ECOSYSTEM ECOLOGY

(For example, as organisms do work, they use energy, and must continue to take in additional fuel to continue doing work.)

Energy Flow begins with PRIMARY PRODUCTIVITY, the amount of light energy converted to chemical energy (stored in organic molecules) by an ecosystem's autotrophs over a given period of time via the process of PHOTOSYNTHESIS.

• GROSS Primary Productivity (GPP) - Total primary productivity

• RESPIRATION (R) - Energy used to do work in the organism (lost as entropy)

• NET Primary Productivity (NPP) - Total primary productivity less the

  energy used for respiration

Primary productivity (always expressed as a RATE) can be expressed as

• ENERGY per unit area per unit time (e.g., Joules/m²/year)

  or

• BIOMASS, the dry weight of vegetation added to an ecosystem per unit area per unit time (e.g., grams/m²/year).

Energy flow is never 100% efficient, and this results in the classic Pyramid of Productivity.

The efficiency with which trophic levels convert energy from the previous trophic levels varies greatly with ecosystem, and usually range between 5% - 20% (What does this mean in terms of how much is LOST at each trophic level?), as reflected by the STANDING CROP BIOMASS of each level.

In a few ecosystems, there are some surprises!

Biogeochemical Cycles

...can be superimposed on Biogeochemical Cycles for various substances...

• The Water Cycle
• The Carbon Cycle
• The Nitrogen Cycle
• The Phosphorus Cycle
• ...and any other element.

Go forth and spread the word.