Department of Plant and Environmental Sciences, University of Gothenburg, P.O. Box 461, SE-405 30 Göteborg, Sweden.
Environ Pollut. 2010 Jun;158(6):2023-31. doi: 10.1016/j.envpol.2009.12.001. Epub 2010 Jan 20.
Rising atmospheric carbon dioxide (CO2) may alleviate the toxicological impacts of concurrently rising tropospheric ozone (O3) during the present century if higher CO2 is accompanied by lower stomatal conductance (gs), as assumed by many models. We investigated how elevated concentrations of CO2 and O3, alone and in combination, affected the accumulated stomatal flux of O3 (AFst) by canopies and sun leaves in closed aspen and aspen-birch forests in the free-air CO2-O3 enrichment experiment near Rhinelander, Wisconsin. Stomatal conductance for O3 was derived from sap flux data and AFst was estimated either neglecting or accounting for the potential influence of non-stomatal leaf surface O3 deposition. Leaf-level AFst (AFst(l)) was not reduced by elevated CO2. Instead, there was a significant CO2 x O(3) interaction on AFst(l), as a consequence of lower values of gs 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 O3 deposition. Our results suggest that model projections of large CO2-induced reductions in gs alleviating the adverse effect of rising tropospheric O3 may not be reasonable for northern hardwood forests.
大气中二氧化碳（CO2）浓度的升高，如果伴随着气孔导度（gs）的降低，正如许多模型所假设的那样，可能会减轻本世纪同时上升的对流层臭氧（O3）的毒理学影响。我们在威斯康星州 Rhinelander 附近的自由空气 CO2-O3 增富实验中，研究了单独和联合升高的 CO2 和 O3 浓度如何影响封闭的山杨和山杨-桦木林冠层和阳叶的 O3 积累气孔通量（AFst）。通过 sap 通量数据得出 O3 的气孔导度，并且要么忽略、要么考虑非气孔叶面 O3 沉积的潜在影响来估计 AFst。升高的 CO2 并没有降低 O3 的气孔导度。相反，在对照和组合处理下，gs 值低于两种单气处理，导致 CO2 x O(3) 相互作用对 AFst(l) 产生影响。此外，山杨叶片的 AFst(l) 高于桦木叶片，并且非气孔叶面 O3 沉积对 AFst(l) 的估计值不太敏感。我们的结果表明，模型预测的 CO2 诱导的 gs 大量减少可能会缓解上升的对流层 O3 的不利影响，但对于北方硬木林来说可能并不合理。
