Solar Energy and Productivity
TREN 1F90:
Sustainability, Environment and Tourism
Solar Energy and Productivity
• Average annual solar energy input to the
surface of the earth is about
1.5 x 106 kcal / m2 / year
• Primary producers convert solar energy
into potential energy of chemical bonds in
their tissues through photosynthesis
Arctic ice diatoms:
Melosira arctica
Young oak seedling
Quercus sp. on forest floor
Reindeer “moss”: the lichen
Cladonia rangiferina
Solar Energy and Productivity
• The overall rate of this conversion is called
Gross Primary Productivity (GPP)
• Subtracting the amount of energy required
for cellular maintenance and respiration of
the primary producer yields
Net Primary Productivity (NPP)
GPP – (respiration and maintenance) = NPP
Productivity in different ecosystems
• Productivity and biomass production vary
widely in different biomes
• Most productive environments per unit area:
wetlands and estuaries
• Least productive environments per unit area:
deserts and open ocean
Energy and Trophic Levels
Energy and Trophic Levels
HETEROTROPHS
Feed on
other animals
(2° and up)
Plants, algae,
cyanobacteria
Fourth
Trophic
Level
Third
Trophic
Level
Feed on plants
(1° consumers)
Second
Trophic
level
AUTOTROPHS:
•photosynthetic
•chemosynthetic
First
Trophic
Level
5 - 20%
5 - 20%
Animal
biomass
Plant biomass
5 - 20%
of biomass
passes
between
levels
Energy for growth and metabolism
Energy and nutrient flow in an ecosystem
Energy and nutrient flow in an ecosystem
Food webs
• Complex and
difficult to
diagram
• A given
organism may
function at one
trophic level
or multiple
trophic levels at
the same time
Simplified elements of a food web in Lake Erie
Biogeochemical cycles
Prominent
include
• Hydrologic (water) cycle
• Geologic (rock) cycle
• Carbon cycle
• Nitrogen cycle
• Phosphorus cycle
Hydrologic cycle
and land
Groundwater
Geologic (rock) cycle
Major elements of a nutrient cycle
for a defined ecosystem
Source: Modified from Likens et al. (1977)
Elements of the global carbon cycle
Units: billions of tonnes of carbon (109 t)
Fluxes between compartments are in 109 t/y.
Sources: Blasing (1985), Solomon et al. (1985), and Freedman (1995)
Global carbon cycle - simplified
Nitrogen cycle
Phosphorus cycle