Salt marshes play an important role in coastal protection by reducing the impact of waves and shoreline erosion risks. While mature vegetation is responsible for the persistence and stability of marsh ecosystems, seedling survival of pioneer species is especially crucial for marsh propagation. Marsh seedlings, however, may be threatened by climate change induced increased coastal storm surge intensity and accompanying (extreme) wave conditions, imposing stronger drag forces on marsh seedlings. We test the hypothesis that drag forces experienced by seedlings increase with horizontal orbital velocity (Uw) in a species-specific manner, and that the drag forces experienced are individual-plant trait-mediated. To test our hypotheses, seedlings of four contrasting pioneer marsh species (Bolboschoenus maritimus, Schoenoplectus tabernaemontani, Spartina anglica, and Puccinellia maritima) were exposed to storm wave conditions in a flume, where Uw and experienced drag forces were measured. Linear mixed effect models demonstrated that seedling’s susceptibility to storm wave conditions is at least partly mediated by individual plant traits. Drag forces experienced by seedlings tended to increase with Uw, and with stem length and diameter. The interplay of both traits was complex, with increasing stem length being the most important trait accounting for increases in drag forces experienced at low to moderate Uw, while the stem diameter became more important with increasing Uw. Furthermore, experienced drag forces appeared to be affected by species-specific traits such as rigidity and leaf growth, being highest for Bolboschoenus maritimus and lowest for Puccinellia maritima. Our results provide important mechanistic insights into the drivers of tidal marsh seedling vulnerability to storm wave conditions due to experienced drag, both based on the traits of individual plants and species-specific ones. This type of knowledge is of key importance when modelling saltmarsh establishment and resilience under climate change.

中文翻译：

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植物性状介导的拖曳力对四种潮汐沼泽先锋物种幼苗的影响

盐沼通过减少海浪的影响和海岸线侵蚀的风险，在海岸保护中发挥着重要作用。虽然成熟的植被负责沼泽生态系统的持久性和稳定性，但先锋物种的幼苗存活对于沼泽繁殖尤为重要。然而，沼泽幼苗可能受到气候变化的威胁，气候变化导致沿海风暴潮强度增加和伴随的（极端）波浪条件，对沼泽幼苗施加更大的阻力。我们检验了幼苗所经历的阻力随着水平轨道速度而增加的假设（üw）以特定于物种的方式，并且所经历的阻力是个体植物性状介导的。为了检验我们的假设，四种对比鲜明的先锋沼泽物种的幼苗（海豚,荸荠,当归， 和海锈菌) 暴露在水槽中的风暴波条件下，其中üw并测量了经验丰富的阻力。线性混合效应模型表明，幼苗对风暴波条件的敏感性至少部分由个体植物性状介导。幼苗所受的阻力随着üw, 以及茎的长度和直径。这两种性状的相互作用很复杂，增加的茎长是最重要的性状，可以解释低到中等阻力增加的原因üw，而茎直径随着增加而变得更加重要üw. 此外，经验丰富的阻力似乎受到物种特异性特征的影响，例如刚度和叶片生长，对于海豚最低的海锈菌. 我们的研究结果基于个体植物和特定物种的特征，为潮汐沼泽幼苗因经历过的阻力而易受风暴波条件影响的驱动因素提供了重要的机制见解。在模拟气候变化下的盐沼建立和复原力时，这类知识至关重要。