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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: - CO 2 assimilation rate exceeds respiration rate Seasonal Variation in Temperate Environments
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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 prairie grassland What causes the Midday minimum in August?
NEE = A + R A = Gross Photosynthesis (-) R = Total Ecosystem Respiration (+)
Night-time NEE = Total Ecosystem Respiration Mer Bleue Bog, Eastern Ontario NEE (mol CO2m-2s-1) Soil Temperature at 5cm depth (C)
Daytime NEE Gross Photosynthesis – Total Ecosystem Respiration NEE (mol CO2m-2s-1) Photosynthetically-active radiation (molm-2s-1)
Fluxnet-Canada Carbon Flux Stations Balsam fir Coastal conifers Eastern peatland Southern boreal conifers and hardwoods Western peatland Boreal mixedwood