Abstract
Rising atmospheric carbon dioxide (CO
2) may alleviate the toxicological impacts of concurrently rising tropospheric ozone (O
3) during the present century if higher CO
2 is accompanied by lower stomatal conductance (g
s), as assumed by many models. We investigated how elevated concentrations of CO
2 and O
3, alone and in combination, affected the accumulated stomatal flux of O
3 (AFst) by canopies and sun leaves in closed aspen and aspen-birch forests in the free-air CO
2-O
3 enrichment experiment near Rhinelander, Wisconsin. Stomatal conductance for O
3 was derived from sap flux data and AFst was estimated either neglecting or accounting for the potential influence of non-stomatal leaf surface O
3 deposition. Leaf-level AFst (AFstl) was not reduced by elevated CO
2. Instead, there was a significant CO
2 x O
3 interaction on AFst
l, as a consequence of lower values of g
s in control plots and the combination treatment than in the two single-gas treatments. In addition, aspen leaves had higher AFst
l than birch leaves, and estimates of AFst
l were not very sensitive to non-stomatal leaf surface O
3 deposition. Our results suggest that model projections of large CO
2-induced reductions in g
s alleviating the adverse effect of rising tropospheric O
3 may not be reasonable for northern hardwood forests.
Keywords
carbon dioxide,
FACE,
forest,
ozone flux,
stomata
Citation
Uddling, Johan; Hogg, Alan J.; Teclaw, Ronald M.; Carroll, Mary Anne.; Ellsworth, David S. 2010. Stomatal uptake of O
3 in aspen and aspen-birch forests under free-air CO
2 and O
3 enrichment. Environmental Pollution. 158(4): 2023-2031.