A gaseous deposition model, based on a realistic canopy stomatal resistance submodel, is described, analyzed and tested. This model is designed as one of a hierarchy of simulations, leading up to a “big-leaf” model of the processes contributing to the exchange of trace gases between the atmosphere and vegetated surfaces. Computations show that differences in… More

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Future climate change is expected to affect ecosystem-atmosphere CO2 exchange, particularly through the influence of temperature. To date, however, few studies have shown that differences in the response of net ecosystem CO2 exchange (NEE) to temperature among ecosystems can be explained by differences in the photosynthetic and respiratory processes that compose NEE. Using a new… More

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In summer 1992, isoprene emission was measured on intact leaves and branches of Quercus alba (L.) at two heights in a forest canopy. Isoprene emission capacity (measured at 30 °C and a photosynthetic photon flux density of 1000 μmol m−2 s−1) was significantly higher in sun leaves than in shade leaves when expressed on a… More

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Individual rain events were sampled above and below the forest canopy in Walker Branch Watershed, Tennessee, from August 1977 to June 1978 for the purpose of analysis of acidity and organic content. Strong acid content correlated with sulfate concentrations. Total acid concentrations were conserved as rain penetrated chestnut oak (Quercus prinus L.) canopies, although the… More

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The seasonal variability in the frequency distribution (FD) and higher order moments (e.g., standard deviation, skewness and kurtosis) of photosynthetically active radiation (PAR) penetration in an oak—hickory forest were examined. In a leafless, wintertime forest the FD is unimodal and skewed. In a leafing forest, the FD is highly variable and is strongly skewed. This… 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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Global shortwave, photosynthetically active, net and allwave radiation was measured above, and at several levels within an oak—hickory forest with instruments mounted on a moving tram system. Profiles of radiation flux densities were quantified using extinction coefficients based on the Beer—Bouguer law. Data are reported here from periods when the forest was both fully-leafed and… More

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