Structural comparative analysis of forest and steppe plant communities in the south of Kryvyi Rih region

Abstract

We made a comparative analysis of the floristic structure of 11 various-aged (30–50-year-old) forest and four steppe communities in the south of Kryvyi Rih region. We ascertained that the forest communities have low specific richness (2–90 species), whereas steppe ones contain from 167 to 251 species. The ten families leading in the species number are: Asteraceae, Poaceae, Rosaceae, Fabaceae, Lamiaceae, Caryophyllaceae, Boraginaceae, Apiaceae, Brassicaceae and Polygonaceae. Specific representation of the steppe communities depends on the geomorphologic formation, grazing pressure, soil cover composition; respective order of families differs slightly: Asteraceae, Poaceae, Fabaceae, Rosaceae, Scrophulariaceae, Lamiaceae, Caryophyllaceae, Brassicaceae, Apiaceae, Boraginaceae. The core of the geographical structure of forest vegetation is the species with a palaearctic type of range (30.3–54.5%), and in the steppe, species with the Black Sea area group (15.6–24.0%). The second and the third most numerous in forest groups are groups of species of transitional areas (3.6–23.3%) and holarctic species (7.0–17.2%). In the steppe communities, almost the same proportions are formed by the species of the palaearctic group and the plants of group of transitional areas (15.8–23.1% and 18.3–21.7% respectively). We revealed that in the forest and steppe communities the most numerous group in the spectra is the biomorph of hemicryptophytes (25.6–42.4% and 45.8–47.0% respectively). According to the structure of the above-ground shoots, identical proportions are formed by rosetteless and semi-rosetted species (38.3–60.5% and 37.2–56.7% respectively) in the forest communities, and semi-rosetted species (47.4–49.1%) in the steppe ones; as for the type of structure of underground shoots in forest communities, species without special underground formations (33.3–65.1%) and caudex formations (18.6–36.4%) prevail, and, in the steppe communities – caudex species do (39.1–47.9%); xeromesophytes (33.3–100%), and mesoxerophytes (32.9–40.6%) dominate in the hygrospectra of forest and steppe communities respectively; in heliospectra, there is the predominance of heliophytes (62.3–97.1% and 50.8–67.5% respectively); in trophoscopes, the mesotrophs are prevalent (57.1–98.4% and 47.0–52.1% respectively). The ecological and coenotic spectrum of forest communities is characterized by the domination of synanthropophants (36.3–58.6%), and in steppe ones – steppants (51.8–55.0%). We revealed the similarity of the floristic composition of forest and steppe communities (6.8–39.4%), and the largest index is noted for the plot with a strict nature reserve regime (19.4–39.4%). In forest communities, this value is 15.6–66.7%, and it varies in different-aged plantations of the same species. The analysis shows that there are significant differences in the floristic and biomorphological composition of forest and steppe communities; it confirms the concept of O.L. Belgard on the environment transforming function of artificial steppe forests, changing the biotic circulation, which is inherent in the steppes.