Joseph N T Darbah

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Paper birch (Betula papyrifera Marsh.) and three trembling aspen clones (Populus tremuloides Michx.) were studied to determine if alterations in carbon gain in response to an elevated concentration of CO(2) ([CO(2)]) or O(3) ([O(3)]) or a combination of both affected bud size and carbohydrate composition in autumn, and early leaf development in the(More)
We studied the effects of long-term exposure (nine years) of birch (Betula papyrifera) trees to elevated CO(2) and/or O(3) on reproduction and seedling development at the Aspen FACE (Free-Air Carbon Dioxide Enrichment) site in Rhinelander, WI. We found that elevated CO(2) increased both the number of trees that flowered and the quantity of flowers (260%(More)
The effect of high temperature on photosynthesis of isoprene-emitting (aspen) and non-isoprene-emitting (birch) trees were measured under elevated CO(2) and ambient conditions. Aspen trees tolerated heat better than birch trees and elevated CO(2) protected photosynthesis of both species against moderate heat stress. Elevated CO(2) increased carboxylation(More)
Atmospheric CO2 and tropospheric O3 are rising in many regions of the world. Little is known about how these two commonly co-occurring gases will affect reproductive fitness of important forest tree species. Here, we report on the long-term effects of CO2 and O3 for paper birch seedlings exposed for nearly their entire life history at the Aspen FACE (Free(More)
Photosynthetic acclimation under elevated carbon dioxide (CO(2)) and/or ozone (O(3)) has been the topic of discussion in many papers recently. We examined whether or not aspen plants grown under elevated CO(2) and/or O(3) will acclimate after 11 years of exposure at the Aspen Face site in Rhinelander, WI, USA. We studied diurnal patterns of instantaneous(More)
The diurnal changes in light-saturated photosynthesis (Pn) under elevated CO(2) and/or O(3) in relation to stomatal conductance (g(s)), water potential, intercellular [CO(2)], leaf temperature and vapour-pressure difference between leaf and air (VPD(L)) were studied at the Aspen FACE site. Two aspen (Populus tremuloides Michx.) clones differing in their(More)
We studied the effect of high ozone (O(3)) concentration (110-490 nmol mol(-1)) on regenerating aspen (Populus tremuloides) and maple (Acer saccharum) trees at an open-air O(3) pollution experiment near Rhinelander WI USA. This study is the first of its kind to examine the effects of acute O(3) exposure on aspen and maple sprouts after the parent trees,(More)
Introduction The concentration of CO2 in the atmosphere has risen by approximately 35% since the pre-industrial era to approximately 380 ppm, now, and is continuing to rise by 1-2 ppm per year. This rate of CO2 increase in the atmosphere is unprecedented in the recent past, for at least two million years. Despite the thousands of papers that have been(More)
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