Importance of hydraulic strategy trade-offs in structuring response of canopy trees to extreme drought in central Amazon
Importance of hydraulic strategy trade-offs in structuring response of canopy trees to extreme drought in central Amazon
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DOI：
10.1007/s00442-021-04924-9
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发表时间：
2021-05-05
期刊：
影响因子：
2.7
通讯作者：
Oliveira, Rafael Silva
中科院分区：
文献类型：
--
作者：
Garcia, Maquelle Neves;Ferreira, Marciel Jose;Oliveira, Rafael Silva
植物在不同耐受逆境策略之间的生态生理权衡被广泛认为是塑造森林功能多样性和对气候变化的脆弱性的理论基础。然而，在自然干旱期间水力调节和气孔调节之间的权衡仍然没有得到充分的研究，特别是在热带森林。在2015年强烈的厄尔尼诺期间，我们调查了亚马逊中部的11棵成熟的林冠树木。我们发现，在亚马逊东部和中美洲降雨量较多的雨林中，木质部栓塞性(P-50=-3.3+/-0.8 Mpa)和水力安全裕度(HSM=2.12+/-0.57 Mpa)比以前观察到的更大。我们还发现，较高的树木表现出较低的栓塞性和较高的气孔敏感性，这是水力阻力和主动气孔调节之间的高度结构权衡。这种对树木水分状况的主动调节，由树干栓塞症的发生触发，作为一种反馈，以避免进一步增加栓塞症，也解释了光合作用和蒸腾作用的下降。这些结果表明，冠层树木表现出一种保守的耐旱水力策略，在投资木质部以减少水力失灵的脆弱性与积极的气孔调节以保护低水势之间进行权衡。这些发现提高了我们对热带森林树冠策略的理解，有助于更准确地预测干旱反应。
Plant ecophysiological trade-offs between different strategies for tolerating stresses are widely theorized to shape forest functional diversity and vulnerability to climate change. However, trade-offs between hydraulic and stomatal regulation during natural droughts remain under-studied, especially in tropical forests. We investigated eleven mature forest canopy trees in central Amazonia during the strong 2015 El Nino. We found greater xylem embolism resistance (P-50 = - 3.3 +/- 0.8 MPa) and hydraulic safety margin (HSM = 2.12 +/- 0.57 MPa) than previously observed in more precipitation-seasonal rainforests of eastern Amazonia and central America. We also discovered that taller trees exhibited lower embolism resistance and greater stomatal sensitivity, a height-structured trade-off between hydraulic resistance and active stomatal regulation. Such active regulation of tree water status, triggered by the onset of stem embolism, acted as a feedback to avoid further increases in embolism, and also explained declines in photosynthesis and transpiration. These results suggest that canopy trees exhibit a conservative hydraulic strategy to endure drought, with trade-offs between investment in xylem to reduce vulnerability to hydraulic failure, and active stomatal regulation to protect against low water potentials. These findings improve our understanding of strategies in tropical forest canopies and contribute to more accurate prediction of drought responses.