Determination of different SOC-focused biogeographic regions using the GIS-based SWARA method and soil organic carbon stock variation

The present study aimed to assess the potential of biogeographic regions focused on soil organic carbon within the Eastern Black Sea Sub-Region and the Konya sub-region of Türkiye. These Sub-Regions have various unique distinct physical geographical properties (climate, geomorphology, vegetation, hydrology, etc.), land use-land cover, and soil geography characteristics. The present study evaluates their capacity to produce their soil organic carbon (SOC) using the Stepwise Weight Assessment Ratio Analysis (SWARA) method. Because numerous environmental factors influence the potential for SOC production in various SOC-driven biogeographic zones, the degree to which these criteria influence and contribute to the creation of SOC varies. Determining these criteria's relative relevance is a difficult decision-making process. One strategy created to get around this challenge is the SWARA method. Additionally, soil organic carbon stock calculations were made in soil samples (3,440) taken from both sub-regions to validate model outputs obtained, and their spatial changes were compared with the model output. According to the results, the lowest RMSE values of interpolation models for Eastern Black Sea and Konya biogeographic sub-regions were determined 0.103 (Gaussian semivariogram model of Ordinary Kriging) and 0.474 (IDW-2). As for the SWARA model, it was found that the highest weighting value was for vegetation intensity whereas, pH sub-crietria has the lowest weighting value as 0.011. Moreover, while soil organic carbon contents of soils distributed in the Eastern Black Sea biogeographic sub-region vary between 19.52 tons C ha⁻¹ and 156.32 tons C ha⁻¹, they vary between 11.85 tons C ha⁻¹ and 99.55 tons C ha⁻¹ for the Konya biogeographic Sub-region. When the statistical relationship between soil organic carbon stock values and model results in soil samples taken from the sub-regions were checked for accuracy of the result obtained from estimation model, very high coefficient of determination (R²) values, such as the R² value of 0.699 for the Eastern Black Sea biogeographic Sub-Region, and the R² value of 0.697 for the Konya biogeographic sub-region, were found.