image: Isoscapes illustrating the spatial distribution of tree-ring oxygen isotopes across Asia, generated using machine learning from 313 multi-year tree-ring records. The “sandwich” pattern features depleted values at high (>50°N) and low (<30°N) latitudes, and enriched values at mid-latitudes (30–50°N).
Credit: Modified from Huang et al., National Science Review, 2025
An international team, led by Professor Chenxi Xu from the Institute of Geology and Geophysics, Chinese Academy of Sciences, has generated the first continental-scale isoscapes of δ¹⁸OTR across Asia using 313 multi-year records. The study, published in National Science Review, used machine learning methods to generate a high-resolution map at 0.5° × 0.5° spatial resolution.
The isoscapes reveal a distinctive sandwich distribution pattern: depleted δ¹⁸OTR values at high latitudes (above 50°N) and low latitudes (below 30°N), with enriched values at mid-latitudes (30–50°N). This spatial pattern closely matches the distribution of precipitation oxygen isotopes (δ¹⁸OP) during the May–September growing season, indicating a strong connection between atmospheric moisture and tree-ring isotopic composition. The isoscapes also delineate a monsoon transition zone over the central Tibetan Plateau, consistent with independent δ¹⁸OP constraints and highlighting the sensitivity of isoscapes to monsoon dynamics.
To understand what controls this pattern, the team integrated observational data with three isotope-enabled climate models (IsoGSM, ECHAM5, and LMDZ4). Quantitative analyses further identify δ¹⁸OP as the primary driver of δ¹⁸OTR variability, while relative humidity plays a secondary role.
The researchers also investigated the relationship between δ¹⁸OTR and elevation. At the continental scale, no significant correlation was found (p > 0.05). However, a significant negative relationship (r = –0.69, p < 0.05) emerged specifically in the Indian Summer Monsoon region, with oxygen isotope values decreasing by 0.15‰ per 100 meters of elevation gain. This finding suggests that isotope-based reconstruction of past elevations is most reliable in regions with a dominant, single moisture source.
The findings provide a framework for understanding how atmospheric circulation and climate factors shape oxygen isotope patterns in tree rings across large geographic scales. The isoscapes act as a valuable tool for paleoclimate and paleoenvironmental reconstruction and tracing moisture sources. Beyond paleoclimate reconstruction, the newly developed δ¹⁸OTR isoscape provides an essential reference for wood provenance tracing. The map enables isotopic comparison between timber or wooden artifacts and their potential source regions, supporting efforts in sustainable forestry, heritage conservation, and the fight against illegal logging.
The Asian tree-ring oxygen isoscape dataset is openly available via Zenodo, providing a resource for researchers across climatology, ecology, hydrology, and environmental forensics. This work establishes a foundation for future global δ¹⁸OTR isoscape development and for integrating multiple environmental proxies to improve understanding of Earth’s water cycle and climate evolution.
About the Institute:
The Institute of Geology and Geophysics, Chinese Academy of Sciences, is dedicated to advancing the frontiers of Earth and planetary science, addressing national strategic needs in areas such as resource and energy security, habitable environments, and deep space exploration. It focuses on developing new theories in Earth and planetary sciences, creating key technologies and equipment for deep Earth exploration, and designing scientific payloads for deep space missions.
Journal
National Science Review
Method of Research
Data/statistical analysis