Stagg Camille LaFosse, Osland Michael J, Moon Jena A, Feher Laura C, Laurenzano Claudia, Lane Tiffany C, Jones William R, Hartley Stephen B
U.S. Geological Survey, Wetland and Aquatic Research Center, Lafayette, LA 70506, USA.
U.S. Fish and Wildlife Service, Unified Regions 6&7, Upper Gulf Coast Zone, Winnie, TX 77665, USA.
Plants (Basel). 2021 Sep 5;10(9):1841. doi: 10.3390/plants10091841.
Climate extremes are becoming more frequent with global climate change and have the potential to cause major ecological regime shifts. Along the northern Gulf of Mexico, a coastal wetland in Texas suffered sudden vegetation dieback following an extreme precipitation and flooding event associated with Hurricane Harvey in 2017. Historical salt marsh dieback events have been linked to climate extremes, such as extreme drought. However, to our knowledge, this is the first example of extreme precipitation and flooding leading to mass mortality of the salt marsh foundation species, . Here, we investigated the relationships between baseline climate conditions, extreme climate conditions, and large-scale plant mortality to provide an indicator of ecosystem vulnerability to extreme precipitation events. We identified plant zonal boundaries along an elevation gradient with plant species tolerant of hypersaline conditions, including succulents and graminoids, at higher elevations, and flood-tolerant species, including , at lower elevations. We quantified a flooding threshold for wetland collapse under baseline conditions characterized by incremental increases in flooding (i.e., sea level rise). We proposed that the sudden widespread dieback of following Hurricane Harvey was the result of extreme precipitation and flooding that exceeded this threshold for survival. Indeed, dieback occurred at elevations above the wetland collapse threshold, illustrating a heightened vulnerability to flooding that could not be predicted from baseline climate conditions. Moreover, the spatial pattern of vegetation dieback indicated that underlying stressors may have also increased susceptibility to dieback in some marshes.Collectively, our results highlight a new mechanism of sudden vegetation dieback in marshes that is triggered by extreme precipitation and flooding. Furthermore, this work emphasizes the importance of considering interactions between multiple abiotic and biotic stressors that can lead to shifts in tolerance thresholds and incorporating climate extremes into climate vulnerability assessments to accurately characterize future climate threats.
随着全球气候变化，极端气候事件愈发频繁，有可能导致重大生态系统状态转变。在墨西哥湾北部，得克萨斯州的一处沿海湿地在2017年与飓风哈维相关的极端降水和洪水事件后，植被突然死亡。历史上盐沼植被死亡事件与极端气候有关，比如极端干旱。然而，据我们所知，这是极端降水和洪水导致盐沼基础物种大量死亡的首个实例。在此，我们研究了基线气候条件、极端气候条件与大规模植物死亡之间的关系，以提供生态系统对极端降水事件脆弱性的指标。我们沿着海拔梯度确定了植物带边界，在较高海拔处有耐高盐条件的植物物种，包括多肉植物和禾本科植物，在较低海拔处有耐洪物种，包括[具体物种缺失]。我们量化了在以洪水逐渐增加（即海平面上升）为特征的基线条件下湿地崩溃的洪水阈值。我们提出，飓风哈维过后[具体植物缺失]突然大面积死亡是极端降水和洪水超过了该[具体植物缺失]生存阈值的结果。事实上，[具体植物缺失]死亡发生在湿地崩溃阈值以上的海拔高度，说明对洪水的脆弱性增加，而这无法从基线气候条件预测。此外，植被死亡的空间格局表明，潜在压力源可能也增加了一些[具体盐沼缺失]盐沼对死亡的易感性。总体而言，我们的结果突出了盐沼植被因极端降水和洪水引发突然死亡的新机制。此外，这项工作强调了考虑多种非生物和生物压力源之间相互作用的重要性，这些相互作用会导致耐受阈值的变化，并将极端气候纳入气候脆弱性评估，以准确描述未来气候威胁。
