Distribution of soil organic carbon in the mangrove Avicennia marina (Forssk.) Vierh. along the Egyptian Red Sea Coast

The objectives of present study are: (1) to quantify the vertical distribution of the soil bulk density (SBD), soil organic carbon (SOC) content and SOC density in the soil of the mangrove forests in comparison with a reference site along the Egyptian Red Sea Coast; (2) to provide estimates of the carbon sequestration rate (CSR) and the carbon sequestration potential (CSP) of mangrove forests in Egypt; and (3) to establish a baseline data on SOC pools for future studies on SOC dynamics. Sampling was carried out in three stations along the Egyptian Red Sea Coast. The sampled station were classified to mangrove and reference (mud flat) stands. In each of the sampling station, five sampling sites were selected to assure representative samples to each of the mangrove and mud flat stands. Three soil cores were taken in each sampling site and were pooled together into one composite core per sampling site. In total, 120 soil samples were collected, i.e., one sample from each four soil layers (0-10, 10-20, 20-30 and 30-40 cm) at each of the 30 sampling sites (15 sampling sites per each of mangrove and mud flat stands). The mean distribution of SBD in the mangrove and mud flat stands increased significantly with depth. SOC content in the mangrove stands declined significantly with depth from 20.0 g C kg−1 at depth 0-10 cm to 11.4 g C kg−1 at depth 20-30 cm. SOC content in the mud flat stands declined significantly with depth from 9.0 g C kg−1 at depth 0-10 cm to 1.9 g C kg−1 at depth 30-40 cm. The stand type affected significantly the SOC pool, where the total mean of SOC pool of the mangrove stands (8.5 kg C m−2) was higher than that of the mud flat stands (2.6 kg C m−2). The average CSR of the mangrove stands (6.1 g C m−2 year−1) was higher than the mud flat stands (2.0 g C m−2 year−1). Based on the area of mangrove stands (525 km2) and CSR, the total CSP of mangroves in Egypt was 3.17 ± 0.05 Gg C year−1.