Recent warming and increasing CO₂ stimulate growth of dominant trees under no water limitation in South Korea.

This article focuses on the long-term physiological and growth responses of Quercus mongolica, a dominant cool-temperate oak species in East Asia, to rising temperatures and atmospheric CO₂ concentrations over the past century in South Korea’s Hallasan National Park. Using tree-ring width and stable isotope (δ¹³C and δ¹⁸O) analyses from 1924 to 2017, the study found that basal area increment, intercellular CO₂ concentration, and intrinsic water-use efficiency (iWUE) significantly increased overall, with variable trends across four distinct periods identified by change-point analysis. Notably, δ¹⁸O values remained stable, indicating no major hydrological changes in this precipitation-rich region. The recent two decades showed accelerated growth linked to higher spring–summer temperatures and CO₂ levels, alongside physiological indications of increased photosynthetic rates without water limitation, suggesting that Q. mongolica may currently benefit from recent climate changes, contrasting with declines reported in other temperate forests. These findings provide important insights for projecting forest dynamics and carbon sequestration under ongoing climate change in East Asia.