Etude in situ de la réinstallation d'un peuplement sciaphile de mode battu après sa destruction expérimentale, en Méditerranée

Abstract

The structure (internal organization) of the biocoenosis of the shady and wave-lashed bottoms in the western Mediterranean Sea is very heterogeneous. Little is known concerning the causes of this heterogeneity. For analyzing the composition of the vegetation, the survey method of Braun-Blanquet (1964) was used. Reconstruction of the biocoenosis on cleaned rocky surfaces follows a definite pattern as a function of time. After 4 months, the rocky surface is covered with the crustaceous alga Dermatolithon hapalidioides. After 6 months, various dendristic and fruticose algae settle on D. hapalidioides, mainly Pseudochlorodesmis furcellata, Petroglossum nicaeense and Myriogramme minuta. After 1 year, the whole area is occupied by P. nicaeense, Plocamium vulgare and Valonia utricularis; the undergrowth consists of D. hapalidioides which becomes slowly superseded by fruticose algae. This sociological progression shows that: (1) The phases during reconstruction of the settlement are equivalent to the structural elements of the initial settlement; (2) perhaps the structural organization results from a chronological sequence of different phases; (3) reconstruction of the initial settlement after experimental destruction is very rapid. © 1973 Biologischen Anstalt Helgoland.