Elsey-Quirk Tracy, Lynn Austin, Jacobs Michael Derek, Diaz Rodrigo, Cronin James T, Wang Lixia, Huang Haosheng, Justic Dubravko
Department of Oceanography and Coastal Sciences, Louisiana State University, Baton Rouge, LA, USA.
College of Agriculture and Life Sciences, Cornell University, Ithaca, NY, 14850, USA.
Nat Commun. 2024 Apr 25;15(1):3518. doi: 10.1038/s41467-024-47828-x.
Vegetation dieback and recovery may be dependent on the interplay between infrequent acute disturbances and underlying chronic stresses. Coastal wetlands are vulnerable to the chronic stress of sea-level rise, which may affect their susceptibility to acute disturbance events. Here, we show that a large-scale vegetation dieback in the Mississippi River Delta was precipitated by salt-water incursion during an extreme drought in the summer of 2012 and was most severe in areas exposed to greater flooding. Using 16 years of data (2007-2022) from a coastwide network of monitoring stations, we show that the impacts of the dieback lasted five years and that recovery was only partial in areas exposed to greater inundation. Dieback marshes experienced an increase in percent time flooded from 43% in 2007 to 75% in 2022 and a decline in vegetation cover and species richness over the same period. Thus, while drought-induced high salinities and soil saturation triggered a significant dieback event, the chronic increase in inundation is causing a longer-term decline in cover, more widespread losses, and reduced capacity to recover from acute stressors. Overall, our findings point to the importance of mitigating the underlying stresses to foster resilience to both acute and persistent causes of vegetation loss.
植被枯死和恢复可能取决于罕见的急性干扰与潜在的慢性压力之间的相互作用。沿海湿地容易受到海平面上升的慢性压力影响，这可能会影响它们对急性干扰事件的易感性。在此，我们表明，2012年夏季极端干旱期间的盐水入侵引发了密西西比河三角洲的大规模植被枯死，且在遭受更大洪水的地区最为严重。利用来自沿海监测站网络的16年数据（2007 - 2022年），我们表明枯死的影响持续了五年，并且在遭受更大淹没的地区恢复只是部分恢复。枯死的沼泽地被洪水淹没的时间百分比从2007年的43%增加到2022年的75%，同时植被覆盖度和物种丰富度在同一时期有所下降。因此，虽然干旱导致的高盐度和土壤饱和引发了一次重大的枯死事件，但长期增加的淹没正在导致覆盖度的长期下降、更广泛的损失以及从急性压力源中恢复的能力降低。总体而言，我们的研究结果指出了减轻潜在压力以增强对植被损失的急性和持续性原因的恢复力的重要性。
