Department of Biology, University of Eastern Finland, PO Box 111, FI-80101 Joensuu, Finland.
Tree Physiol. 2011 Aug;31(8):808-18. doi: 10.1093/treephys/tpr075. Epub 2011 Aug 18.
Rising temperature and tropospheric ozone (O(3)) concentrations are likely to affect carbon assimilation processes and thus the carbon sink strength of trees. In this study, we investigated the joint action of elevated ozone and temperature on silver birch (Betula pendula) and European aspen (Populus tremula) saplings in field conditions by combining free-air ozone exposure (1.2 × ambient) and infrared heaters (ambient +1.2 °C). At leaf level measurements, elevated ozone decreased leaf net photosynthesis (P(n)), while the response to elevated temperature was dependent on leaf position within the foliage. This indicates that leaf position has to be taken into account when leaf level data are collected and applied. The ozone effect on P(n) was partly compensated for at elevated temperature, showing an interactive effect of the treatments. In addition, the ratio of photosynthesis to stomatal conductance (P(n)/g(s) ratio) was decreased by ozone, which suggests decreasing water use efficiency. At the plant level, the increasing leaf area at elevated temperature resulted in a considerable increase in photosynthesis and growth in both species.
气温升高和对流层臭氧（O(3)）浓度升高可能会影响碳同化过程，从而影响树木的碳汇强度。在这项研究中，我们通过结合自由空气臭氧暴露（1.2×环境浓度）和红外加热器（环境温度+1.2°C），在野外条件下研究了臭氧和温度升高对银桦（Betula pendula）和欧洲山杨（Populus tremula）幼树的联合作用。在叶片水平的测量中，臭氧升高降低了叶片净光合速率（P(n)），而对高温的响应取决于叶片在树冠中的位置。这表明在收集和应用叶片水平数据时，必须考虑叶片位置。臭氧对 P(n)的影响在高温下部分得到了补偿，表明处理之间存在交互作用。此外，臭氧降低了光合作用与气孔导度的比值（P(n)/g(s) 比值），这表明水分利用效率降低。在植株水平上，高温下叶片面积的增加导致两种物种的光合作用和生长都有显著增加。
