Modeling Soil Organic Carbon Changes under Alternative Climatic Scenarios and Soil Properties Using DNDC Model at a Semi-Arid Mediterranean Environment

Soil organic carbon (SOC) is one of the central issues in dealing with soil fertility as well
as environmental and food safety. Due to the lack of relevant data sources and methodologies,
analyzing SOC dynamics has been a challenge in Morocco. During the last two decades, processbased
models have been adopted as alternative and powerful tools for modeling SOC dynamics;
whereas, information and knowledge on the most sensitive model inputs under different climate,
and soil conditions are still very limited. For this purpose, a sensitivity analysis was conducted
in the present work, using the DeNitrification-DeComposition (DNDC) model based on the data
collected at a semi-arid region (Merchouch station, Morocco). The objective is to identify the most
influential factors affecting the DNDC-modeled SOC dynamics in a semi-arid region across different
climatic and soil conditions. The results of sensitivity analysis highlighted air temperature as the main
determinant of SOC. A decrease in air temperature of 4 C results in an almost 161 kg C ha?1 yr?1
increase in C sequestration rate. Initial SOC was also confirmed to be one of the most sensitive
parameters for SOC. There was a 96 kg C ha?1 yr?1 increase in C sequestration rate under low initial
SOC (0.005 kg C ha?1). In the DNDC, air temperature in climatic factors and initial SOC in variable
soil properties had the largest impacts on SOC accumulation in Merchouch station. We can conclude
that the sensitivity analysis conducted in this study within the DNDC can contribute to provide a
scientific evidence of uncertainties of the selected inputs variables who can lead to uncertainties
on the SOC in the study site. The information in this paper can be helpful for scientists and policy
makers, who are dealing with regions of similar environmental conditions as Merchouch Station, by
identifying alternative scenarios of soil carbon sequestration.