Department of Forest Resources, University of Minnesota, 1530 Cleveland Avenue N, St. Paul, MN, 55108, USA.
Glob Chang Biol. 2015 Mar;21(3):1342-57. doi: 10.1111/gcb.12781. Epub 2014 Dec 23.
Rising temperatures caused by climate change could negatively alter plant ecosystems if temperatures exceed optimal temperatures for carbon gain. Such changes may threaten temperature-sensitive species, causing local extinctions and range migrations. This study examined the optimal temperature of net photosynthesis (Topt ) of two boreal and four temperate deciduous tree species grown in the field in northern Minnesota, United States under two contrasting temperature regimes. We hypothesized that Topt would be higher in temperate than co-occurring boreal species, with temperate species exhibiting greater plasticity in Topt , resulting in better acclimation to elevated temperatures. The chamberless experiment, located at two sites in both open and understory conditions, continuously warmed plants and soils during three growing seasons. Results show a modest, but significant shift in Topt of 1.1 ± 0.21 °C on average for plants subjected to a mean 2.9 ± 0.01 °C warming during midday hours in summer, and shifts with warming were unrelated to species native ranges. The 1.1 °C shift in Topt with 2.9 °C warming might be interpreted as suggesting limited capacity to shift temperature response functions to better match changes in temperature. However, Topt of warmed plants was as well-matched with prior midday temperatures as Topt of plants in the ambient treatment, and Topt in both treatments was at a level where realized photosynthesis was within 90-95% of maximum. These results suggest that seedlings of all species were close to optimizing photosynthetic temperature responses, and equally so in both temperature treatments. Our study suggests that temperate and boreal species have considerable capacity to match their photosynthetic temperature response functions to prevailing growing season temperatures that occur today and to those that will likely occur in the coming decades under climate change.
气候变化导致的气温升高，如果超过了碳增益的最佳温度，可能会对植物生态系统产生负面影响。这种变化可能会威胁到对温度敏感的物种，导致它们在当地灭绝和迁徙。本研究在美国明尼苏达州北部的野外条件下，在两个对比的温度条件下，研究了两种北方树种和四种温带落叶树种的净光合速率（Topt）的最佳温度。我们假设温带树种的 Topt 会比同时存在的北方树种高，并且温带树种的 Topt 具有更大的可塑性，从而更好地适应高温。该无腔室实验位于两个地点，分别在开阔地和林下条件下进行，在三个生长季节中连续对植物和土壤进行加热。结果表明，在夏季中午，植物平均接受 2.9°C±0.01°C 的平均增温，Topt 平均有 1.1°C±0.21°C 的适度但显著的变化，并且与物种的原生范围无关。Topt 在 2.9°C 的增温下变化 1.1°C，可能表明其向更好地适应温度变化的温度响应函数转变的能力有限。然而，与对照处理相比，增温植物的 Topt 与之前的中午温度相匹配，并且两种处理中的 Topt 都达到了实际光合作用在 90-95%最大光合作用的水平。这些结果表明，所有树种的幼苗都接近优化光合温度响应，并且在两种温度处理中都一样。我们的研究表明，温带和北方树种具有相当大的能力，使其光合温度响应功能与当今出现的、以及在未来几十年内气候变化下可能出现的盛行生长季节温度相匹配。
