Climate change is projected to increase the frequency of extreme drought events, which can have dramatic consequences for ecosystems. Extreme drought may interact with other stressors such as invasion by non‐native species, yet little research has explored these dynamics. Here, we examine the physical mechanisms and temporal scale underlying a dieback of an invasive non‐native plant, Lepidium latifolium, in tidal salt marshes of the San Francisco Bay, California, USA, during an extreme, multi‐year drought occurring from 2012 to 2015. Using generalized additive mixed models (GAMMs), we explored the relationship between eight years of estuarine salinity data and five years of L. latifolium density data from three marshes spanning a gradient of salinity across the San Francisco Bay. We found a significant time‐lagged (3 yr) effect of estuarine salinity on L. latifolium density, with high salinities preceding reductions in L. latifolium densities and low salinities preceding increases. The most dramatic change in stem density, a 54% reduction in 2015, was preceded by a salinity increase of 43% from 2011 to 2012. We found the L. latifolium decline was driven by impacts on mature, rather than young, plants. Additionally, we tested the importance of local precipitation in driving L. latifolium densities in a one‐season rain exclusion experiment. We found 100% exclusion of precipitation during one rainy season (January–mid‐May) did not have a significant impact on densities of mature stands of L. latifolium. Our finding that estuarine salinity was a key driver of L. latifolium invasion dynamics suggests sea level rise, like extreme drought, may hinder L. latifolium invasion, as it will also raise estuarine salinities. Further, our study highlights the importance of temporal lags in understanding climate change impacts on biological invasions, which has received very little study to date.

中文翻译：

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多年干旱对潮汐盐沼植物入侵的时滞影响

预计气候变化将增加极端干旱事件的发生频率，这可能对生态系统产生重大影响。极端干旱可能与其他压力源相互作用，例如非本地物种的入侵，但很少有研究探讨这些动态。在这里，我们研究了2012年至2012年极端多年干旱期间，美国加利福尼亚旧金山湾潮汐盐沼中的一种入侵性非本土植物Lepidium latifolium死亡的物理机制和时间尺度。2015年。使用广义加性混合模型（GAMMs），我们探讨了八年河口盐度数据与五年紫花苜蓿之间的关系。来自三个沼泽的密度数据，跨越整个旧金山湾的盐度梯度。我们发现了一个显著时间滞后（3年）河口盐度对效果L.宽叶密度，具有高盐度前述在减少L.宽叶密度和前述增加低盐度。茎密度变化最为剧烈，2015年下降了54％，而从2011年到2012年，盐度却增加了43％。我们发现，L。latifolium下降的原因是对成熟植物的影响，而不是对年轻植物的影响。此外，我们测试了本地降水在驱动L. latifolium中的重要性一季降雨排除实验中的密度。我们发现在一个雨季（1月至5月中旬）100％的降水量排除对L. latifolium成熟林分的密度没有显着影响。我们的研究结果表明，河口盐度是L. latifolium入侵动力学的主要驱动力，这表明海平面上升（如极端干旱）可能会阻止L. latifolium的入侵，因为这也会提高河口盐度。此外，我们的研究强调了时间滞后对于理解气候变化对生物入侵的影响的重要性，迄今为止，该研究还很少。