Modelling the distribution pattern of soil organic carbon in protected and grazed areas of mangrove forests (Avicennia marina)

Abstract

The primary aim of the current study was to develop a model capable of predicting the spatial distribution patterns of soil organic carbon (SOC) in mangrove forests (Avicennia marina) affected by camel grazing along the southern coast of the Red Sea. Four protected locations within mangrove forests were selected along the southern coast of the Saudi Red Sea, while eight other locations were selected under the influence of camel grazing. Three equations—allometric, exponential, and sigmoid—were employed on soil carbon data obtained from 40 soil cores, which equated to 600 soil samples. The goal was to develop models that could forecast how the cumulative SOC stocks (SOCc) and volumetric SOC densities (SOCv) would be distributed throughout the respective soil profiles in protected and grazed locations of mangroves, in order to predict how soil carbon changes when mangroves are under grazing stress. The sigmoid and exponential equations proved to be most effective in predicting SOCv distribution, with average R2 values of 0.956681 and 0.893894 for protected and grazed locations, respectively. For protected locations, all three equations effectively predicted the SOCc, with the sigmoid equation (R2 = 0.999942) exhibiting the best performance. In grazed locations, all equations were applicable, with the allometric equation demonstrating superior accuracy (R2 = 0.999910). The study found that grazing activities in mangrove forests resulted in a loss of SOC stock of 7.0 kg C/m2, accounting for 54% of the initial stock. These findings will significantly enhance our comprehension of SOC distribution in mangrove ecosystems under the grazing effect, allowing us to quantify the impact of camel grazing on SOC dynamics in coastal ecosystems.

Keywords

• Blue carbon
• Mathematical functions
• Carbon reserves
• Camel grazing
• Validation indices
• Vertical distribution