Abstract
Abstract. The persistence of tidal wetland ecosystems like salt marshes is threatened by human interventions and climate change. In particular, the threat of accelerated sea level rise (SLR) has increasingly gained the attention of the scientific community recently. However, studies investigating the effect of SLR on plants and vertical marsh accretion are usually restricted to the species or community level and do not consider phenotypic plasticity or genetic diversity. To investigate the response of genotypes within the same salt-marsh species to SLR, we used two known genotypes of Elymus athericus (Link) Kerguélen (low-marsh and high-marsh genotypes). In a factorial marsh organ experiment we exposed both genotypes to different flooding frequencies and quantified plant growth parameters. With increasing flooding frequency, the low-marsh genotype showed higher aboveground biomass production compared to the high-marsh genotype. Additionally, the low-marsh genotype generally formed longer rhizomes, shoots and leaves, regardless of flooding frequency. Belowground biomass of both genotypes decreased with increasing flooding frequency. We conclude that the low-marsh genotype is better adapted to higher flooding frequencies through its ability to allocate resources from below- to aboveground biomass. Given the strong control of plant biomass production on salt-marsh accretion, we argue that these findings yield important implications for our understanding of ecosystem resilience to SLR as well as plant species distribution in salt marshes.
Highlights
Salt marshes are wetland ecosystems predominantly found along coastlines, where they form a transition zone between the marine and the terrestrial environment
Plants were collected in April 2015 from a salt marsh on the Dutch island Schiermonnikoog (53◦30 N, 6◦16 E) from stands that have previously been identified to be dominated by genetically distinct populations of E. athericus, i.e. highmarsh (HM) and low-marsh (LM) genotypes (Bockelmann et al, 2003)
The low-marsh genotype generally formed longer rhizomes, shoots and leaves, regardless of flooding frequency (Figs. 1 and 2). We argue that these findings yield important implications for our understanding of ecosystem resilience to sea level rise (SLR) as well as plant species distribution in salt marshes
Summary
Salt marshes are wetland ecosystems predominantly found along coastlines, where they form a transition zone between the marine and the terrestrial environment. Salt marshes provide important ecosystem services like protection of coastlines against storm surges by wave attenuation (Möller et al, 2014), supply of nursery grounds for commercially important fish (Bolle et al, 2009) and mitigation of climate change by long-term carbon sequestration (McLeod et al, 2011). Up to a certain locally varying threshold of SLR, salt marshes are able to keep up with rates of SLR through their ability to accrete vertically (Kirwan and Megonigal, 2013) During this process, salt-marsh plants act as ecosystem engineers because their aboveground biomass reduces water flow velocity and hydrodynamic forces, which results in a decrease in the sediment-loading capacity of the water and an increase in sediment settlement (Morris et al, 2002; Yang, 1998).
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