Abstract
Common ash (Fraxinus excelsior L.) is an important part of the forest, shelterwood and ornamental stands. The health status of F. excelsior has recently deteriorated in many regions, due to climate change, anthropogenic stress, diseases and phytophagous insects. The effects of these factors are manifested in symptoms, the prevalence and severity of which depend on local conditions, in particular forest site conditions, stand composition, and structure. The aim of the research was to identify the forest site conditions and other stand characteristics most favourable for the prevalence and severity of symptoms of ash decline in Zhytomyr Polissya. The tasks were: to evaluate the common ash health condition, the symptoms of its decline, and their prevalence and severity in relation to forest category, forest site conditions, main forest forming tree species, ash origin, age, and relative stocking density. The majority of the ash stands surveyed were found to be weak. The health condition of F. excelsior deteriorates with age. It is worse in forest belts, in damp relatively fertile forest site conditions (С4), in the stands of vegetative origin, with a lower relative stocking density, and in the stands with Alnus glutinosa as the main forest forming species. Dry branches, epicormic shoots, collar rot, and ash bark beetles were the most common symptoms of ash weakness. The prevalence and severity of most of these symptoms were the highest in the forest shelter belts, in the damp relatively fertile forest site conditions (С4), in the stands of vegetative origin, with a lower relative density of stocking and older than 60 years. It is necessary to monitor the health status of F. excelsior in order to detect pathological processes and to select trees for selective sanitary felling in time. The severity of collar rot increased at the relative stocking density of 0.8. It is proposed to grow F. excelsior in mixed stands mainly with Quercus robur and to give preference to seed origin. It is necessary to monitor the health status of F. excelsior in order to detect pathological processes and to select trees for selective sanitary felling in time