Modeling the impact of climate change on soil organic carbon pools in the semi-arid climate of Mashhad using the RothC model

Document Type : Research Paper

Authors

1 PhD student, Dept. of Soil Science, Faculty of Agriculture, University of Zanjan, Zanjan, Iran.

2 Associate professor, Dept. of soil Science, Faculty of Agriculture, University of Zanjan, Zanjan, Iran

3 Associate Professor, Dept. of Soil and Water Research, Khorasan Razavi Agricultural and Natural Resources Research Center, AREEO, Mashhad, Iran

4 Assistant Professor, Dept. of Range and Watershed Management, Faculty of Natural Resources, University of Kurdistan, Sanandaj, Iran

10.22059/ijswr.2022.346264.669327

Abstract

Soil organic carbon is key to determining soil quality, health, and fertility. Due to the complexity of the structure and relationships of soil organic carbon pools, the use of models is beneficial in identifying the reaction of these pools to the change in ecosystem conditions. So, by using the RothC model, the effect of global warming and climate change on the amount of soil organic carbon reservoir of the agricultural ecosystem of southeastern of Mashhad was investigated. Therefore, the model was calibrated and validated using data measured in 2020 and available long-term data. Comparing the measured values of soil organic carbon and the simulated values by the model, the coefficient of determination (R2) was 0.89. Root means square error (RMSE): 3.45, mean difference (MD): 1.84, mean absolute error (MAE): 2.79, and model efficiency (EF) was 0.73, demonstrating the validity and suitability of the model. The modeling of the future climate changes of Mashhad showed that as a result of the decrease in rainfall and increase in temperature and evaporation, the amount of total soil organic carbon (TOC) would decrease by 1.13% compared to the current conditions. Considering the decomposition rate constant of the model's four active carbon pools, humus exhibited the slowest decomposition rate of 0.96%. At the same time, decomposable plant materials (DPM), resistant plant materials (RPM), and microbial biomass (BIO) were decreased by 1.18%, 2.21%, and 2.10%, respectively, compared to the current climate condition. Moreover, with time, the decomposition rate decreased due to the decay of active organic matter pools that are easily decomposed.

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