Climate Change, Vegetation Belts and Vitality of Pubescent Oak and Aleppo Pine on the Istrian Peninsula, Croatia

This study analysed climate change in the eu-Mediterranean and sub-Mediterranean areas of the Istrian Peninsula, Croatia, and examined the influence of climatic conditions on crown defoliation in pubescent oak and Aleppo pine. Climate data from representative meteorological stations for the period 1980–2022 and crown defoliation data for 2000–2023 were analysed. Drought conditions were assessed using potential evapotranspiration, rainfall anomaly indices, and the number of dry months. The results indicated a significant increase in mean annual air temperature and potential evapotranspiration throughout the Istrian region, with temperatures rising by 0.8–1.2 °C compared to the reference period. Southern Istria experienced three dry months, characteristic of the steno-Mediterranean vegetation zone, indicating increasing aridity. The highest proportion of trees was recorded in the 26–60% defoliation class, including 54% of Aleppo pine and 59% of pubescent oak trees. Crown defoliation showed significant correlations with precipitation, rainfall anomaly index, and air temperature. Higher temperatures were associated with moderate defoliation levels, while lower minimum temperatures negatively affected severely defoliated Aleppo pine trees. No statistically significant differences in crown defoliation were found between pubescent oak and Aleppo pine.