Evolution récente de la végétation intertidale du Delta de l'Eyre

La végétation des schorres du delta de l'Eyre est présentée d'après un travail récent de Soriano-Sierra (1992). la composition de la flore et son évolution spatio-temporelle sont décrites et des comparaisons établies entre 1964 et 1988. Les peuplements végétaux halophiles de la haute slikke et du schorre progressent au niveau du distributaire principal de l'Eyre dans le Bassin, tandis qu'ils sont érodés ou stables dans les autres régions du delta. Les auteurs signalent enfin le développement récent de Spartina x townsendii et de deux Ulvacées envahissantes Enteromorpha clathrata et Ulvaria obscura. Les schorres du delta de l'Eyre devraient être cartographiés avec précision car ils ont fait l'objet d'une protection règlementaire récente.


Végétation, zone intertidale, delta

Maritime salt-marshes of the Eyre's delta located in Arcachon Bay (South-West Atlantic coast of France) were studied following to a recent work of Soriano-Sierra (1992). In the se tidal areas salt marshes develop at the top of mud-flats covered by Zostera noltii beds, and in the vicinity of fish ponds who are lagoonal impoundments of the 18th century. Along the Eyre's estuary where salinity is reduced by seepage of fresh water from the land, Spartina maritima and other halophilic plants tend to be replaced by a taU marsh of Phragmites communis, Scirpus maritimus and Juncus gerardii. The number of species or species richness is varying: S = 21 in the area l ("La Boucle") S = 26 ("Malprat") and S = 24 ("Comprian"). Rare species are present like Spartina versicolor or Sarcocornia froticosa. There is an increase of the salt-marshes in this area from 1964 (97,6 ha) to 1988 (108,4 ha) with a formation by sedimentation on the delta front. Erosion occurs also at the ground-like of the dykes, locally. Recently (1989) the new vigorous Spartina x townsendii colonized mud-flats, but the population level is actually very low, perhaps on account of the fresh water flows in winter and spring. We noted also an extensive growth of ulvoid green algae Enteromorpha clathrata and Monostroma obscura since 1982 and 1989 in the delta and the Arcachon Bayon tidal fIats, along the year for Monostroma and in summer only for Enteromorpha. Fertilized outwash from arable farming (maize) should cause this luxurious growth, but it is possible that other ecological and genetic factors cause the extensive growth of these algae. The salt-marshes are not very attractive for re-creation and tourism, except for the hunting, protection of the se areas was decided recently and mapping the variety in the vegetation should be carried out at different scales.


Vegetation, delta, schorre

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Labourg Pierre Jean, Soriano-Sierra Eduardo-Jean, Auby Isabelle (1995). Evolution récente de la végétation intertidale du Delta de l'Eyre. Actes de colloque Parc Naturel des Landes de Gascogne, Le Teich, 21-23 octobre 1993. https://archimer.ifremer.fr/doc/00152/26284/

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