The eddy covariance technique is the most common method of measuring forest evapotranspiration directly. Evapotranspiration can also be estimated by solving for the residual of the energy balance measurements of net radiation, sensible heat flux density and ground heat flux density. However, the lack of energy balance closure of all components creates uncertainty in using… More

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Fire in the boreal forest renews forest stands and changes the ecosystem properties. The successional stage of the vegetation determines the radiative budget, energy balance partitioning, evapotranspiration and carbon dioxide flux. Here, we synthesize energy balance measurements from across the western boreal zone of North America as a function of stand age following fire. The… More

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Disturbances are important for renewal of North American forests. Here we summarize more than 180 site years of eddy covariance measurements of carbon dioxide flux made at forest chronosequences in North America. The disturbances included stand-replacing fire (Alaska, Arizona, Manitoba, and Saskatchewan) and harvest (British Columbia, Florida, New Brunswick, Oregon, Quebec, Saskatchewan, and Wisconsin) events,… More

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Disturbances by fire and harvesting are thought to regulate the carbon balance of the Canadian boreal forest over scales of several decades. However, there are few direct measurements of carbon fluxes following disturbances to provide data needed to refine mathematical models. The eddy covariance technique was used with paired towers to measure fluxes simultaneously at… More

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Four large cuvettes were used to measure whole-branch CO2 and H2O vapour exchange at the Boreal Ecosystem-Atmosphere Study, Southern Study Area, Old Black Spruce site. Measurements started before the spring thaw and continued until after the winter freeze-up. Daytime photosynthesis, nighttime respiration, transpiration rate, and branch conductances were zero at the start and the end… More

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Recent CO2 flux measurements from towers and aircraft (net ecosystem exchange by eddy covariance) and remote sensing/modeling (net primary productivity—NPP) following fire show that the regenerating boreal forest in western Canada has a low initial flux that increases with time since fire. Daytime CO2 fluxes are downward, even after 2 years following fire, although fluxes… More

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Fire and harvesting are major forest renewal processes in the Canadian boreal forest. The eddy covariance method was used to compare ecosystem fluxes of carbon dioxide between harvested and burned boreal forest sites in Saskatchewan, Canada. The harvest chronosequence had sites harvested in 2002 (HJP02), 1994 (HJP94) and 1975 (HJP75), whereas the fire chronosequence sites… More

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Fire and harvesting are important disturbances in the boreal forest, driving net biome production. Measurements of net ecosystem production (NEP) over mature forest stands have been made from flux towers for about a decade at the Boreal Ecosystem Research and Monitoring Sites (BERMS) in central Saskatchewan, Canada. Over the last few years, the network of… More

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Annual net ecosystem production (NEP) was estimated at three boreal forest sites where open-path infrared gas analysers were used in eddy covariance systems. The analysers showed apparent ecosystem uptake of carbon dioxide during frozen conditions where small net respiration was expected. Previous studies have shown this to be largely caused by instrument heating creating an… More

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