Ключові слова
Як цитувати
Анотація
Introduction
European ash (Fraxinus excelsior L.) is currently threatened across most of its distributional range by ash dieback caused by Hymenoscyphus fraxineus. In eastern Ukraine, the first appearance of ash decline symptoms was observed in 2010, and the H. fraxineus was detected in symptomatic shoots in 2012. The disease results in both a premature death of trees and stands and deterioration of wood quality. The pathogen spreads during the summer with spores that are formed on the infected leaves in the litter in winter and later are carried by the wind. Next summer these spores infect the leaves of healthy ash trees leading to leaf wilting, necrosis of shoots and stem. Our previous research showed that susceptibility of European ash to different pathogens as well as the severity of tree damage increase with a tree age. To predict the threat of ash damage, it was necessary to recognize the dependence of its incidence on other characteristics of the stands.
The aim of this work was to reveal the features of ash dieback distribution in the different forest site conditions, age, the relative density of stocking, site index, and ash proportion in the stand composition in the Left-Bank Forest-Steppe of Ukraine.
Materials and Methods
Inspection of ash stands was carried out in 2016–2019 at 52 permanent sample plots and 125 temporary sample plots in the State Forest Enterprises located in the Left-Bank Forest-Steppe, particularly in four forestries (Neskuchanske, Lytovske, Makivske, and Krasnianske forestries) of Trostianetske Forest Enterprise of Sumy Region (hereinafter referred to as Sumy Region) and in two forest enterprises of Kharkiv Region: Chuguyevo-Babchanske Forest Enterprise (Kochetokske fFrestry) and Skrypayivske Training and Experimental Forest Enterprise (Skrypayivske and Mokhnachanske forestries) (hereinafter referred to as Kharkiv Region).
Presence or absence of visual signs of ash dieback were registered, particularly necrotic spots on the bark of shoots, discoloration of wood and foliage, necrosis of foliage and stems, dieback of twigs and epicormic shoots. All inspected subcompartments with European ash (Fraxinus excelsior L.) as the main forest-forming species and subcompartments with the symptoms of ash dieback were grouped by the types of forest site conditions, age, the relative density of stocking, site index, and proportion of European ash in the stand composition.
The distribution of ash stands with the symptoms of ash dieback and without it was compared using the chi-square test (Atramentova & Utevskaya 2008) in MS Excel.
Results and Conclusions
The incidence of ash dieback in the forest-steppe part of Sumy and Kharkiv Regions was analyzed taking into account a type of forest site conditions, stand age, relative stocking density, site index class, and a proportion of European ash in the stand composition. Ash dieback is quite widespread in the inspected stands of the Left-Bank Forest-Steppe of Sumy and Kharkiv Regions. The spread of the disease is the same in natural and artificial stands. The disease was found more often in the fresh fertile forest site conditions. However, such forest site conditions are most spread and most favourable for European ash. The ash dieback incidence tend to grow with a stand aging uup to 80 years old which can be explained by a later development of stem and collar rots. Ash dieback incidence is the highest at 40–70 % of ash in the stand composition, at a relative density of stocking over 0.5 and in the stands of different site index classes.
10 Figs., 9 Refs.
Key words: forest site conditions, stand age, relative stocking density, site index class, ash proportion.