration.

Nitrogen:Starts as N2 in atmosphere. Cannot be fixed by plants/animals. Nitrogen-fixing bacteria in the soil convert to ammonia, used by producers/consumers. Nitrifying bacteria convert to NO2/NO3, denitrifying bacteria return it to atmospheric N2. Most nitro cycling involves local cycling between organisms and soil/water. Most urine is nitrogenous waste and is mildly toxic.

Phosphorus: No atmospheric portion. Weathering rocks, runoff, rain, consumption. Plants uptake phosphate. Phosphorus is perpetually declining in any given ecosystem.
Hubbard Brook Experimental Forest
Used to study nutrient cycling since 1963.

Giant rings that sprayed CO2 and they monitored plant growth to determine correlation.

Conducted deforestation experiment. In cleared area, Nitrogen runoff (loss) was exponential.
Rate of nutrient cycling determined by
The rates at which nutrients cycle in different ecosystems vary widely, mostly as a result of differences in rates of decomposition (by Detritivores).

Rate of decomposition is affected by moisture, temperature, and nutrient levels. Colder, Drier = slower.

Also vegetation: Natural vegetation results in faster cycling and less loss of nutrients.
Main nutrient lost through agriculture
Nitrogen. Anthropogenic nitrogen (soil additives/fertilizer) accounts for 27% of the nitrogen on earth.
Acid Rain
Caused by combustion of fossil fuels, which release sulfer and Nitrogen. Forms nitric and sulfuric acid in the atmoshpere.
Biological Magnification
Toxins concentrate at higher trophic levels.