Ecologists are expected to play an important role in future studies of the biosphere/atmosphere exchange of materials associated with the major biogeochemical cycles and climate. Most studies of material exchange reported in the ecological literature have relied on chamber techniques. Micrometeorological techniques provide an alternative means of measuring these exchange rates and are expected to… More

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The penetration of diffuse sky radiation via canopy opening into a fully-leafed tulip poplar forest was estimated from canopy structure data obtained from canopy photographs and from sky brightness distribution approximations, using techniques originally developed by Anderson (1964). Small differences were found among mean daily penetration fractions predicted assuming an isotropic sky (UOC), a standard… More

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Soil hydraulic properties at eight depths in a Fullerton cherty silt loam (a clayey, kaolinitic, thermic Typic Paleudult) profile were derived from measurements of water content with a calibrated neutron probe and of matric potential with tensiometers during drainage of a flooded 2- by 2- by 3-m deep soil plot. Soil cores taken from the… More

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Estimates of forest net primary production (NPP) demand accurate estimates of root production and turnover. We assessed root turnover with the use of an isotope tracer in two forest free-air carbon dioxide enrichment experiments. Growth at elevated carbon dioxide did not accelerate root turnover in either the pine or the hardwood forest. Turnover of fine… More

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Forests in the south-eastern United States experienced a prolonged dry spell and above-normal temperatures during the 1995 growing season. During this episode, nearly continuous, eddy covariance measurements of carbon dioxide and water vapour fluxes were acquired over a temperate, hardwood forest. These data are used to examine how environmental factors and accumulating soil moisture deficits… More

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A study of carbon cycling within the floor of a mixed deciduous forest included estimates of litterfall, litter standing crop, root turnover, lateral root standing crop, and measurements of gaseous carbon losses from the various components. Annual carbon inputs to the system were 161 g C ° m—2 as litterfall and 733 g C °… More

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We used gas exchange techniques to estimate maximum rate of carboxylation (Vcmax), a measure of photosynthetic capacity, in the understory and upper crown of a closed deciduous forest over two seasons. There was extensive variability in photosynthetic capacity as a result of vertical canopy position, species type, leaf age and drought. Photosynthetic capacity was greater… More

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Long-term and direct measurements of CO2 and water vapour exchange are needed over forested ecosystems to determine their net annual fluxes of carbon dioxide and water. Such measurements are also needed to parameterize and test biogeochemical, ecological and hydrological assessment models. Responding to this need, eddy covariance measurements of CO2 and water vapour were made… More

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