Land use conversion, climate change and soil organic carbon: Modeling a citrus garden chronosequence in Northern Iran

Abstract

After forest clearing and shift to high-production agriculture, land use conversion significantly impacts soil quality and reduces soil organic carbon (SOC) stocks. In Mazandaran province (Northern Iran), significant deforestation has occurred for many decades, and citrus orchards represent the major source of income for local farmers. Therefore, the RothC model was used to evaluate the changes in SOC stocks and the effects of climate change (CC) on SOC stocks after the conversion of a natural forest to citrus gardens (CG) of different ages, namely ≤10 years old (CG ≤ 10), 11–15 years old (CG15) and 16–20 years old (CG20). We also investigated two General Circulation Models (MPI ESM-LR and MIROC-ESM-CHEM) and two CO2 Representative Concentration Pathways (RCP4.5 and RCP8.5) on SOC stocks for a period of 30 years. Under CC conditions (2019–2048), SOC stocks increased in both emission scenarios in the natural forest (0.13–0.16 Mg C ha−1 yr−1) with the MPI ESM-LR model, but in citrus gardens, the increase was lower (0.10–0.11 Mg C ha−1 yr−1). Conversely, with the MIROC-ESM-CHEM model, SOC stocks decreased in both land covers. However, the decrease was higher in the natural forest (0.24 Mg C ha−1 yr−1) compared with the citrus gardens (0.11 Mg C ha−1 yr−1) under the high emission scenario. The study also allows identifying possible future strategies for better management of citrus gardens in this region from a climate change perspective.