Seed ecology of Mediterranean hind dune wildflowers

Indeed the seed vertical distribution plays a crucial role in the germination dynamics on buried seeds. The vertical distribution of the seed bank of 20 selected species was confined to the upper 0-12 cm layer of sand dune. Their burial depth was found to be inversely related to the 1000 seed weight of the different species ranging by 0.01 g of Centaurium maritimum to 47.58 of C. soldanella. Roughly 80% of the seed bank is accumulated in the shallowest sand layer (0-3 cm) and the only very little seeds of C. maritimum and Silene colorata were capable to reach the deeper layer of 9-12 cm. Seedling emergence from increasing burial depth has been studied in pots “ex situ”. In spite of the respective seed dormancy-breaking treatments, their germination was progressively inhibited by burial depth increasing in the sand matrix. Calculation of the depth able to halve emergence established an inverse relationship between seed weight and depth-mediated inhibition. In addition, the ex situ capacity for self-burial (mediated by winter rains), ranging between 1 and 3.5 cm, showed a similar, but inverse, relationship between seed weight and self-burial performance. Seed bank of herbaceous perennial species appears to be a good indicator of an ecosystem's health and the perspective of environmental restoration, by using native wildflowers, should be carried out by sowing treated seeds, with a light burial, behind the natural or artificial foredunes.