Common ash (Fraxinus excelsior L.) in Ukrainian forests and its successful natural regeneration

Abstract The natural distribution area of common ash (Fraxinus excelsior L.) in the forests of Europe and Ukraine has been determined through the analysis of scientific works of Ukrainian and foreign researchers. According to the reference materials on the current state of Ukrainian forests (25 administrative regions), it is established that ash forests cover an area of about 150,000 ha or 2.4% of the total area of the country’s forests. Among them, common ash stands account for almost 87% or 130,000 ha; the rest are stands of introduced ash species, namely F. pennsylvanica Marsh., F. americana L., and F. lanceolata Borkh. The average age of ash stands is 59 years. Only 6.4% (8,300 ha) of the total area of ash forests is covered by pure ash stands, and the remaining area (93.6% or 121,700 ha) are mixed ones. It is revealed that the optimal natural and climatic conditions for the emergence, preservation and successful growth of natural regeneration of ash trees are fresh and moist fertile sites (rich in minerals) with well-drained soils, the light of at least 5–6% of that on an open space, and without abundant live ground cover. The highest number of seed regeneration of ash, about 7,000–8,000 stems ha−1 on average, was found under the canopy of mixed (ash share in the composition was 10 to 20% by stock) old (over 100 years old) stands with a relative density of stocking of 0.7–0.8. Promoting the natural seed regeneration of ash trees can be an effective way of increasing the sustainability of such stands and will ensure their preservation in the forests of Ukraine and in deciduous forests of Europe as a whole.