Soil seed bank and community dynamics in an annual-dominated Mediterranean salt-marsh

The seed bank in the soil and litter of an annual grassland in the upper salt marsh of the Guadalquivir delta (SW Spain) contained on average 49 110 seeds/m2; 29 species were represented. Field censuses of the grassland, in two consecutive springs, yielded 7 410 and 9 520 plants/m2 respectively. A combined Correspondence Analysis of the seed bank samples and field censuses showed differences in grassland composition between wet and dry years. The environmental changes induced different expressions of the soil seed bank, mediated by demographic processes. The effect of salinity (25 dS/m of NaCl) was studied on intact soil blocks transplanted to a greenhouse. Salinity did not affect the emergence of seedlings, but reduced the growth of the dominant species, Trisetaria panicea. The importance of the role of seed banks in community dynamics and their use for conservation management are discussed.