The age structure of Ulmus L. stands in the eastern regions of Ukraine

Abstract

The aim of the research was to determine the features of the age structure for natural and artificial elm stands depending on species, origin, and region. The proportion of the stand area of natural and artificial stands of each elm species by 10-year age classes was evaluated for the forest fund of the Donetsk, Kharkiv, and Sumy Regional Forest and Hunting Management Administrations (RFHMA). Four main forest-forming elm species are represented in the forest fund of the Donetsk and Kharkiv RFHMA (U. minor, U. laevis, U. glabra, and U. pumila). In the Sumy RFHMA, there are three forest-forming elm species: U. minor, U. laevis, and U. glabra. The maximum age of U. minor is 120, 117, and 91 years in the Donetsk, Kharkiv, and Sumy RFHMA, respectively. The mean and the maximum age of U. minor and U. glabra tends to decrease in the Donetsk – Kharkiv – Sumy RFHMA row. The proportion of U. laevis is larger in man-made plantations than in natural stands, however, in natural stands, it also increases in the Donetsk – Kharkiv – Sumy RFHMA row. U. glabra prevails in natural stands. U. pumila in the Donetsk RFHMA grows mainly in man-made plantations. A decrease in the area of newly formed U. minor stands in the Donetsk RFHMA occurred after the 1950s, and in the Kharkiv RFHMA after the 1960s in both artificial and natural stands. In the Sumy RFHMA, this also happened in the 1960s in man-made plantations. A decrease in the area of U. glabra natural and artificial stands occurred also after the 1960s. We suppose that an epiphytoty of the Dutch elm disease, well-known in Europe in the 1960s, could also be the cause of elm decline in the eastern part of Ukraine. The proportion of the stands’ area preserved up to a certain age, depends on particular elm species, region, and stand origin. However, in order to clarify the survival rate, it is necessary to consider the type of forest site conditions, the proportion of elms in the stand composition, and some other features that are to be analyzed in future research.