Structure, floristic composition, aboveground biomass and carbon stock, in Laguna de Gandoca and Estero Moín mangroves, Limón, Costa Rica.

Abstract

The area of two Southern Caribbean mangroves of Costa Rica was delimited. Horizontal and vertical structure, floristic composition, above-ground biomass and carbon stock were analysed in respect to the distance gradient from the channel edge. Circular plots of seven meter radius were established every 25 m on perpendicular transects from the channel edge. Tree diameter (d) of each individual ≥ 5 cm was measured. In each plot the following parameters were calculated: tree density (n/ha), basal area (m2/ha), diameter class distribution of individuals, total height (m), tree densities per height storey, importance value index of species (IVI), Shannon–Wiener (H´) diversity index, Fisher Alpha diversity index, above-ground biomass and carbon stock. An incomplete random block experimental design (IRBD) was employed for the statistical analysis. The mangrove surface areas were 13,34 ha and 10,73 ha for Gandoca and Moín respectively. The tree average diameters were 21,43 cm and 20,01 cm, while the total tree height were 12,8 m and 10,5 m, with tree densities of 687 n/ha and 708 n/ha, and basal areas ranging 26,35 m2/ha and 26,37 m2/ha in Gandoca and Moín sites respectively. The most important specie in Gandoca was Rhizophora mangle and Pterocarpus officinalis in Moín. Laguncularia racemosa and Avicennia germinans with 20 other associated species were also observed in both sites. Moín was the most diverse one. The biomass was 330,27 Mg/ha and 257,10 Mg/ha while the carbon stock was 183,47 Mg/ha and 237,36 Mg/ha, for Gandoca and Moín respectively. Floristic composition and structure were similar to those reported in the Caribbean and suggest that both sites are mature and in constant renewal; however Moín shows some disturbance. The biomass and carbon stocks are higher than those reported for secondary and primary forests of Costa Rica and also for other mangroves of the Indo - Pacific. The mangrove of Gandoca showed an area increment. The Moín mangrove has not information about area variation because there was no previous estimation of surface area.