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 in relation to soil salinity remain poorly understood. Analyzing 43,459 mineral soil samples (SOC < 150 g kg ) collected across different land covers since 1992, we approximate a soil salinity increase from 1 to 5 dS m in croplands would be associated with a decline in mineral soils SOC from 0.14 g kg above the mean predicted SOC ([Formula: see text] = 18.47 g kg ) to 0.46 g kg below [Formula: see text] (~-430%), while for noncroplands, such decline is sharper, from 0.96 above [Formula: see text] = 35.96 g kg to 4.99 below [Formula: see text] (~-620%). Although salinity's significance in explaining SOC variability is minor (