STRUCTURE, ABOVEGROUND BIOMASS AND DYNAMICS OF MANGROVE ECOSYSTEMS - NEW DATA FROM FRENCH-GUIANA

The article presents new results on the structure and the above-ground biomass of the various population types of mangroves in French Guiana . Nine mangrove stands were studied, each composed of three to ten adj oining plots with areas that varied depending on the density of the po pulations. Structural parameters and indices were calculated. Individu als representative of the three groups of taxa present were felled: Av icennia germinans (L) Steam, Rhizophora spp., and Laguncularia racemos a (L) Gaertn. The trunks, branches and leaves were sorted and weighed separately. The biomass was obtained by determining the allometric rel ationships, the general equation selected being of the type y = a(o)x( a1), where the diameter (x) is the predictive variable. The total abov e-ground biomass varied from 31 t ha(-1) for the pioneer stages to 315 t ha(-1) for mature coastal mangroves, but with large variations depe nding on the structural characteristics at each site. The results plac e the Guianese mangroves among those with high biomass, although lower than those reported for Asia. Based on the relationships between stru ctural parameters and standing biomass, in particular with the use of the ''self-thinning rule'', population dynamics models are proposed.