Dinâmica da liteira de mangal em duas áreas: Costa do Sol e Saco - Inhaca

Abstract

The rate of litter fall and leaf decomposition was estimated for Avicennia marina and Rhizophora mucronata in two study areas of the Maputo Bay: Costa do Sol and Saco da ilha de Inhaca, with the aim of determining productivity. The study areas were chosen considering their proximity to the urban centre. Baskets of 0.25 m area and 1 mm2 mesh size were used to estimate litter fall rate, while leaf litter bags of 150 mm x 150 mm x 250 mm were used to estimate leaf decomposition rate. The baskets were securely tied to the branches at a height of 2 m above the ground to prevent them from getting wet, while the detritus bags were securely tied to the pneumatophores but touching the sediment surface. The two experiments were conducted over 56 days with periodic 15-day sampling for both study sites. Productivity of mangai at Costa do Sol was low, because trees grow little and the number of individuals is small, while Saco da Inhaca recorded higher daily rate of litterfall for R. mucronata, (10.64 g/m ) than for A. marina (4.64 g/m ). Leaf fall contributed most to the total litter produced with about 80%, while floral forms and propagules were not observed because their production is seasonal. Leaf fall was significantly higher for R. mucronata, (31.09 g/m2) compared to A. marina (14.99 g/m ) while stem fragment fall did not differ significantly between the two species. The decomposition rate of A. marina leaves was higher than that of R. mucronata leaves in both sampling areas although there were no significant differences between the species in the two study areas. However, it was possible to conclude that the Saco of Inhaca Island was found to be more productive than the Costa do Sol and A. marina leaves decomposed faster than R. mucronata leaves at both study sites.(TRADUÇAO NOSSA)