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 lichenCladonia rangiferina

Solar Energy and Productivity

• The overall rate of this conversion is calledGross 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

AUTOTROPHS:• photosynthetic• chemosyntheti

c

Plants, algae,cyanobacteria

FirstTrophicLevel

SecondTrophic

level

ThirdTrophicLevel

FourthTrophicLevel

HETEROTROPHS

Feed on other animals

(2° and up)

Feed on plants (1° consumers)

Animalbio-

mass

Plant biomass

5 - 20% of biomass

passesbetween

levels

5 - 20%

5 - 20%

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

• Hydrologic (water) cycle• Geologic (rock) cycle

• Carbon cycle• Nitrogen cycle• Phosphorus cycle

include

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