Potential and realized ecological niches of herb and shrub layer in forest ecosystems of the north-eastern Ukraine

Abstract

The species composition of herb and shrub layer of the major forest ecosystems of the north-eastern Ukraine has been analyzed at the level of vegetation classes, and individual ecological optimum of the main species of herbs and shrubs has been determined in order to predict the dynamics of their populations in the region. Literature data and results of our own studies for the period of 2000–2010 have shown that in accordance with the ecofloristic classification in the region, 6 classes of forest vegetation can be distinguished, such as: Querceto-Fagetea Br.-Bl. (1937), Vaccinio-Piceetea Br.-Bl. (1939), Pulsatillo-Pinetea sylvestris Oberdorfer (1992), Quercetea robori-petreae Br.-Bl. et. Tx. (1963), Salicetea purpureae Moor (1958), Alnetea glutinosae Br. Bl. ex Tx. (1943). The analysis of the general monographs on ecofloristic classification made in the north-eastern Ukraine (Klika, 1955; Matuszkiewicz, 2001; Shelyah-Sosonko, 2002; Grygora, 2005; Solomakha, 2008; Goncharenko, 2009, 2010; Rogova et al., 2005, etc.), provided an opportunity to review the composition of the characteristic species for the six classes of vegetation, registered in the region. Thereby, species, that hardly ever occur in the region or are very rare, have been excluded from the list of characteristic species. Plant species, peculiar to forest communities of the north-eastern Ukraine, have been added. Woody plants and shrubs have been excluded from the analysis. For each species of the three central classes its individual ecological optimum has been estimated considering six factors: 1 – light availability, 2 – temperature, 3 – continentality, 4 – soil moisture, 5 – soil acidity, 6 – soil fertility. The point scale of Ellenberg (Ellenberg, 1952, 1996) with 12 points for soil moisture and 9 points for other environmental regimes has been taken as a basis. Due to the fact that the scale of Ellenberg fails to include all these species, and has a lot of gaps in the assessment of individual regimes, it has been supplemented by the point scale of Landolt (Landolt, 1977), in which the number of species is greater and the assessment of their optimum is more complete. Considering that that in the scale of Landolt all environmental factors are divided into 5 points, transformation of points into 12- or 9-integrated assessment of environmental regimes has been made. The indicated pattern of wide ecological amplitude in characteristic species of higher syntaxonomic units in forest vegetation is useful adaptive trait from the phytocoenogenesis point of view. If there is any change in the general soil-climatic conditions, forest phytocoenoses retain their integrity due to the change in their great number and even the floristic composition in the lower tiers. Grouping of classes Querceto-Fagetea Br.-Bl. (1937), Vaccinio-Piceetea Br.-Bl. (1939) and Pulsatillo-Pinetea Sylvestris Oberdorfer (1992) play the leading role in the formation of forest ecosystems in the north- eastern Ukraine. Plant species, peculiar to these classes and being part of herb and shrub layer, provide wide ecological amplitudes, covering at least 3–5-point scales of the main environmental factors. Global warming may result in significant changes in the composition and structure of plant populations that form herb and shrub layer of forest phytocenoses of vegetation classes, peculiar to the north-eastern Ukraine.