美国北亚利桑那大学Doughty, Christopher E.及其研究组人员提出了热带雨林正接近临界温度阈值的新见解。该研究于2023年8月23日发表于国际一流学术期刊《自然》杂志上。

研究揭示了从单个叶片温差电偶、地面辐射强度计和遥感(ECOSTRESS)独立三角测量的泛热带冠层温度，在干燥时期，中午峰值温度约为 34 °C，有一个长的高温尾部，可超过 40 °C。来自热带多个地点的叶片温差电偶数据表明，即使在中等温度的像素范围内，上部冠层叶片也有 0.01 %的时间超过 T_crit。此外，上层冠层叶片升温实验(巴西、波多黎各和澳大利亚分别为 +2，3 和 4 °C)非线性地提高了叶片温度，峰值叶片温度超过 T_crit 1.3 %的时间(超过 43.5 °C时为11%，超过 49.9 °C时为 0.3 %)。

研究使用包含这些动态的经验模型(经变暖实验数据验证)，研究人员发现，在代谢功能的潜在临界点之前，热带森林可以承受高达 3.9±0.5 °C的气温升高，但热带树木 T_crit 的可塑性和范围以及树叶死亡对树木死亡的影响的不确定性，可能会彻底改变这一预测。4.0 °C的估计值在热带森林气候变化预测的“最坏情况”(代表性浓度路径(RCP) 8.5)范围内，因此人们仍有能力决定(例如，通过不采用 RCP 6.0 或 8.5 路径)碳、水和生物多样性这些关键领域的命运。

据介绍，热带树木光合作用机制开始失效的临界温度平均约为 46.7 ℃(T_crit)。然而，仍然不清楚在气候变化的情况下，热带植被经历的叶子温度是否接近这个阈值或很快会达到这个阈值。

附：英文原文

Title: Tropical forests are approaching critical temperature thresholds

Author: Doughty, Christopher E., Keany, Jenna M., Wiebe, Benjamin C., Rey-Sanchez, Camilo, Carter, Kelsey R., Middleby, Kali B., Cheesman, Alexander W., Goulden, Michael L., da Rocha, Humberto R., Miller, Scott D., Malhi, Yadvinder, Fauset, Sophie, Gloor, Emanuel, Slot, Martijn, Oliveras Menor, Imma, Crous, Kristine Y., Goldsmith, Gregory R., Fisher, Joshua B.

Issue&Volume: 2023-08-23

Abstract: The critical temperature beyond which photosynthetic machinery in tropical trees begins to fail averages approximately 46.7°C (T_crit). However, it remains unclear whether leaf temperatures experienced by tropical vegetation approach this threshold or soon will under climate change. Here we found that pantropical canopy temperatures independently triangulated from individual leaf thermocouples, pyrgeometers and remote sensing (ECOSTRESS) have midday peak temperatures of approximately 34°C during dry periods, with a long high-temperature tail that can exceed 40°C. Leaf thermocouple data from multiple sites across the tropics suggest that even within pixels of moderate temperatures, upper canopy leaves exceed T_crit 0.01% of the time. Furthermore, upper canopy leaf warming experiments (+2, 3 and 4°C in Brazil, Puerto Rico and Australia, respectively) increased leaf temperatures non-linearly, with peak leaf temperatures exceeding T_crit 1.3% of the time (11% for more than 43.5°C, and 0.3% for more than 49.9°C). Using an empirical model incorporating these dynamics (validated with warming experiment data), we found that tropical forests can withstand up to a 3.9±0.5°C increase in air temperatures before a potential tipping point in metabolic function, but remaining uncertainty in the plasticity and range of T_crit in tropical trees and the effect of leaf death on tree death could drastically change this prediction. The 4.0°C estimate is within the ‘worst-case scenario’ (representative concentration pathway (RCP) 8.5) of climate change predictions for tropical forests and therefore it is still within our power to decide (for example, by not taking the RCP 6.0 or 8.5 route) the fate of these critical realms of carbon, water and biodiversity.

DOI: 10.1038/s41586-023-06391-z

Source: https://www.nature.com/articles/s41586-023-06391-z