Will restored mangrove forests enhance sediment organic carbon and ecosystem carbon storage?

Mangrove forests are among the largest carbon (C) sinks in (sub) tropical areas, playing a vital role in reducing C emissions. However, these forests have degraded rapidly in recent decades due to various human activities and natural disturbances. Thus, mangrove restoration programs have been widely initiated to prevent further forest loss and to mitigate climate change. The measurement of ecosystem C storage in restored mangrove forests will provide crucial information for the temporal reporting of C emissions in reducing emissions from deforestation and forest degradation (REDD+) schemes. The question whether restored mangrove forests enhance sediment organic carbon (OC) and ecosystem C storage has not been resolved for mangrove restoration programs. The present study, therefore, aimed to quantify ecosystem C storage and the contribution of organic matter sources to sedimentary OC in Kandelia obovata forests aged 9, 19 and 27 years; Sonneratia caseolaris forests aged 2 and 3 years, and a reference mudflat forest aged 0 from Hau Loc, North-Central Vietnam. The mean above- and below-ground C stocks of these forests ranged from 12.7±2.4 to 107.5±10.7MgCha−1, and 103.8±2.9 to 412.4±6.5MgCha−1, respectively. The ecosystem C storage of mangrove forests tended to increase with stand age, ranging from 201.3±4.3 to 519.9±12.5MgCha−1, with an overall mean of 310.3±21.3MgCha−1. The contribution of mangrove litter to sedimentary OC was between 45.8±0.8 and 64.1±1.5% along a forest chronosequence. The increase of the OC content and ecosystem C storage, and the proportional contributions of OC sources with forest age resulted from higher biomass production following forest development and the location of stands in the intertidal zone. These findings highlighted the importance of mangrove restoration programs in enhancing the ecosystem C storage and the sediment OC.