Movement of Energy in Ecosystems
Lesson objectives
•
Understand how energy moves through an ecosystem
•
Describe different ways to measure productivity
•
Compare net productivity among different ecosystems
•
Understand how nutrients can affect productivity
•
Calculate trophic efficiencies
•
Solar energy powers
photosynthesis of producers
•
Few ecosystems use chemical
energy for chemosynthesis
•
Producers form base of food webs
The sun is the ultimate source of energy
for most ecosystems
1% of solar energy is captured
•
Gross primary productivity
(GPP)
rate that energy is captured and
assimilated by producers
•
Energy used for respiration,
growth, reproduction
•
Net primary productivity
(NPP)
rate that energy is assimilated
into producer biomass
•
Standing crop
•
NPP = GPP - respiration
Primary productivity is the rate at which energy is
converted into organic compounds in producers
GPP = 2.5 kg C/m
2
/yr
Respiration = 1.5 kg C/m
2
/yr
NPP = 1 kg C/m
2
/yr
How can primary productivity be quantified?
Producer
biomass
Remote
sensing
Uptake/Release of
CO
2
or O
2
Light-dark bottle experiments
NPP = net CO
2
GPP = net CO
2
+ respired CO
2
Terrestrial vs Aquatic
NPP =
net O
2
GPP = net O
2
+ respired O
2
NPP = GPP - respiration
GPP
-
R
+
GPP
-
R
GPP = NPP + respiration
R
