Negative Correlation between Soil Salinity and Soil Organic Carbon Variability

Soil Organic Carbon (SOC) is vital for terrestrial ecosystems, affecting biogeochemical processes, and soil health. It is known that soil salinity impacts SOC content, yet the specific direction and magnitude of SOC variability of in relation to soil salinity remain poorly understood. Analyzing 43,459 mineral soil samples (SOC < 150 g kg-1) collected across different land covers since 1992, we approximate a soil salinity increase from 1 to 5 dS m-1 in croplands would be associated with a decline in mineral soils SOC from 0.14 g kg-1 above the mean predicted SOC ( = 18.47 g kg-1) to 0.46 g kg-1 below (~-430%), while for non-croplands, such decline is sharper, from 0.96 above = 35.96 g kg-1 to 4.99 below (~-620%). Although salinity’s significance in explaining SOC variability is minor (< 6%), we estimate a one std increase in salinity of topsoil samples (0 - 7 cm) correlates with respective declines of ~4.4% and ~9.26%, relative to and . The decline in croplands is greatest in vegetation/cropland mosaics while lands covered with evergreen needleleaved trees are estimated with the highest decline in non-croplands. We identify soil nitrogen, land cover, and precipitation Seasonality Index the most significant parameters in explaining the SOC’s variability. The findings provide insights into SOC dynamics under increased soil salinity, enhancing our understanding of SOC stock responses to land degradation and climate warming.The data provided in this dataset forms the foundation for the aforementioned results and helps in replicating the output.