Interannual variability of European beech spring phenology across elevation gradients derived from Sentinel-2 time seriesPotočnik Buhvald, Ana (Avtor) Oštir, Krištof (Avtor) Skudnik, Mitja (Avtor) fagus sylvaticaland surface phenologyred-edge vegetation indicesIRECImountainous foreststhermal forcingin situ observationsSpring phenology of temperate deciduous forests is highly sensitive to interannual temperature variability, particularly in mountainous regions where strong elevational gradients create pronounced spatial differences in thermal forcing. In this study, we use dense Sentinel-2 time series to quantify start-of-season (SOS) dynamics of European beech across Slovenia between 2018 and 2021 and compare satellite-derived phenology with in situ observations from the Slovenian National Phenological Network. Satellite-derived SOS estimates showed moderate agreement with in situ phenological observations. Spring onset showed a clear elevational gradient, with SOS delayed by approximately 2.5–2.8 days per 100 m increase in elevation, consistent with temperature-related differences in spring thermal accumulation across the mountain landscape. Interannual variability was substantial, with a 16.9-day difference in national mean SOS between 2018 and 2021. Spatial patterns of phenological shifts reflected contrasting spring thermal conditions, suggesting a close association between SOS variability and April temperature during the 2018–2021 study period. These results highlight the short-term temperature-associated variability of European beech spring phenology and demonstrate the potential of high-resolution satellite time series to quantify canopy-level phenological patterns in topographically complex landscapes.20262026-07-29 07:42:35Članek v reviji185218sl