Response of Tree-Ring Oxygen Isotopes to Climate Variations in the Banarud Area in the West Part of the Alborz Mountains

Stable oxygen isotopes in tree rings (δ18O) serve as important proxies for climate change and offer unique advantages for climate reconstruction in arid and semi-arid regions. We established an annual δ18O chronology spanning 1964–2023 using Juniperus excelsa tree-ring samples collected from the Alborz Mountains in Iran. We analyzed relationships between δ18O and key climate variables: precipitation, temperature, Palmer Drought Severity Index (PDSI), vapor pressure (VP), and potential evapotranspiration (PET). Correlation analysis reveals that tree-ring δ18O is highly sensitive to hydroclimatic variations. Tree-ring cellulose δ18O shows significant negative correlations with annual total precipitation and spring PDSI, and significant positive correlations with spring temperature (particularly maximum temperature), April VP, and spring PET. The strongest correlation occurs with spring PET. These results indicate that δ18O responds strongly to the balance between springtime moisture supply (precipitation and soil moisture) and atmospheric evaporative demand (temperature, VP, and PET), reflecting an integrated signal of both regional moisture availability and energy input. The pronounced response of δ18O to spring evaporative conditions highlights its potential for capturing high-resolution changes in spring climatic conditions. Our δ18O series remained stable from the 1960s to the 1990s, but showed greater interannual variability after 2000, likely linked to regional warming and climate instability. A comparison with the δ18O variations from the eastern Alborz Mountains indicates that, despite some differences in magnitude, δ18O records from the western and eastern Alborz Mountains show broadly similar variability patterns. On a larger climatic scale, δ18O correlates significantly and positively with the Niño 3.4 index but shows no significant correlation with the Arctic Oscillation (AO) or the North Atlantic Oscillation (NAO). This suggests that ENSO-driven interannual variability in the tropical Pacific plays a key role in regulating regional hydroclimatic processes. This study confirms the strong potential of tree-ring oxygen isotopes from the Alborz Mountains for reconstructing hydroclimatic conditions and high-frequency climate variability.

• Publication year

  2025

• Venue

  Forests

• Publication date

  2025-07-28

• Fields of study

  Not labeled

• Identifiers
  DOI 10.3390/f16081238
• External record

  Open on Semantic Scholar

• Source metadata

  Semantic Scholar

• No claims are published for this paper.

• No concepts are published for this paper.

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