Seed bank dynamics of the annual halophyte Salicornia ramosissima: towards a sustainable exploitation of its wild populations

Abstract

Halophytes are able to survive in the high salted areas of the world, and have been recognized as sources of bioactive metabolites. There is a need to design sustainable strategies for the use of wild populations of halophytic species in order to avoid irrational gathering. Seed banks are essential for resilience and regeneration in salty ecosystems. We sampled annual seed production, aerial and soil seed banks and seed dynamics for a year in four wild populations of the annual halophyte Salicornia ramosissima growing in saltpans, in order to develop sustainable management practices for the use of its populations.The seed production of S. ramosissima depended mainly on plant density rather than on the number of seeds produced by each individual plant. In three of the four study populations, most of the annual seed production was exported out of the saltpans (> 79%) and only between 14-20% was accumulated in the initial aerial and soil seed banks. These initial seed banks were highly depleted during the year until the next fruiting period, when they accumulated less than 1% of the annual seed production (from 19 to 15302 seed m − 2 ). Salicornia ramosissima established a persistent soil seed bank in two of the four locations. Annual seed production would be key for the preservation of those S. ramosissima populations that do not establish persistent soil seed banks. In view of our results, each population of S. ramosissima should be studied independently to design population-speci c management plans.

Population Dynamic of the Annual Halophyte Salicornia ramosissima in Salt Pans: Towards a Sustainable Exploitation of Its Wild Populations

“…Therefore, this temporal pattern of germination may allow some S. ramosissima plants to avoid catastrophic events, such as herbivory or violent river floods, that could impact its populations throughout the growing season. Even so, the S. ramosissima seed bank was drastically reduced during the first year after seed dispersal [8], as occurred in S. europaea [19]. Additionally, all study populations presented similar plant height that was unrelated to plant density, so it seems to be linked to particular habitat characteristics or/and genetic differentiation, as demonstrated in S. europaea using transplant experiments [23,27,32].…”

“…In contrast, S. ramosissima populations colonizing frequently waterlogged depressed zones presented five-times greater soil-seedbank densities and maximum plant densities (between 1257 and 51,558 plants m −2 ) than populations in elevated zones. These high seed-bank densities may be the result of higher in situ seed production [8] and the transport of seeds from elevated to depressed zones. Previous studies have reported a positive correlation between soil-seed-bank density and plant density for S. ramosissima [8] and S. europaea [19].…”

“…These high seed-bank densities may be the result of higher in situ seed production [8] and the transport of seeds from elevated to depressed zones. Previous studies have reported a positive correlation between soil-seed-bank density and plant density for S. ramosissima [8] and S. europaea [19]. In our context, populations in depressed zones lost c. 60% of their maximum plant densities from the end of spring and throughout summer.…”

“…Most halophytes are perennials, but some halophyte species are annuals [7]. Planning the extraction of individual plants from wild populations in a sustainable way is especially important in the case of annual halophyte species, since their populations are generated each year from pre-existing seed banks [8]. To our knowledge, no previous study has analyzed the population dynamic of annual halophyte species to develop sustainable management practices.…”

“…Woods colonizes European and North African salt marshes, occurring in a wide range of habitats [16], including salt pans, since their seeds are able to germinate at hypersalinity [17,18]. The seed production of S. ramosissima mainly depends on plant density rather than on the number of seeds produced by each individual plant and its soil seed bank, which is drastically reduced, even totally depleted, during the first year after seed dispersal [8], as has been reported for Salicornia europaea L. [19].…”