Measurements of CO2 exchange at the forest floor were made in shady dry areas dominated by feather mosses and open wet areas dominated by Sphagnum mosses within a 120-year-old black spruce forest in central Saskatchewan during 1996. Our objective was to study the environmental regulation of moss photosynthesis and forest floor (moss and soil) respiration,… More

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This paper shows the results of solar flux measurements routinely collected within boreal conifer forests during BOREAS 1994. Such vegetation have open canopies with a high level of clumping and covered by crowns which yields strong directional effects on the spectral hemispherical transmittances, as well as absorbed PAR. The crown intercepts the light more effectively… More

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Root biomass, net primary production and turnover were studied in aspen, jack pine and black spruce forests in two contrasting climates. The climate of the Southern Study Area (SSA) near Prince Albert, Saskatchewan is warmer and drier in the summer and milder in the winter than the Northern Study Area (NSA) near Thompson, Manitoba, Canada…. More

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We used eddy covariance to measure the net exchange of CO2 between the atmosphere and a black spruce (Picea mariana) forest in Manitoba for 16,500 hours from March 16, 1994 to October 31, 1996. We then partitioned net exchange into gross photosynthesis and respiration by estimating daytime respiration as a function of temperature, and used… More

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We investigated controls over the emission of monoterpenes from two species of boreal forest conifers, black spruce (Picea mariana Miller (B.S.P.)) and jack pine (Pinus banksiana Lamb). Monoterpenes are important in plants as carbon-based defensive compounds and in the atmosphere as photochemically reactive compounds that affect ozone and carbon monoxide concentrations. We examined ecological theories… More

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A process-based, general ecosystem model (BIOME–BGC) was used to simulate daily gross primary production, maintenance and heterotrophic respiration, net primary production and net ecosystem carbon exchange of boreal aspen, jack pine and black spruce stands. Model simulations of daily net carbon exchange of the ecosystem (NEE) explained 51.7% (SE = 1.32 g C m−2 day−1)… More

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To gain insight into the function of photosynthesis and respiration as processes operating within a global ecosystem, we measured gas exchange of mature black spruce (Picea mariana (Mill.) B.S.P.) trees at three organizational scales: individual shoots, whole branches and a forest canopy. A biochemical model was fitted to these data, and physiological parameters were extracted…. More

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Black spruce (Picea mariana [Mill.] BSP) is the most dominant forest ecosystem in the North American boreal region. There are at least two contrasting boreal black spruce forest communities: open-canopy black spruce overstory with Sphagnum ground cover (BSSP) and closed-canopy black spruce overstory with feathermoss ground cover (BSFM). The objectives of this study were (a)… More

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Soil surface CO2 flux (RS) is overwhelmingly the product of respiration by roots (autotrophic respiration, RA) and soil organisms (heterotrophic respiration, RH). Many studies have attempted to partition RS into these two components, with highly variable results. This study analyzes published data encompassing 54 forest sites and shows that RA and RH are each strongly… More

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