Interannual variability of European beech spring phenology across elevation gradients derived from Sentinel-2 time series

Potočnik Buhvald, Ana (author), Oštir, Krištof (author), Skudnik, Mitja (author)

Spring 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.

• Language: English
• Keywords: fagus sylvatica, land surface phenology, red-edge vegetation indices, IRECI, mountainous forests, thermal forcing, in situ observations
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FGG - Faculty of Civil and Geodetic Engineering
• Publication status: Published
• Publication version: Version of Record
• Year: 2026
• Number of pages: 14 str.
• Numbering: Vol. 97, art. 103934
• PID: 20.500.12556/RUL-185218
• UDC: 551.506.8:581.54(497.4)
• ISSN on article: 1878-0512
• DOI: 10.1016/j.ecoinf.2026.103934
• COBISS.SI-ID: 286243843
• Publication date in RUL: 29.07.2026

Record is a part of a journal

• Title: Ecological informatics
• Publisher: Elsevier
• ISSN: 1878-0512
• COBISS.SI-ID: 62725635

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: fagus sylvatica, fenologija kopenskega površja, vegetacijski indeksi rdečega roba, IRECI, gorski gozdovi, temperaturni vpliv, opazovanja in situ