The Populations and Habitat Preferences of Three Elm Species in Conditions Prevailing on Plains of Poland

From among the 35–40 elm species existing around the world, three are native to Europe: the wych elm (Ulmus glabra Huds.), the European white elm, (Ulmus laevis Pall.), and the field elm (Ulmus minor Mill.). The populations of these trees have been greatly reduced as a result of a decrease in the total area of riparian forests. Furthermore, for nearly 100 years, they have been destroyed by Dutch elm disease (DED). The main research problems of this study are: what are the habitat preferences of elms growing in a given area; and whether the occurrence of DED depends on the species of elm and the habitat in which it occurs. The results presented here are based on field studies and observations have been supplemented with data from forest inventories. All of the examined elms are definitely more abundant in habitats that are fertile or very fertile and moist, with a neutral or slightly alkaline soil pH. The preference for moist sites is the most evident in the case of U. laevis and the least evident in the case of U. glabra. A slight shift in habitat preferences of the field elm, compared to the white elm, towards less humid conditions was observed. The predominant species of elm in the studied area is currently U. laevis, which was rarely cultivated in forests in the past. In the examined area, the field elm population is clearly on the decline mainly due to the long-term presence of Dutch elm disease. U. glabra is the rarest species in the examined area and most often found on slopes. The current proportions of individual species should be maintained. This paper discusses factors, including ones not connected with DED, that may be responsible for the current state of populations of particular species of elm in forests of Central Europe.