Aboveground carbon stock in a restored neotropical mangrove: influence of management and brachyuran crab assemblage

Abstract

Mangrove forests are important sinks of atmospheric carbon, and the internal deposits and fluxes of organic matter can reflect how these ecosystems respond to disturbances and environmental changes. Data on carbon content of mangrove forests vary geographically due to differences in abiotic (climate, geomorphic settings, tides) and biotic (diversity, herbivory, bioturbation) conditions. Mangroves have been degraded worldwide and ecological restoration is an alternative to recover these ecosystems and their functionality. However, although growing and biomass after disturbances have been addressed, studies on the recovery of faunal groups are rare. The brachyuran crab assemblage is strongly integrated to carbon recycling and ecosystem functioning, since propagule consumption and fossorial activity can affect the diversity and biomass of mangroves. We assessed the aboveground biomass and carbon stock of differently managed mangrove areas in northeastern Brazil, after being deforested for shrimp culture and then abandoned, and compared data with other forests worldwide. After a decade, the area restored with Rhizophora mangle showed higher carbon stock than the self-recovered forest and similar amount as an older forest. We discuss the applied rehabilitation measures regarding the effects of management and brachyuran crabs on forest aboveground carbon storage. The effects of herbivory and bioturbation of brachyurans on the low recruitment of Laguncularia racemosa propagules, contributed to higher biomass levels in the restored forest through reinforcing the predominance of R. mangle, which stocks more aboveground carbon with respect to Laguncularia. This suggests that the particularities of target tree species and brachyuran assemblage need to be considered in mangrove restoration, since they are related to function recovering and carbon cycling in the ecosystem.