Gauthey Alice, Backes Diana, Balland Jeff, Alam Iftakharul, Maher Damien T, Cernusak Lucas A, Duke Norman C, Medlyn Belinda E, Tissue David T, Choat Brendan
Hawkesbury Institute for the Environment, Western Sydney University, Richmond, NSW, Australia.
Plant Ecology Research Laboratory PERL, Ecole Polytechnique Fédérale de Lausanne EPFL, Lausanne, Switzerland.
Front Plant Sci. 2022 Apr 27;13:822136. doi: 10.3389/fpls.2022.822136. eCollection 2022.
Between late 2015 and early 2016, more than 7,000 ha of mangrove forest died along the coastline of the Gulf of Carpentaria, in northern Australia. This massive die-off was preceded by a strong 2015/2016 El Niño event, resulting in lower precipitation, a drop in sea level and higher than average temperatures in northern Australia. In this study, we investigated the role of hydraulic failure in the mortality and recovery of the dominant species, , 2 years after the mortality event. We measured predawn water potential (Ψ) and percent loss of stem hydraulic conductivity (PLC) in surviving individuals across a gradient of impact. We also assessed the vulnerability to drought-induced embolism (Ψ) for the species. Areas with severe canopy dieback had higher native PLC (39%) than minimally impacted areas (6%), suggesting that hydraulic recovery was ongoing. The high resistance of to water-stress-induced embolism (Ψ = -9.6 MPa), indicates that severe water stress (Ψ < -10 MPa) would have been required to cause mortality in this species. Our data indicate that the natural gradient of water-stress enhanced the impact of El Niño, leading to hydraulic failure and mortality in growing on severely impacted (SI) zones. It is likely that lowered sea levels and less frequent inundation by seawater, combined with lower inputs of fresh water, high evaporative demand and high temperatures, led to the development of hyper-salinity and extreme water stress during the 2015/16 summer.
2015年末至2016年初，澳大利亚北部卡奔塔利亚湾沿岸7000多公顷的红树林死亡。在这次大规模死亡事件之前，2015/2016年发生了强烈的厄尔尼诺事件，导致澳大利亚北部降水量减少、海平面下降以及气温高于平均水平。在本研究中，我们调查了死亡事件发生2年后，水力衰竭在优势物种死亡率和恢复过程中的作用。我们在不同影响梯度下测量了存活个体的黎明前水势（Ψ）和茎干水力导度损失百分比（PLC）。我们还评估了该物种对干旱诱导栓塞（Ψ）的脆弱性。树冠严重枯死的区域原生PLC（39%）高于受影响最小的区域（6%），这表明水力恢复正在进行。该物种对水分胁迫诱导栓塞具有高抗性（Ψ = -9.6 MPa），这表明该物种需要严重的水分胁迫（Ψ < -10 MPa）才会导致死亡。我们的数据表明，水分胁迫的自然梯度增强了厄尔尼诺的影响，导致生长在严重受影响（SI）区域的该物种发生水力衰竭和死亡。很可能是海平面下降、海水淹没频率降低，加上淡水输入减少、蒸发需求高和气温高，导致2015/16年夏季出现高盐度和极端水分胁迫。
