External conditions drive optimal planting configurations for salt marsh restoration
External conditions drive optimal planting configurations for salt marsh restoration
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DOI：
10.1111/1365-2664.13550
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发表时间：
2020-03
影响因子：
5.7
通讯作者：
Mollie F. Duggan‐Edwards;J. Pagès;S. Jenkins;T. Bouma;M. Skov
中科院分区：
文献类型：
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作者：
Mollie F. Duggan‐Edwards;J. Pagès;S. Jenkins;T. Bouma;M. Skov
1. 沿海盐沼受到风暴侵蚀和海平面上升的威胁，导致防洪、野生动物和娱乐空间的损失。尽管已经花费了超过10亿美元来弥补损失，但由于种植斑块在具有挑战性的波浪和当前条件下生存能力差，恢复工作取得了不同程度的成功。定植或重新种植后的沼泽扩张受植被密度和沉积物捕获之间的正负反馈调节。茂密的植被促进了沉积物的捕获和垂直斑块的生长，但通过将水文能量集中到斑块边缘的侵蚀沟渠中，对斑块的扩展产生了负面限制。相反，低密度植被可能无法模拟足够的沉积物捕获，这增加了植物迁移死亡率。正反馈和负反馈的强度会随着波浪的暴露而变化，但这从未在自然条件下进行过测试。我们观察了在3个植被密度水平、3个波浪强迫水平（3个站点）上种植的小孢子草斑块（0.8 × 0.8 m）的密度依赖性沉积物反馈、存活和侧向扩张。3. 我们发现植物密度和强迫对正反馈和负反馈的强度有交互作用。密度相关的反馈只出现在中等和暴露的条件下：典型的沼泽丛斑形状，由于正（垂直生长）和负（沟壑）反馈的结合而产生，只与暴露条件下的高密度植被有关。在高暴露的情况下，密集的种植可以转移植被的能量，从而提高存活率。在遮荫条件下，中等密度的扩张最大，而密集斑块的死亡率和侵蚀率较高。合成与应用。湿地恢复的成功显然取决于考虑环境压力和种植密度之间的相互作用。在具有挑战性的高暴露环境中，大面积的密集种植将最大限度地提高成功率，因为植物促进了沉积物的捕获，而负面边缘效应（沟槽）将减少大面积斑块的比例。然而，随着环境压力的减少，密集种植的好处将从积极（促进）转变为消极（竞争），此时中等密度的种植可能是最佳的。在整个生态系统中，沿着压力梯度在正反馈和负反馈之间切换是很常见的。我们呼吁在修复设计中更广泛地整合促进和应力梯度原则，以确保修复成功。
1. Coastal salt marshes are threatened by erosion from storminess and sea level rise, with resulting losses in flood protection, wildlife and recreational space. Although more than $1 billion has been spent to reconcile losses, restoration has had varying success because of poor survival of planted patches in challenging wave and current conditions. Marsh expansion after colonization or replanting is regulated by positive and negative feedbacks between vegetation density and sediment capture. Dense vegetation stimulates sediment capture and vertical patch growth, but negatively constrains patch expansion by concentrating hydrological energy into erosion gullies along patch edges. Conversely, low‐density vegetation may not simulate enough sediment capture, which increases plant dislodgement mortality. The strengths of positive and negative feedbacks will vary with wave exposure, but this has never been tested in natural conditions.2. We observed density‐dependent sediment feedbacks, survival and lateral expansion by Sporobolus anglicus patches (0.8 × 0.8 m) planted at three levels of vegetation density, at each of three levels of wave forcing (three sites). 3. We found interactive effects of plant density and forcing on the strength of positive and negative feedbacks. Density‐dependent feedbacks only emerged in moderate and exposed conditions: classic marsh tussock patch shapes, which arise due to combined positive (vertical growth) and negative (gullies) feedbacks, were only associated with high density vegetation under exposed conditions. At high exposure, survival was enhanced by dense planting, which diverted energy away from the vegetation. In sheltered conditions, expansion was the greatest at medium density, while dense patches had high mortality and erosion.4. Synthesis and applications. Success of wetland restoration clearly hinges on considering interactions between environmental stress and planting density. In challenging high‐exposure settings, dense planting in large patches should maximize success, as plant facilitation boosts sediment capture and negative edge effects (gullies) will represent a diminished proportion of larger patches. Yet, benefits of dense planting will switch from positive (facilitation) to negative (competition) with reduced environmental stress, when moderate‐density planting might be optimal. Switches along stress gradients between positive and negative feedbacks are common across ecosystems. We call for wider integration of facilitation and stress–gradient principles into restoration design to safeguard restoration successes.