THE IMPACT OF PEDOCLIMATE ON SOIL SUBGROUP DEVELOPMENT IN A SEMI-ARID REGION OF IRAN

Understanding the relationship between climate and soil even on low levels of categories i.e., subgroups become increasingly vital. Pedoclimate was defined as a microclimate within the soil that can be identified by determining soil moisture and temperature regimes. This study focuses on evaluating soil subgroup development under different pedoclimate conditions across a semi-arid region of Iran. Based on the Java Newhall simulation model and climatic data from 52 meteorological stations over 30 years (1992-2022), the pedoclimate class was modeled. Using data from 670 soil profiles across the East Azerbaijan Province of Iran, the profile development index (PDI) was determined. Subsequently, the soils were classified into 12 subgroups. To create the final soil maps, a geopedological approach utilizing a weighted overlay technique was implemented, considering the influences of geology, topography, and land use. According to the Java Newhall simulation model, five distinct pedoclimatic zones were identified as follows: Mesic-Dry Xeric (46.58 %), followed by Thermic-Weak Aridic (23.97 %), Mesic-Typic Xeric (23.94 %), Thermic-Typic Aridic (5.37 %), and Frigid-Typic Xeric (0.14 %). The soil orders ranked by area extent are: Inceptisols (43.36 %) > Entisols (32.29 %) > Aridisols (21.31 %) > Mollisols (1.46 %). It was found that Entisols were under all pedoclimate classes while Inceptisols were identified only under the Xeric moisture regime. Based on the PDI values (on average), Typic Calcixerolls and Lithic Xerorthents respectively show the highest and the lowest development levels (29.6 and 6.7). Further visualization revealed that all Typic Calcixerolls were overlaid under the Mesic-Typic Xeric class. Moreover, there were no subgroups of Mollisols in the Aridic and Thermic classes. Interestingly, Xeric Haplocambids showed a similar development with Typic Haploxerepts. The study establishes the importance of pedoclimates in soil classification and development influenced by climate. Its findings enhance soil resource management and support new hypotheses and insights in various soil science fields.