Modelling soil organic carbon distribution in two Farasan mangrove species

This study examined the distribution of soil organic carbon (SOC) storage in two mangrove species, Avicennia marina and Rhizophora mucronata, across fourteen distinct sites along the coastline of Saudi Arabia’s Farasan Islands. Three statistical models—allometric, exponential, and sigmoid—were employed to analyze soil carbon data obtained from twenty-one soil cores, resulting in a dataset of 210 soil samples per species. To better understand the role of mangroves in carbon storage, we aimed to develop models capable of predicting the distribution of cumulative SOC stocks and volumetric SOC densities throughout soil profiles, accounting for both species and depth variations. The sigmoid model proved most effective in forecasting volumetric SOC density, achieving average R² values of 0.58153 for A. marina and 0.82103 for R. mucronata. For A. marina, all three models accurately estimated cumulative SOC stocks, with the allometric model showing the highest performance (R² = 0.99999). In the case of R. mucronata, both the allometric and exponential models were applicable, with the exponential model demonstrating superior accuracy (R² = 0.99996). Consistent with the established role of plant cycling in carbon sequestration, both mangrove species exhibited higher SOC content in the topsoil, with topsoil carbon fractions (TCFs) exceeding 0.10. These findings significantly enhance our understanding of SOC distribution in mangrove ecosystems and support more informed projections of future carbon stocks for conservation and restoration planning.