Work

Extensive forest canopy discoloration during the 2024 heat-drought in southeastern Central Europe: The response of sessile oak (Quercus petraea) in Croatia was consistent with premature leaf senescence

Year: 2026

Type: article

Abstract: Extreme heat, drought, and pests impose growing stress on forests, causing canopy discoloration that is often difficult to attribute using remote sensing. In August 2024, large-scale premature leaf discoloration (PLD) occurred in forests of Southeastern Central Europe (SECE) associated with a prolonged heat-drought event. We analysed its spatial extent and species-specific occurrence using reflectance time-series from Terra/MODIS (2000–2026) and Harmonized Landsat and Sentinel-2 (2017–2025). The Green Red Vegetation Index (GRVI) was used to identify the timing of PLD. Red reflectance ( r red ) and NDVI, combined with tree-species distribution maps for Croatia, were used to analyse abiotic and biotic stress signals. An estimated 297–645 kha (1.7–2.5%) of SECE forests showed PLD in 2024. Species-specific analyses in Croatia (Slavonia) revealed that Quercus petraea was the most affected (69.4% in high-dominance stands), whereas Fagus sylvatica showed negligible PLD. In Q. robur, PLD was observed consistently since 2016 and associated primarily with the oak lace bug (OLB) infestation. Heat-drought PLD was characterized by rapid NDVI decline and sharp r red increase, whereas the OLB-consistent PLD showed slow NDVI decline and modest r red increase. Modelling results indicate that PLD proportion was positively associated with cumulative nighttime heat load and global radiation, rather than with maximum temperature. A strong increase in r red , a senescence-like NDVI decline, negligible PLD in F. sylvatica , and near-full recovery of Q. petraea suggest that the observed PLD was more consistent with the premature leaf senescence (PLS) hypothesis than with widespread acute leaf-tissue injury, but further research is needed.

Source: Agricultural and Forest Meteorology

DOI: 10.1016/j.agrformet.2026.111450

Authors: Anikó Kern, Hrvoje Marjanović

Institutions: Obuda University, Eötvös Loránd University, Croatian Forest Research Institute

Language: English

Topic: Remote Sensing in Agriculture

Subfield: Ecology

Field: Environmental Science

Domain: Physical Sciences

SDG: Life on land

Open Access status: hybrid

Estimated APC paid: $3,590