Intraspecific Root Trait Variability Along Environmental Gradients Affects Salt Marsh Resistance to Lateral Erosion
Intraspecific Root Trait Variability Along Environmental Gradients Affects Salt Marsh Resistance to Lateral Erosion
复制标题
DOI：
10.3389/fevo.2019.00150
复制
发表时间：
2019-05-08
影响因子：
3
通讯作者：
Griffin, John N.
中科院分区：
文献类型：
--
作者：
De Battisti, Davide;Fowler, Mike S.;Griffin, John N.
最近对盐沼的研究证明了植物根在稳定沉积物中的作用，从而证明了沼泽在提供海岸保护方面的重要性。然而，根特征和环境因素在控制沉积物稳定性方面的相对作用，以及根特征在沼泽内和沼泽之间的种内变异如何变化，仍然知之甚少。在这项研究中，我们调查了在海岸保护中具有重要作用的两个湿地物种(大米草和滨藜)的根特征(S)是如何驱动沉积物稳定性(抗侧向侵蚀)的，以及环境如何影响这些特征的表达。我们沿着盐度梯度在威尔士(英国)的两个河口各取样了三个沼泽，在每个物种各自的优势区建立了重复的样地。在所有样地中，我们采样了非生物变量(沙子、氧化还原电位、pH、盐度)和根特征(根密度、比根密度、根体积、根长密度)；在这些样地的一个子集(每个沼泽每种三个)中，我们提取了土壤-植物核心，并在水槽中评估了它们的抗侵蚀能力。根密度的增加和含沙量的减少提高了沉积物的稳定性。非生物变量对根密度的影响因物种不同而不同：在沙棘中，氧化还原是唯一显著的影响因素，对根密度有正的、线性的影响；在紫荆中，氧化还原对根密度有非线性的(U形)效应，而沙子对根密度有负的影响。综上所述，这些结果表明：(I)种内根系密度的变化可以影响盐沼沉积物的稳定性，(Ii)沉积物的性质不仅直接影响沉积物的稳定性，而且还通过根系密度间接影响沉积物的稳定性。这些结果揭示了盐沼对横向侵蚀稳定性的空间变异性，并建议将根密度纳入海岸植被监测计划，作为一种易于测量的根特征，将环境与沉积物稳定性联系起来，从而与沼泽提供的功能和服务相联系。
Recent studies in salt marshes have demonstrated the role of plant roots in sediment stabilisation, and hence the importance of marshes in providing coastal protection. However, the relative role of root traits and environmental factors in controlling sediment stability, and how intraspecific variability of root traits vary within and among marshes, remain poorly understood. In this study, we investigated which root trait(s) drive sediment stability (resistance to lateral erosion) in two marsh species with an important role in coastal protection (Spartina anglica and Atriplex portulacoides) and how the environment affects the expression of these traits. We sampled three marshes along salinity gradients in each of two estuaries in Wales (UK), establishing replicate plots in the respective dominant zones of each species. In all plots we sampled abiotic variables (sand, redox potential, pH, salinity) and root traits (root density, specific root density, root volume, root length density); in a subset of these plots (three per species in each marsh) we extracted soil-plant cores and assessed their erosion resistance in a flume. Sediment stability was enhanced by increases in root density and reductions in sand content. Abiotic variables affected root density in different ways depending on species: in S. anglica, redox was the only significant factor, with a positive, linear effect on root density; in A. portulacoides, redox had a non-linear (U-shaped) effect on root density, while sand had a negative effect. Collectively, these results show that (i) intraspecific variability in root density can influence sediment stability in salt marshes, and (ii) sediment properties not only influence sediment stability directly, but also indirectly via root density. These results shed light on spatial variability in the stability of salt marshes to lateral erosion and suggest that root density should be incorporated into coastal vegetation monitoring programs as an easy-to-measure root trait that links the environment to sediment stability and hence to the function and services provided by marshes.