Caractérisation des chutes de litière et des apports au sol en nutriments dans une mangrove de Guyane française

Abstract

Litter falls and their contributions to soil nutriments were measured in five distinct facies of a mangrove in French Guyana. These facies were characterized by their distance from the sea, their floral composition (Laguncularia racemosa (L.), Avicennia germinans (L.) Stearn, Rhizophora spp.), and their structural features. Data were analyzed according to facies and to species for litters, as well as to seasons for the nutriments. This mangrove produced respectively 8.8 and 8.7 t·ha–1·year–1 of litter at the pioneer and senescent stages submitted to strong environmental constraint and 12.5 and 12.6 t·ha–1·year–1 for young and mature stages where developmental conditions are optimum. Nitrogen and carbon inputs were estimated to 1.3 × 10–2 and 6.4 t·ha–1·year–1, respectively. Litter appeared rich in phosphorous, corresponding with the high concentrations characterizing the sediments. For a given species, magnesium and calcium concentrations were constant between facies, whereas potassium and sodium concentrations varied according to the distance from the sea. Differences were perceived between species for all nutriments except sodium. Results are discussed in relation with the ecophysiological characteristics of the mangrove trees and the specific sedimentology of Guyana coast and are replaced in the perspective of an improved knowledge of the carbon and mineral balances in tropical coastal ecosystems.Key words: mangrove, French Guyana, litter, carbon balance, mineral nutriments, spatial variations.[Journal translation]