Does salt stress constrain spatial distribution of dune building grasses Ammophila arenaria and Elytrichia juncea on the beach?

Marinka E B Van Puijenbroek,Noortje Meijdam,Juul Limpens,Frank Berendse,Corry Teichmann,Imma Oliveras

doi:10.1002/ece3.3244

Marinka E B Van Puijenbroek, Noortje Meijdam + Show 4 more

Open Access

https://doi.org/10.1002/ece3.3244

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Abstract

Rising sea levels threaten coastal safety by increasing the risk of flooding. Coastal dunes provide a natural form of coastal protection. Understanding drivers that constrain early development of dunes is necessary to assess whether dune development may keep pace with sea‐level rise. In this study, we explored to what extent salt stress experienced by dune building plant species constrains their spatial distribution at the Dutch sandy coast. We conducted a field transplantation experiment and a glasshouse experiment with two dune building grasses Ammophila arenaria and Elytrigia juncea. In the field, we measured salinity and monitored growth of transplanted grasses in four vegetation zones: (I) nonvegetated beach, (II) E. juncea occurring, (III) both species co‐occurring, and (IV) A. arenaria dominant. In the glasshouse, we subjected the two species to six soil salinity treatments, with and without salt spray. We monitored biomass, photosynthesis, leaf sodium, and nutrient concentrations over a growing season. The vegetation zones were weakly associated with summer soil salinity; zone I and II were significantly more saline than zones III and IV. Ammophila arenaria performed equally (zone II) or better (zones III, IV) than E. juncea, suggesting soil salinity did not limit species performance. Both species showed severe winter mortality. In the glasshouse, A. arenaria biomass decreased linearly with soil salinity, presumably as a result of osmotic stress. Elytrigia juncea showed a nonlinear response to soil salinity with an optimum at 0.75% soil salinity. Our findings suggest that soil salinity stress either takes place in winter, or that development of vegetated dunes is less sensitive to soil salinity than hitherto expected.

Highlights

Sea levels are predicted to rise with 26–82 cm in this century, due to climate change (IPCC, 2014)
We found in our glasshouse experiment that salt spray did not interact with soil salinity
We explored to what extent the species biomass responses to increasing soil salinity in the glasshouse could be attributed to nutrient limitation, osmotic stress, and ionic stress, as this could, perhaps, shed more light on species responses in the field

Summary

Introduction

Sea levels are predicted to rise with 26–82 cm in this century, due to climate change (IPCC, 2014). Rising sea levels may lead to higher frequency and intensity of flooding, emphasizing the need for flexible coastal protection (IPCC, 2014; KNMI & PBL, 2015). Once vegetation established on the beach, it captures wind-blown sand and forms an embryo dune ( known as an incipient dune; Hesp, 2002; Maun, 2009; Zarnetske et al, 2012). These vegetated embryo dunes may grow into foredunes that are known for their coastal protection function (Maun, 2009). As vegetation plays a key role in capturing and retaining sand, the position and rate of dune development on the beach are constrained by vegetation establishment and growth (Keijsers, De Groot, & Riksen, 2015; Zarnetske et al, 2012)

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