Laboratory of Plant Ecology, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, B-9000, Ghent, Belgium.
Daniel B. Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA, 30602, USA.
New Phytol. 2012 Oct;196(2):448-461. doi: 10.1111/j.1469-8137.2012.04267.x. Epub 2012 Aug 16.
Here, we investigated the effect of different heat-wave intensities applied at two atmospheric CO2 concentrations ([CO2]) on seedlings of two tree species, loblolly pine (Pinus taeda) and northern red oak (Quercus rubra). Seedlings were assigned to treatment combinations of two levels of [CO2] (380 or 700 μmol mol(-1)) and four levels of air temperature (ambient, ambient +3°C, or 7-d heat waves consisting of a biweekly +6°C heat wave, or a monthly +12°C heat wave). Treatments were maintained throughout the growing season, thus receiving equal heat sums. We measured gas exchange and fluorescence parameters before, during and after a mid-summer heat wave. The +12°C heat wave, significantly reduced net photosynthesis (Anet) in both species and [CO2] treatments but this effect was diminished in elevated [CO2]. The decrease in Anet was accompanied by a decrease in Fv'/Fm' in P. taeda and ΦPSII in Q. rubra. Our findings suggest that, if soil moisture is adequate, trees will experience negative effects in photosynthetic performance only with the occurrence of extreme heat waves. As elevated [CO2] diminished these negative effects, the future climate may not be as detrimental to plant communities as previously assumed.
在这里，我们研究了在两种大气 CO2 浓度 ([CO2]) 下应用不同热强度对两种树种的幼苗的影响，火炬松（Pinus taeda）和北方红栎（Quercus rubra）。幼苗被分配到两种 [CO2] 水平（380 或 700 μmol mol(-1)) 和四种空气温度水平（环境温度、环境温度+3°C 或 7 天的热波，包括每周两次的+6°C 热波或每月一次的+12°C 热波）的处理组合中。在整个生长季节，处理都保持不变，因此接收相等的热量总和。我们在中夏热波之前、期间和之后测量了气体交换和荧光参数。+12°C 的热波显著降低了两种物种和 [CO2] 处理的净光合速率（Anet），但在高浓度 [CO2] 下，这种效应减弱。Anet 的降低伴随着 P. taeda 的 Fv'/Fm'和 Q. rubra 的 ΦPSII 的降低。我们的研究结果表明，如果土壤水分充足，树木只有在发生极端热波时才会经历光合作用性能的负面效应。由于高浓度 [CO2] 减轻了这些负面影响，未来的气候可能不会像以前假设的那样对植物群落产生不利影响。
