Post on 30-Dec-2015
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Plant Canopies and Carbon Dioxide Flux
At night: - flux directed from canopy to the atmosphere- respiration from leaves, plant roots, soil
Daytime: - CO2 assimilation rate exceeds respiration rate
Seasonal Variation in Temperate Environments
Spring: Assimilation increases with leaf area index and increasing solar radiation availability/day length
Midsummer: Fc drops despite sun, due to soil moisture depletion – flux higher in morning
Winter: Small, negative flux
Vertical flux of carbon dioxide(FC) over a prairiegrassland
What causes theMidday minimum in August?
Notice how low the CO2 concentration was in 1969 !
NEE = A + R
A = Gross Photosynthesis (-)
R = Total EcosystemRespiration (+)
NEE = 0.1223 (soil temp) - 0.0525
R2 = 0.2477
-10
-8
-6
-4
-2
0
2
4
6
8
10
0 5 10 15 20 25 30
Night-time NEE = Total Ecosystem RespirationN
EE
(m
ol C
O2
m-2s
-1)
Soil Temperature at 5cm depth (C)
Mer Bleue Bog,Eastern Ontario
-12
-8
-4
0
4
8
0 1000 2000
Daytime NEE Gross Photosynthesis – Total Ecosystem Respiration
NE
E (m
ol C
O2
m-2s
-1)
Photosynthetically-active radiation (molm-2s-1)
Fluxnet-Canada Carbon Flux Stations
Coastal conifers
Southern boreal conifers and hardwoods Boreal
mixedwood
Balsam fir
Eastern peatlandWestern
peatland
CO2 richDry, Cool
Low CO2
Humid, Warm