Site-Specific Functional Response of the Tibetan Plateau's Forests to Climate Change Over the Past 200 Years - A Tree-Ring Isotope Perspective.

O▬H coupling in Tibetan Plateau forests varies by moisture regime, with drought-linked decoupling at the moist site and persistent decoupling at the arid site over 200 years.

• Why it matters: Moisture-driven shifts in how trees balance autotrophic versus heterotrophic metabolism are hard to track, limiting understanding of forest resilience under climate change on the Tibetan Plateau.
• What they did: Across a moisture gradient, the study used 200-year tree-ring width and carbon isotope variation (δ13C) to assess water stress, and measured covariation between tree-ring cellulose δ18O and δ2H to quantify O▬H coupling.
• The result: Moist sites showed strong, stable O▬H coupling that weakened during recent droughts alongside reduced growth, while semi-arid and arid sites showed lower or persistent decoupling; combined with instrumental data, coupling strength depended on site-specific hydroclimatic baselines and can serve as an early-warning indicator of functional shifts.

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