Tree-ring δ¹⁸O as a robust proxy for hydroclimate in disturbance-prone terrain on the eastern Tibetan Plateau margin

Tree rings provide annually resolved and precisely dated climate information on past climate variability. However, in disturbance-prone areas, tree-ring width (TRW) can be strongly affected by stand dynamics and geomorphic disturbances, introducing non-climatic noise into chronologies and causing non-stationary climate–growth relationships. Here, we combined a newly developed ring-width index (RWI) with a tree-ring δ¹⁸O chronology from Pinus tabuliformis at Mt. Cuifeng, located along the western margin of the East Asian summer monsoon (EASM) on the eastern Tibetan Plateau margin, to evaluate the relative robustness of the two proxies in recording hydroclimate. Raw TRW measurements exhibit a prolonged juvenile effect and a pronounced growth release in the mid-20th century. In contrast, the tree-ring δ¹⁸O record is comparatively stable, showing neither a systematic juvenile trend nor a corresponding isotopic anomaly during the growth release period. Climate response analyses indicate that RWI responds negatively to temperature, primarily reflecting the limiting effect of temperature-induced growing-season moisture stress on radial growth. Tree-ring δ¹⁸O is more closely related to moisture-balance variables, including previous October precipitation, May–August vapor pressure deficit (VPD), and July–September scPDSI. This mid- to late-summer seasonality coincides with the period when the EASM rain belt prevails over the monsoon-margin region. Regional network comparisons further show weak inter-site coherence among RWI chronologies, likely reflecting site-specific disturbance histories, microenvironmental heterogeneity, and local growth limitations. Tree-ring δ¹⁸O chronologies maintain significant spatial synchrony across sites, even across different bioclimatic settings. Our study demonstrates that, compared with RWI, tree-ring δ¹⁸O provides a more physically interpretable and comparatively disturbance-resistant hydroclimate proxy, thereby improving hydroclimate reconstruction reliability in disturbance-affected landscapes.