Produção da serapilheira e fluxo de carbono em um manguezal em processo de restauração ecológica no estuário do Rio Pacoti, Ceará

Abstract

Mangroves are highly productive ecosystems, effective in capturing and storing carbon, and play a crucial role in mitigating climate change. Nevertheless, information on carbon fluxes in Brazilian mangroves remains limited, particularly regarding the litterfall compartment. This study assessed litterfall production and its carbon input in a mangrove under ecological restoration, located in the Pacoti River estuary, Ceará, Brazil. Sampling was conducted from April to September 2024 in areas with distinct vegetation cover: two under restoration (Areas A and B) and two conserved (Areas C and D). Litter traps (1 m², n = 15) were installed 1.30 m above the ground, with a 2 mm mesh. Collected material was sorted into six categories: (1) leaves, (2) flowers, (3) fruits (including propagules), (4) stipules (by species), (5) branches and twigs, and (6) miscellaneous, then oven-dried at 60 °C until reaching constant dry mass. Carbon content was estimated from dry mass using species- and component-specific conversion factors. For branches, a general factor was applied, while stipules and miscellaneous fractions were excluded due to the lack of specific values. Annual litterfall production was estimated at 14.25 Mg ha⁻¹ yr⁻¹, with a carbon flux of 5.904 Mg C ha⁻¹ yr⁻¹. Conserved areas showed higher biomass and carbon inputs, whereas the least developed area (Area A) had the lowest values. Leaves represented the dominant fraction (68.7%), followed by fruits (11.2%) and branches (10.5%), with Rhizophora mangle contributing substantially to total biomass. No significant seasonal variation was observed in total litterfall production, except for fruits, which peaked during the rainy season, likely reflecting the reproductive cycle of species, particularly Laguncularia racemosa. Overall, litterfall represents a key pathway of carbon input into mangroves, and the studied area shows potential to contribute to organic matter accumulation and carbon cycling processes within the ecosystem.