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Rising atmospheric CO2 may stimulate future forest productivity, possibly increasing carbon storage in terrestrial ecosystems, but how tropospheric ozone will modify this response is unknown. Because of the importance of fine roots to the belowground C cycle, we monitored fine-root biomass and associated C fluxes in regenerating stands of trembling aspen,(More)
The Intergovernmental Panel of Climate Change (IPCC) has concluded that the greenhouse gases carbon dioxide (CO2) and tropospheric ozone (O3) are increasing concomitantly globally. Little is known about the effect of these interacting gases on growth, survival, and productivity of forest ecosystems. In this study we assess the effects of three successive(More)
Over the years, a series of trembling aspen (Populus tremuloides Michx.) clones differing in 03 sensitivity have been identified from OTC studies. Three clones (216 and 271[(03 tolerant] and 259 [Os sensitive]) have been characterized for Or sensitivity by growth and biomass responses, foliar symptoms, gas exchange, chlorophyll content, epicuticular wax(More)
Abbreviations: A, light-saturated photosynthesis at ambient [CO2]; Ca, ambient CO2 concentration; Ci, intercellular CO2 concentration; gs, stomatal conductance; ls, relative stomatal limitation; LPI, leaf plastochron index; r*, cotangent of A–Ci curve at the operating [CO2]; rbl, boundary layer resistance; rs, stomatal resistance (1/gs); Rubisco,(More)
Human activity causes increasing background concentrations of the greenhouse gases CO2 and O3. Increased levels of CO2 can be found in all terrestrial ecosystems. Damaging O3 concentrations currently occur over 29% of the world's temperate and subpolar forests but are predicted to affect fully 60% by 2100 (ref. 3). Although individual effects of CO2 and O3(More)
Atmospheric chemical composition affects foliar chemical composition, which in turn influences the dynamics of both herbivory and decomposition in ecosystems. We assessed the independent and interactive effects of CO2 and O3 fumigation on foliar chemistry of quaking aspen (Populus tremuloides) and paper birch (Betula papyrifera) at a Free-Air CO2 Enrichment(More)
To determine whether elevated CO2 reduces or exacerbates the detrimental effects of O3 on aspen (Populus tremuloides Michx.). aspen clones 216 and 271 (O3 tolerant), and 259 (O3 sensitive) were exposed to ambient levels of CO2 and O3 or elevated levels of CO2, O3, or CO2 + O3 in the FACTS II (Aspen FACE) experiment, and physiological and molecular responses(More)
1736–1991, there is no statistically significant correlation between them. The complex relationship between the Mount Logan time series, the PNA and the PDO identified in this paper is not unique. For example, the correlation between salmon productivity in Alaska and the PDO, although robust over the past 50 years, shows changes in correlation and phase(More)
The United States and Canada currently use exposure-based metrics to protect vegetation from O(3). Using 5 years (1999-2003) of co-measured O(3), meteorology and growth response, we have developed exposure-based regression models that predict Populus tremuloides growth change within the North American ambient air quality context. The models comprised(More)
Impacts of elevated atmospheric O3 and/or CO2 on three clones of aspen (Populus tremuloides Michx.) and birch (Betula papyrifera Marsh.) were studied to determine, whether or not elevated CO2 ameliorates O3-induced damage to leaf cells. The plants were exposed for 3 years at the Aspen FACE exposure site in Wisconsin (USA) prior to sampling for(More)