Organic carbon stock between different grain sizes in Arenosols from the coastal dunes of Campeche Bay, Mexico

Coastal sandy soils are dynamic, and so estimating their organic carbon sequestration capacity is crucial for restoration for the restoration of coastal ecosystems. We assessed the distribution of soil organic carbon stock between three grain sizes (1000, 500, and 250 μm) and three erosion conditions (low, medium and high) in sandy soils (Arenosols) on the coastal sand dunes of Campeche Bay. We analyzed particle size distribution, aboveground and belowground biomass, organic matter and the soil organic carbon contained in 1000, 500, and 250 μm grain size. Very coarse, coarse, and medium sand grains predominate on coastal dunes. Rhizomatous roots prevailed in the supratidal zones and were absent in the infratidal zones with high erosion. Soils under low erosion conditions maintained high organic carbon contents, highlighting the contribution of very coarse grains (1000 μm) for organic carbon sequestration. In conclusion, carbon sequestration is mainly associated with grain size – medium sand stores over 60 C ton/ha - and the contribution of both aboveground and belowground biomass, particularly rhizomatous roots, which play a crucial role in mitigating coastal erosion. Our findings suggest the need to focus our efforts on restoring coastal dunes given the provision of environmental services and high vulnerability to climate change.