Spatial distribution and stoichiometric characteristics of the topsoil macronutrients in the Sundarbans

This study investigated the status, distribution, and ecological stoichiometric characteristics of organic carbon (OC), total nitrogen (TN), total phosphorus (TP) and total sulfur (TS) of the surface soil (0–5 and 5–10 cm) collected from the Sundarbans mangrove forest in Bangladesh. Fifty-nine soil samples were collected from the four administrative ranges such as Satkhira, Khulna, Sarankhola and Chandpai of Sundarbans. The study witnessed that salinity greatly influenced the availability, distribution and stoichiometry of soil OC, TN, TP, and TS. The OC and TN contents were found to increase with decreasing the salinity level probably due to the increasing soil microbial activity from higher to lower salinity levels. The TP content was recorded higher in moderate salinity levels where TS content was higher in moderate to low salinity levels. The OC, TN and TP contents of the top 0–5 cm of soil were recorded higher than 5–10 cm among the sampling ranges while TS content showed a reverse distribution. The stoichiometric ratios of C: N hardly varied along with the salt gradient, however, values of C: P and C: S appeared higher when the salinity level was higher. The OC and TN showed a significant positive relationship with OM and cationic contents. The stoichiometric ratios C: N, C: S, and C: P were either uncorrelated or moderately correlated; however, significantly positively correlated with OC and TN (p < 0.001). In addition to salinity levels, tourism reveals a positive effect on the distribution of organic carbon (OC) and total nitrogen (TN), but did not show any influence on the distribution of total phosphorus (TP) and total sulfur (TS). This study illustrates the distribution pattern of topsoil nutrients and their stoichiometric ratios derived from spatially distributed samples, offering baseline data for the formulation of policy and management strategies for the Sundarbans mangrove forest.