The Unique Ability of Fine Roots to Reduce Vegetated Coastal Dune Erosion During Wave Collision
The Unique Ability of Fine Roots to Reduce Vegetated Coastal Dune Erosion During Wave Collision
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DOI：
10.3389/fbuil.2022.904837
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发表时间：
2022-07-12
影响因子：
3
通讯作者：
Armitage, Anna R.
中科院分区：
文献类型：
--
作者：
Figlus, Jens;Sigren, Jacob M.;Armitage, Anna R.
沿海植被沙丘在风暴潮和海浪袭击期间可以作为侵蚀缓冲，因此可以成为减少洪水风险计划的重要组成部分。然而，植物形态对波浪侵蚀过程的影响很难量化，部分原因是水动力、形态动力和生物过程耦合的复杂性。本文通过波浪水槽试验，研究了波浪作用下4种植被类型对沙丘侵蚀过程的影响。包含不同生长阶段的真实植物排列的沙丘剖面暴露在水位的不规则波浪中，产生碰撞状态以模拟风暴影响。采用逐步多元统计分析方法确定地上、地下植物变量与物理响应的关系。植物变量包括细根生物量、粗根生物量、地上表面积、茎旋转刚度和菌根定植。其中，形态变量包括侵蚀沉积物体积、跨岸区域质心移动和陡崖退缩率。结果表明，在碰撞过程中，植被能够减少高达37%的侵蚀。虽然发现这种减少与地上和地下植物结构及其对水动力过程的影响有关，但主要是由于细根生物量的存在。细根增加了沉积物的抗剪强度，从而降低了侵蚀体积和陡坡退缩速率。每增加100 mg/L细根（干根），侵蚀体积减少6.6%，陡坡退缩速率减缓4.6%。粗根和植物介导的菌根定植没有显著改变这些结果，细根也没有引起波反射的明显增强。总之，细根提供了一种独特的结合沉积物的能力，从而减少了沙丘的侵蚀。
Vegetated coastal sand dunes can be vital components of flood risk reduction schemes due to their ability to act as an erosive buffer during storm surge and wave attack. However, the effects of plant morphotypes on the wave-induced erosion process are hard to quantify, in part due to the complexity of the coupled hydrodynamic, morphodynamic, and biological processes involved. In this study the effects of four vegetation types on the dune erosion process under wave action was investigated in a wave flume experiment. Sand dune profiles containing real plant arrangements at different growth stages were exposed to irregular waves at water levels producing a collision regime to simulate storm impact. Stepwise multivariate statistical analysis was carried out to determine the relationship of above- and below-ground plant variables to the physical response. Plant variables included, among others, fine root biomass, coarse root biomass, above-ground surface area, stem rotational stiffness, and mycorrhizal colonization. Morphologic variables, among others, included eroded sediment volume, cross-shore area centroid shift, and scarp retreat rate. Results showed that vegetation was able to reduce erosion during a collision regime by up to 37%. Although this reduction was found to be related to both above- and belowground plant structures and their effect on hydrodynamic processes, it was primarily accounted for by the presence of fine root biomass. Fine roots increased the shear strength of the sediment and thus lowered erosional volumes and scarp retreat rates. For each additional 100 mg/L of fine roots (dry) added to the sediment, the erosional volume was reduced by 6.6% and the scarp retreat rate was slowed by 4.6%. Coarse roots and plant-mediated mycorrhizal colonization did not significantly alter these outcomes, nor did the apparent enhancement of wave reflection caused by the fine roots. In summary, fine roots provided a unique ability to bind sediment leading to reduced dune erosion.