Soil organic carbon response to interannual precipitation and potential evapotranspiration variability

Soil organic carbon (SOC) has a major impact on soil quality, and increasing SOC is of growing interest as a climate change mitigation strategy. However, previous work has shown that changes in SOC may vary with short-term climate cycles. This study aimed to investigate the relationship between precipitation, potential evapotranspiration (PET) and SOC at a greater spatial and temporal extent than previously done in Saskatchewan, Canada. Using data from the Prairie Soil Carbon Balance project, change in SOC was assessed as a function of mean growing season precipitation (May-August) and PET using generalized additive models. For change in SOC content and stock, rates of SOC change decreased with increased total precipitation and increased with increased PET. These trends reflect differences in the response of both plant growth (C inputs) and decomposition rates (C outputs) in different soil-climate conditions. These results confirmed that SOC can be expected to fluctuate with short-term climate variation. Hence, such relationships must be considered when assessing SOC changes due to management or estimating future SOC under a changing climate.