Abstract Stable carbon isotopes in Holocene soils provide key insights into past climate and ecosystems. This study presents high-resolution isotope analyses of pedogenic carbonates and organic carbon from modern loess-derived soils in northern Iran across a strong precipitation gradient (150–850 mm mean annual precipitation MAP). Eight soil profiles span five soil orders: Alfisols, Mollisols, Inceptisols, Aridisols, and Entisols. The mean δ 13 Cpc values show strong linear relationships with MAP (δ 13 Cpc = −0.0093 × MAP + 1.8878; R 2 = 0.98) and with the ratio of precipitation to potential evapotranspiration, P/PET (δ 13 Cpc = −8.6842 × P/PET + 1.608; R 2 = 0.99), indicating that δ 13 Cpc reliably reflects moisture availability during carbonate formation. Values range from −6.2‰ in wetter sites to −0.1‰ in dry areas, reflecting changes in soil respiration and CO₂ flux. δ 13 Coc values (−25.6‰ to −23.3‰) indicate dominant C₃ vegetation and exhibit a bimodal response to precipitation, increasing from arid to semiarid zones and decreasing in wetter forests. Oxygen isotopes in carbonate (δ 1 ⁸Opc = −7.9‰ to −6.6‰) show limited climate sensitivity, reflecting precipitation mainly from the Caspian Sea with minimal evaporative enrichment. Overall, δ 13 Cpc, δ 13 Coc, and δ 1 ⁸Opc provide robust proxies for soil moisture, vegetation structure, and water sources, supporting paleoenvironmental reconstruction in loess systems.
Khormali et al. (Tue,) studied this question.