MEPS 616:51-65 (2019)  -  DOI: https://doi.org/10.3354/meps12943

ABSTRACT: Seed banks are key for resilience, secondary succession and restoration in ecosystems, especially in stressful environments. Even though salt marshes are an excellent ecosystem for studying seed bank dynamics along environmental stress gradients, few studies have analyzed these aspects on the entire intertidal gradient in the plant community as a whole. We recorded the density, species composition and distribution of sexual propagules, considering total number and only those propagules that contained seeds with an intact embryo, along the intertidal gradient in salt marshes (Ría Formosa, southwest Iberian Peninsula). The propagules mostly accumulated in the ecotone between the salt marshes and coastal dunes, acting as sink habitat. Beyond this, the highest densities of propagules were recorded in less stressful habitats. The most abundant propagules were usually found close to seed plant sources. Halophytes located along the intertidal gradient presented 3 different dispersal behaviors: short-distance dispersal, medium- to long-distance dispersal and a mix of both. A total of 12 of the 18 recorded propagules formed transient seed banks, reflected in lower species richness and diversity in the seed bank than in the established vegetation. Six taxa formed persistent seed banks, showing seeds with intact embryos throughout the year. Our results indicate that the persistent seed bank did not play an important role in sustaining the diversity of halophytes in the studied marshes. Their resilience mainly relied on seed dispersal, not on in situ germination from the seed bank.

KEY WORDS: Tidal salt marsh · Plant zonation · Dispersal · Persistent seed bank · Ría Formosa