The comparative ecologo-phytocoenotical positions of the two feather-grass species (Stipa pennata L. and S. tirsa Stev.) in the plant communities of Yamskaya Steppe (Belgorod region)

There is a general phytocoenotic question — why the species similar taxonomically and ecologically can co-exist within a plant community? The paper deals with two of such species — Stipa pennata L. and S. tirsa Stev., that previously were considered by plant taxonomists as one species. They are reputed to be the most mesophytic feather-grasses, although there are a lot of contradictory opinions about their physiology and ecology. In 1920s and 30s two well-known Russian geobotanists B. Keller and V. Aljekhin conflicted on the problem. In our case both species co-exist in the steppe communities of the protected territory (zapovednik “Belogorie”). The phytocoenotical role of feather-grassesvaries in the different ecotopes. The phytocoenotical roles S. pennata and S. tirsa are very similar in the plant communities growing on the cold slopes. As for the warm sites, the participation of S. pennata in the communities is the same, whereas a presence of S. tirsa is considerably decreased. Each feather-grass de­monstrates a high correlation with specific grass species of communities. The obtained results show the clear phytocoenotic distinctions between two species.