Ch. 3 Ecosystems
GPP & NPP
The amount of energy
available in an
ecosystem determines how much
life an ecosystem
can support.
Some ecosystems produce plant matter faster than others do
Variation in productivity on EarthHigh productivity -- greenLow productivity -- yellow
Estuaries
Swamps and marshes
Tropical rain forest
Temperate forest
Northern coniferous forest (taiga)
Savanna
Agricultural land
Woodland and shrubland
Temperate grassland
Lakes and streams
Continental shelf
Open ocean
Tundra (arctic and alpine)
Desert scrub
Extreme desert
800 1,600 2,400 3,200 4,000 4,800 5,600 6,400 7,200 8,000 8,800 9,600
Average net primary productivity (kcal/m2/yr)
Fig. 4.25, p. 88
Estimated annual average of NPP per unit area in major life zones and ecosystems
Converting Sunlight into Chemical Energy is NOT Efficient
Gross Primary Productivity• Gross Primary
Productivity (GPP) - Rate at which an ecosystem’s producers convert solar energy into chemical energy as biomass • GROSS = TOTAL
Net Primary Productivity
• The rate at which energy for use by consumers is stored in new biomass (cells, leaves, roots, and stems)
• UNITS – Units of energy (Kcal) or biomass
available/specified area (m2)/given time
Net Primary Productivity
Net Primary Productivity (NPP)
Rate at which producers store energy as biomass (produced by photosynthesis)
Rate at which producers use chemical energy stored as biomass (through aerobic respiration)
= _
GPP & NPP
FORMULAS
• GPP = NPP + Respiration• NPP = GPP – Respiration• Respiration = GPP - NPP
ANALOGY
• GPP = Paycheck• NPP = Amount take home• Respiration = Taxes
Practice
• The net primary productivity of an ecosystem is 1 kg C/m2/year, and the energy needed by the producers for their own respiration is 1.5 kg C/m2/year. The gross primary productivity of such an ecosystem would be ________________.2.5 kg C/m2/year
Practice
• The GPP of an ecosystem is 3 kg C/m2/year and 0.5 kg C/m2/year is used for respiration. What is the NPP of this ecosystem?
2.5 kg C/m2/year
Why do we care about productivity?
• NPP limits the number of consumers that can survive on earth
• Measuring tool of biosphere production
• Can be used to measure human impact
NPP Lab
Hints for the Lab
• Dissolved Oxygen (DO) = Concentration of dissolved oxygen in water/air
Calculating GPP Indirectly
Nomogram: water temperature, Oxygen mg/L, % Saturation
Top Related