Primary productivity refers to the conversion of light energy to chemical energy through photosynthesis by autotrophs. There are three main types of primary productivity: gross primary productivity, respiration, and net primary productivity. Primary productivity can be expressed as either the energy captured per unit area per time, or the biomass produced per unit area per time. Standing crop biomass refers to the dry weight of vegetation at a moment in time, not a rate like primary productivity. Energy flow through ecosystems is inefficient, forming a pyramid of productivity where the majority of energy is lost at each trophic level. Biogeochemical cycles recycle nutrients through different components of the Earth system, moving substances through air, water, soil, rocks and organisms.

1. ProductivityProductivityProductivityProductivity
• Energy Flow begins with PRIMARYPRIMARYPRIMARYPRIMARY PRODUCTIVITYPRODUCTIVITYPRODUCTIVITYPRODUCTIVITY, 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.
• GROSSGROSSGROSSGROSS PrimaryPrimaryPrimaryPrimary ProductivityProductivityProductivityProductivity (GPP)(GPP)(GPP)(GPP) - Total primary productivity
• RESPIRATIONRESPIRATIONRESPIRATIONRESPIRATION (R)(R)(R)(R) - Energy used to do work in the organism (lost
as entropy)
• NETNETNETNET PrimaryPrimaryPrimaryPrimary ProductivityProductivityProductivityProductivity (NPP)(NPP)(NPP)(NPP) - Total primary productivity less
the
energy used for respiration

2. Primary productivity (always expressed as a RATE) can be expressed as
• ENERGYENERGYENERGYENERGY per unit area per unit time (e.g., Joules/m2
/year)
or
• BIOMASSBIOMASSBIOMASSBIOMASS, the dry weight of vegetation added to an ecosystem per
unit area per unit time (e.g., grams/m2
/year).
STANDINGSTANDINGSTANDINGSTANDING CROPCROPCROPCROP BIOMASSBIOMASSBIOMASSBIOMASS is the dry weight of vegetation in an
ecosystem at any given "snapshot moment" in time. It is not the same as
primary productivity: it's not a rate!Energy flow is never 100% efficient.
This results in a pyramidpyramidpyramidpyramid ofofofof productivityproductivityproductivityproductivity.
The efficiency with which trophic levels convert energy from the previous
trophic levels varies among ecosystems, but usually range between 5% -
20%.
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next!next!next!next!

3. BiogeochemicalBiogeochemicalBiogeochemicalBiogeochemical CyclesCyclesCyclesCycles
Globlal cycles recycle nutrients through the erath's air, water, soil, 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,rocks and living organisms.
A generalized cycle...

4. ...can be superimposed on Biogeochemical Cycles for various substances...
• The Water Cycle

5. • The Carbon Cycle

6. • The Nitrogen Cycle

7. • The Phosphorus Cycle
Your activities any day have profound effects on these cycles, and on
energy cycling in the biosphere.