Assessment of the potential shifts in the phenological development of representative spring plant species in Slovenia until the end of the 21st century using a model-based approach

To assess the changes in the spring phenology in the future with particular emphasis on the elevation dependence of phenophase onset, a climate-driven phenological model was developed based on the spring indices methodology. Our study investigates both current and projected changes in the timing of flowering onset for common hazel (Corylus avellana), dandelion (Taraxacum officinale), and common lilac (Syringa vulgaris). We compiled comprehensive climate data and phenological records from 46 phenological stations of the National Phenological Network of the Slovenian Environment Agency for the period 1971–2020. In addition, we used climate projection data for the 21st century under two climate scenarios to evaluate potential future shifts in the onset of the selected phenophases. Specifically, we examined whether the agreement between model predictions and observed records varies with elevation during the reference period (1981–2010) and whether this relationship changes across three future climate periods: 2011–2040, 2041–2070, and 2071–2100. Model results indicate that spring phenophases are expected to occur earlier in Slovenia by the end of the 21st century, consistent with the projected increase in air temperatures. Moreover, the advancement in spring phenology will be more pronounced at higher elevations.