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High heat tolerance, evaporative cooling, and stomatal decoupling regulate canopy temperature and their safety margins in three European oak species
Global Change Biology ( IF 10.8 ) Pub Date : 2024-08-02 , DOI: 10.1111/gcb.17439 Alice Gauthey 1, 2, 3 , Ansgar Kahmen 4 , Jean-Marc Limousin 5 , Alberto Vilagrosa 6 , Margaux Didion-Gency 7 , Eugénie Mas 1, 2, 8 , Arianna Milano 1, 2 , Alex Tunas 1, 2, 9 , Charlotte Grossiord 1, 2
Global Change Biology ( IF 10.8 ) Pub Date : 2024-08-02 , DOI: 10.1111/gcb.17439 Alice Gauthey 1, 2, 3 , Ansgar Kahmen 4 , Jean-Marc Limousin 5 , Alberto Vilagrosa 6 , Margaux Didion-Gency 7 , Eugénie Mas 1, 2, 8 , Arianna Milano 1, 2 , Alex Tunas 1, 2, 9 , Charlotte Grossiord 1, 2
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Heatwaves and soil droughts are increasing in frequency and intensity, leading many tree species to exceed their thermal thresholds, and driving wide‐scale forest mortality. Therefore, investigating heat tolerance and canopy temperature regulation mechanisms is essential to understanding and predicting tree vulnerability to hot droughts. We measured the diurnal and seasonal variation in leaf water potential (Ψ), gas exchange (photosynthesis A net and stomatal conductance g s ), canopy temperature (T can ), and heat tolerance (leaf critical temperature T crit and thermal safety margins TSM, i.e., the difference between maximum T can and T crit ) in three oak species in forests along a latitudinal gradient (Quercus petraea in Switzerland, Quercus ilex in France, and Quercus coccifera in Spain) throughout the growing season. Gas exchange and Ψ of all species were strongly reduced by increased air temperature (T air ) and soil drying, resulting in stomatal closure and inhibition of photosynthesis in Q. ilex and Q. coccifera when T air surpassed 30°C and soil moisture dropped below 14%. Across all seasons, T can was mainly above T air but increased strongly (up to 10°C > T air ) when A net was null or negative. Although trees endured extreme T air (up to 42°C), positive TSM were maintained during the growing season due to high T crit in all species (average T crit of 54.7°C) and possibly stomatal decoupling (i.e., A net ≤0 while g s >0). Indeed, Q. ilex and Q. coccifera trees maintained low but positive g s (despite null A net ), decreasing Ψ passed embolism thresholds. This may have prevented T can from rising above T crit during extreme heat. Overall, our work highlighted that the mechanisms behind heat tolerance and leaf temperature regulation in oak trees include a combination of high evaporative cooling, large heat tolerance limits, and stomatal decoupling. These processes must be considered to accurately predict plant damages, survival, and mortality during extreme heatwaves.
中文翻译：
高耐热性、蒸发冷却和气孔解耦调节三种欧洲橡树树种的冠层温度及其安全裕度
热浪和土壤干旱的频率和强度不断增加，导致许多树种超过其热阈值，并导致大范围的森林死亡。因此，研究耐热性和冠层温度调节机制对于了解和预测树木对热干旱的脆弱性至关重要。我们测量了叶水势 (Ψ)、气体交换（光合作用）的日变化和季节变化一个网和气孔导度克s ）、冠层温度（时间能）和耐热性（叶临界温度时间暴击和热安全裕度 TSM，即最大之间的差值时间能和时间暴击）在森林中沿纬度梯度的三种橡树物种中（山栎在瑞士，冬青在法国，以及红栎在西班牙）整个生长季节。所有物种的气体交换和 Ψ 均因气温升高而大幅降低（时间空气）和土壤干燥，导致气孔关闭和光合作用抑制冬青和球栎什么时候时间空气气温超过30°C，土壤湿度降至14%以下。跨越四季，时间能主要是上面的时间空气但急剧增加（高达 10°C >时间空气） 什么时候一个网为空或负数。 尽管树木经历了极端的考验时间空气（高达 42°C），由于高温，在生长季节期间 TSM 保持正值时间暴击在所有物种中（平均时间暴击54.7°C）和可能的气孔脱钩（即，一个网≤0 同时克s >0)。的确，冬青和球花栎树木保持低矮但积极克s （尽管为空一个网），减少 Ψ 通过栓塞阈值。这可能阻止了时间能从上升到上面时间暴击在极热的情况下。总的来说，我们的工作强调了橡树耐热性和叶片温度调节背后的机制包括高蒸发冷却、大耐热极限和气孔解耦的组合。必须考虑这些过程才能准确预测极端热浪期间植物的损害、存活和死亡。
更新日期：2024-08-02
中文翻译：
高耐热性、蒸发冷却和气孔解耦调节三种欧洲橡树树种的冠层温度及其安全裕度
热浪和土壤干旱的频率和强度不断增加，导致许多树种超过其热阈值，并导致大范围的森林死亡。因此，研究耐热性和冠层温度调节机制对于了解和预测树木对热干旱的脆弱性至关重要。我们测量了叶水势 (Ψ)、气体交换（光合作用）的日变化和季节变化一个网和气孔导度克s ）、冠层温度（时间能）和耐热性（叶临界温度时间暴击和热安全裕度 TSM，即最大之间的差值时间能和时间暴击）在森林中沿纬度梯度的三种橡树物种中（山栎在瑞士，冬青在法国，以及红栎在西班牙）整个生长季节。所有物种的气体交换和 Ψ 均因气温升高而大幅降低（时间空气）和土壤干燥，导致气孔关闭和光合作用抑制冬青和球栎什么时候时间空气气温超过30°C，土壤湿度降至14%以下。跨越四季，时间能主要是上面的时间空气但急剧增加（高达 10°C >时间空气） 什么时候一个网为空或负数。 尽管树木经历了极端的考验时间空气（高达 42°C），由于高温，在生长季节期间 TSM 保持正值时间暴击在所有物种中（平均时间暴击54.7°C）和可能的气孔脱钩（即，一个网≤0 同时克s >0)。的确，冬青和球花栎树木保持低矮但积极克s （尽管为空一个网），减少 Ψ 通过栓塞阈值。这可能阻止了时间能从上升到上面时间暴击在极热的情况下。总的来说，我们的工作强调了橡树耐热性和叶片温度调节背后的机制包括高蒸发冷却、大耐热极限和气孔解耦的组合。必须考虑这些过程才能准确预测极端热浪期间植物的损害、存活和死亡。
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