Soils contain about twice as much carbon as Earth’s atmosphere, so their response to warming is crucial to understanding carbon fluxes in a changing climate. Past studies have heated soil to a depth of 5 to 20 cm to examine such fluxes. Hicks Pries et al. heated the ground to a depth of 100 cm…. More

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During the summer of 2001, NO2, total peroxy nitrates (ΣPNs), total alkyl nitrates (ΣANs), HNO3, volatile organic compounds (VOC), CO2, O3, and meteorological variables were measured at Granite Bay, CA. The diurnal variation in ΣPNs, ΣANs and HNO3 were all strongly correlated with sunlight, indicating both that they are photochemically produced and that they have… More

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Ponderosa pine is one of the most sensitive species to ozone and a dominant species in the Sierra Nevada Mountains. To assess the factors controlling ozone deposition to the forest and to study the forest response, we established a research site in a ponderosa pine plantation ∼75 km northeast of Sacramento. Ozone concentration and ozone… More

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The largest biological fractionations of stable carbon isotopes observed in nature occur during production of methane by methanogenic archaea. These fractionations result in substantial (as much as ≈70‰) shifts in δ13C relative to the initial substrate. We now report that a stable carbon isotopic fractionation of comparable magnitude (up to 70‰) occurs during oxidation of… More

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Differences in the seasonal pattern of assimilatory and respiratory processes are responsible for divergences in seasonal net carbon exchange among ecosystems. Using FLUXNET data (http://www.eosdis.ornl.gov/FLUXNET) we have analyzed seasonal patterns of gross primary productivity (FGPP), and ecosystem respiration (FRE) of boreal and temperate, deciduous and coniferous forests, Mediterranean evergreen systems, a rainforest, temperate grasslands, and… More

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Mixing ratios and emission rates of monoterpenes were measured above a ponderosa pine plantation in the Sierra Nevada mountains before, during and after a pre-commercial thinning in spring 2000. The thinning removed and left onsite approximately one half of the plantations biomass. Monoterpene fluxes increased tenfold during the thinning and pinene mixing ratios in excess… More

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Observations of isoprene and its oxidation products methacrolein (MACR) and methyl vinyl ketone (MVK) are used to quantify the impact of isoprene oxidation on ozone production along the western slope of the Sierra Nevada mountains. Regular daytime up-slope wind flow patterns transport anthropogenic volatile organic compounds (VOC) and NOx emissions from the Central Valley toward… More

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Acetone was one of the most abundant volatile organic compounds (VOCs) observed in the Sierra Nevada Mountains (California, USA). Mixing ratios were measured hourly above a ponderosa pine plantation using an automated in situ dual-channel GC-FID system throughout July 1997, from July through October 1998, and fluxes were measured with a relaxed eddy accumulator from… More

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