Species-specific coupling of transpiration and radial growth to climate in temperate forests of Korea

Tree growth and water use are fundamental indicators of forest ecosystem functioning and are expected to respond differently to ongoing climate change. We analysed continuous stem radial growth and sap flow data from long-term monitoring sites at Mt. Taehwa and the Gwangneung forest in Korea, focusing on Pinus koraiensis and Quercus spp. stands at Mt. Taehwa during the period 2013–2024. Stem diameter growth was measured using custom dendrobands. To identify both short-term and carry-over climatic controls, annual transpiration and radial growth were related to air temperature, photosynthetically active radiation (PAR), and precipitation using a multi-window framework that distinguished current-year from previous-year climate effects. For P. koraiensis, annual transpiration showed a strong positive relationship with early-summer precipitation, indicating a direct water-supply control on water use. In contrast, transpiration in the oak stand was only weakly related to precipitation. Despite these contrasting transpiration responses, stem radial growth of both pine and oak species exhibited pronounced sensitivity to antecedent-year climate, demonstrating substantial carry-over effects. These results reveal a temporal decoupling between transpiration and growth and highlight the importance of climate memory in regulating stem growth across temperate forest types, providing new insights into forest vulnerability under increasing hydroclimatic variability.