Abstract
Salt marshes, providing numerous ecosystem services, are degrading worldwide. To effectively aid conservation and restoration efforts, increased knowledge on marsh expansion processes and the initial establishment of pioneer vegetation is essential. In this study, we disentangle environmental drivers that affect the lifecycle of the annual pioneer Salicornia procumbens at the salt marsh edge. We studied the effect of various environmental variables on the start of germination, germination success and mortality before seed-set in a field experiment in the Dutch Wadden Sea at Westhoek. Our results indicate that temperature and sedimentation inhibited the initiation of germination. Once germination occurred, higher precipitation rates increased germination success. In contrast, sedimentation rates above 0.5 mm day−1 halved germination success through burial of freshly sprouted seedlings. Unexpectedly, natural germination was low, indicating that seed availability may have been limited, despite a seed source nearby. Frequent inundation, extended periods without inundation (through desiccation of the soil) and a highly dynamic bed level increased mortality before seed-set. Consequently, bed-level dynamics (erosion, sedimentation and bed-level variation) impact seed production dually (decrease germination and increase mortality) and thus potentially reproduction success. A high seed reproduction is crucial for annuals, such as S. procumbens, to re-establish the following year. Next to advancing our general knowledge of natural salt marsh expansion, results in this study can also be used to assess the potential of a given site for salt marsh stimulation or restoration. Seed availability and local bed-level dynamics are key in the successful establishment of a salt marsh pioneer: Salicornia procumbens.
Highlights
Salt marshes and intertidal flats are essential parts of coastal systems that provide protection against floods through wave attenuation (Schuerch et al 2014; Temmerman et al 2013)
Supplying seeds led to an increase of S. procumbens individuals in the transition zone, at both the vegetation edge and the intertidal flat (Fig. 2)
The aim of this study was to identify the environmental variables that determine the establishment success of the annual S. procumbens in the transition zone located between salt marsh and intertidal flat (Figs. 2 and 3)
Summary
Salt marshes and intertidal flats are essential parts of coastal systems that provide protection against floods through wave attenuation (Schuerch et al 2014; Temmerman et al 2013). They are vital habitats for migratory and breeding birds and Communicated by Charles T Roman. Most research is restricted to the germination phase of pioneer plants (Carter and Ungar 2003; ElseyQuirk et al 2009; Khan et al 2000; Noe and Zedler 2001), whereas understanding seedling establishment and mortality before seed-set is important
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