Interdisciplinary field experiments for global change research are large, intensive efforts that study the controls on fluxes of carbon, water, trace gases, and energy between terrestrial ecosystems and the atmosphere at a range of spatial scales. Forest ecophysiology can make significant contributions to such efforts by measuring, interpreting, and modeling these fluxes for the individual… More

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We measured stem respiration rates during and after the 1994 growing season of three common boreal tree species at sites near the northern and southern boundaries of the closed-canopy boreal forest in central Canada. The growth respiration coefficient (rg; carbon efflux per μmole of carbon incorporated in structural matter) varied between 0.25 and 0.76, and… More

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Area-averaged fluxes are constructed from a combination of aircraft and tower data collected during BOREAS. The averaging area includes both conifer and deciduous forests, wetlands, burned areas and bodies of water. The area-averaged water vapour flux is closely related to the area-averaged solar radiation while the area-averaged carbon dioxide flux and water use efficiency (WUE)… More

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Fluxes of energy and water vapor over boreal forest stands are expected to vary during the growing season due to temporal variations in solar energy, soil and air temperature, soil moisture, photosynthetic capacity, and leaf area. To investigate this hypothesis, we measured fluxes of energy balance components (solar, latent and sensible heat, and soil and… More

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We used field measurements and Monte Carlo simulations of canopy gap-size distribution and gap fraction to examine how beam radiation interacts with clumped boreal forest canopies of aspen (Populus tremuloides Michx.), black spruce (Picea mariana (Mill.) B.S.P.) and jack pine (Pinus banksiana Lamb.). We demonstrate that the Beer-Lambert law can be modified to accommodate transmission… More

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A new approach is presented for deriving vegetation canopy structural characteristics from hyperspectral bidirectional reflectance distribution function (BRDF) data. The methodology is based on the relationship between spectral variability of BRDF effects and canopy geometry. Tests with data acquired with the Advanced Solid-State Array Spectroradiometer (ASAS) over Canadian boreal forests during the BOREAS campaign show… More

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We calculated carbon budgets for a chronosequence of harvested jack pine (Pinus banksiana Lamb.) stands (0-, 5-, 10-, and∼29-year-old) and a∼79-year-old stand that originated after wildfire. We measured total ecosystem C content (TEC), above-, and belowground net primary productivity (NPP) for each stand. All values are reported in order for the 0-, 5-, 10-, 29-,… More

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We measured seasonal and canopy-level gas exchange in two stands of jack pine (Pinus banksianaLamb.) and one stand of black spruce (Picea mariana (Mill.) B.S.P.) on relatively clear days from late May until mid-September 1994. Field measurements were made with a portable infrared gas analyzer, and laboratory measurements included photosynthetic oxygen evolution and needle chemical… More

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Monitoring of forest evolution and functioning with remote sensing depends on canopy BRF (bidirectional reflectance factor) sensitivity to biophysical parameters and to canopy PAR (photosynthetically active radiation) regime. Here, we study the canopy BRF of a tropical (Sumatra) and three boreal (Canada) forest sites, with the DART (discrete anisotropic radiative transfer) model. The behavior of… More

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