Marchand Cyril. (2017). Soil carbon stocks and burial rates along a mangrove forest chronosequence (French Guiana). Forest Ecology and Management, 384, p. 92-99. ISSN 0378-1127.
Source
Forest Ecology and Management, 2017,
384, p. 92-99 ISSN 0378-1127
Mangroves provide a range of important ecosystem services, notably being efficient blue carbon sinks. In addition to their CO2 fixing ability, these coastal tropical forests can store large amount of carbon in their soils due to waterlogging inducing slow rates of organic matter (OM) decomposition. The French Guiana coastline is a highly dynamic environment, characterized by a series of migrating mudbanks. Within this specific sedimentological context, only A. germinans propagules can develop at the highest elevation of mudbanks that are stabilized only for a few decades before being eroded. As a result, a clear zonation pattern, with mangrove stands of different ages paralleling the shoreline, allows the study at the same time of A. germinans forests from pioneer to mature and senescent stands. The unique characteristic of this system is the isolation of the older mangroves from the sea, being situated more than 2 km from the shoreline, which limits sedimentation and allochthonous inputs. Within the studied chronosequence, soil carbon stocks and carbon burial rates of each mangrove stand were determined. The thickness of the pedogenetic layer, enriched in autochthonous OM, reached an asymptote (similar to 45 cm) for the mixed mature and senescent forests (>40 years old), probably as a result of the asymptote reached by the net primary productivity (NPP) and low sedimentation rates. The organic carbon stock in the pedogenetic layers increased linearly with forest age, from 4 to 107 Mg OC ha (-1) in pioneer and senescent stages, respectively. Consequently, considering only the pedogenetic layers, enriched with the OM derived from the current forest, soil organic carbon (SOC) stocks are limited. It is suggested that tidal export of the NPP may balance low mineralization rates induced by waterlogging, at least for the stand the closest to the sea. The mean carbon burial rate for this system was 2.3 Mg OC ha(-1) yr(-1), with values ranging from 0.72 to 4.86 Mg OC ha (-1) yr(-1) depending on forest age and position of the stand in the tidal zone. The latter, either promoting tidal flushing and tidal pumping on the seaward side of the mangrove, or the development of associated mangrove species on the landward side due to freshwater proximity and low sedimentation rates, influenced organic accumulation in soils.
