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Abstract：
Coastal systems worldwide deliver vital ecosystem services, such as biodiversity, carbon sequestration, and coastal protection. Effectivity of these ecosystem services increases when vegetation is present. Understanding the mechanisms behind vegetation establishment in bio-geomorphic systems is necessary to understand their ability to recover after erosive events and potential adaptations to climate change. In this study, we examined how seed availability affects vegetation establishment in the salt marsh-intertidal flat transition zone: the area with capacity for lateral marsh expansion. This requires vegetation establishment; therefore, seed availability is essential. In a 6-month field experiment, we simulated a before and after winter seed dispersal at two locations, the salt-marsh vegetation edge and the intertidal flat, and studied seed retention, the seed bank, and the seed viability of three pioneer marsh species: Salicornia procumbens, Aster tripolium, and Spartina anglica. During winter storm conditions, all supplied seeds eroded away with the sediment surface layer. After winter, supplied seeds from all three species were retained, mostly at the surface while 9% was bioturbated downwards. In the natural seed bank, A. tripolium and S. anglica were practically absent while S. procumbens occurred more frequently. The viability of S. procumbens seeds was highest at the surface, between 80% and 90%. The viability quickly decreased with depth, although viable S. procumbens seeds occurred up to 15 cm depth. Only when seeds were supplied after winter, many S. procumbens and some S. anglica individuals did establish successfully in the transition zone. Viable seed availability formed a vegetation establishment threshold, even with a local seed source. Our results suggest that, although boundary conditions such as elevation, inundation, and weather conditions were appropriate for vegetation establishment in spring, the soil surface in winter can be so dynamic that it limits lateral marsh expansion. These insights can be used for designing effective nature-based coastal protection.
摘要：
全球沿海系统提供重要的生态系统服务，比如生物多样性，碳封存，和海岸保护。当存在植被时，这些生态系统服务的有效性会增加。了解生物地貌系统中植被建立背后的机制对于了解其在侵蚀事件和对气候变化的潜在适应后恢复的能力是必要的。在这项研究中,我们研究了种子的可用性如何影响盐沼-潮间带过渡带的植被建立：具有横向沼泽扩展能力的区域。这需要建立植被；因此，种子的可用性至关重要。在为期6个月的野外实验中,我们在两个地点模拟了冬季种子扩散前后，盐沼植被边缘和潮间带，并研究了种子的保留，种子银行,和三种先锋沼泽物种的种子活力：海蓬草，AsterTripolium,还有SpartinaAnglica.在冬季风暴条件下，所有供应的种子都被沉积物表层侵蚀掉了。冬天过后,从所有三个物种提供的种子被保留，主要在地表，而9%的生物扰动向下。在自然种子库中，A.tripolium和S.anglica几乎不存在，而S.procumbens发生的频率更高。S.procumbens种子的生存力在表面最高，在80%到90%之间。生存能力随深度迅速下降，尽管可行的S.procumbens种子的深度可达15厘米。只有当种子在冬季后供应时，许多S.procumbens和一些圣利卡人确实在过渡区成功建立了。可行的种子可用性形成了植被建立阈值，即使有当地的种子来源。我们的研究结果表明,虽然边界条件如高程，淹没,天气条件适合春季植被的建立，冬季的土壤表面可能非常动态，以至于限制了沼泽的横向扩展。这些见解可用于设计有效的基于自然的沿海保护。
