Causes and trends in pathological damage to common ash

Intensive dieback of Fraxinus excelsior L. in the Forest-Steppe zone of Ukraine has led to a significant deterioration in the sanitary condition of ash stands and increased the risk of losing their ecosystem stability, making this issue particularly urgent amid the simultaneous influence of pathogens and the activation of a complex of stem-damaging insect species. This study aimed to analyse the ecological role of common ash in forest ecosystems, as well as to assess the sanitary condition and causes of ash stand decline, particularly the impact of Hymenoscyphus fraxineus and Agrilus planipennis . The study employed methods of analytical review, synthesis of previous research, critical comparison of results obtained by different authors, and logical-structural generalisation to identify key patterns in the development of pathological processes in ash stands. It was established that common ash supports intensive nutrient cycling due to litterfall with a high content of calcium and magnesium, and the rapid mineralisation of organic matter, which supports soil fertility and understorey development. According to the analysed studies, more than 950 associated species have been recorded, including 44 obligate and 62 highly specialised organisms, demonstrating the ash’s importance for biodiversity. The loss of ash reduces the rate of organic matter mineralisation and disrupts the nitrogen and carbon balances in the soil. Analysis of the sanitary condition in the Right-Bank Forest-Steppe of Ukraine showed that the most severely affected stands are located in the Cherkasy and Vinnytsia regions, where the area of dieback exceeds 600 ha. The main degradation factors include infections caused by Hymenoscyphus fraxineus , damage by Agrilus planipennis , bacterial diseases, and the combined influence of saprotrophic fungi. The results also indicate a strong relationship between the intensity of damage and tree age, stand density, and soil type, which enables the identification of zones at the greatest risk