Pušpure, I., Matisons, R., Laiviņš, M, Gaitnieks, T. and Jansons, J. 2017. Natural Regeneration of Common Ash in Young Stands in Latvia. Baltic Forestry 23(1): 209-217.

   Due to the dieback caused by ascomycete Hymenoscyphus fraxineus, common ash (Fraxinus excelsior L.) regeneration currently occurs only naturally and is crucial for existence of the species. Hence, in this study, we assessed the success of the nat-ural regeneration and health condition of common ash in 90 diverse young stands. Additionally, the age structure of ash advance growth (saplings and seedlings) was characterized in four plots, initially dominated by ash. Ash was abundant in the advance growth in the studied plots with the mean density of 4185 ± 401 trees ha-1. Ash advance growth density and health condition de-creased with increasing height and age. From the 7533 accounted regeneration ashes, 75% were considered as healthy, 15% dam-aged and 10% were already dead. Ash regeneration density was the highest and the degree of H. fraxineus damage was the lowest in young stands on drained mineral soils. The best ash health condition was found in the densest stands with increased number of advance growth and undergrowth individuals. The highest ash mortality (ca 20%) was found in pure young stands. In the young stands, which were previously formed by ash, regeneration density was relatively low (4319 ± 592 trees ha-1), but the mortality intermediate (ca. 10% of all trees). In contrast, in the stands dominated by black alder and birch, the density of ash advance growth was higher – 7300 ± 6300 and 6933 ± 2711 trees ha-1, respectively, but the number of dead ash was lower (ca. 5%). Ash appeared more susceptible to the disease in the dense and unmanaged stands, as the health condition of ash regeneration was pos-itively related to the number of tendings. A significant correlations between diameter, age and height of ash was observed, yet the analysis of the dimension showed, that the ash regeneration after harvesting and/or dieback has been occurring at different rates.

Keywords: Fraxinus excelsior; advance growth; establishment; young stand; ash dieback; natural succession; hemiboreal forest zone.