Steppificated oak forests — the unique relic natural complexes of the Eastern Europe remained in Central Russia by small fragments. These forests are important elements of forest-steppe natural complexes and the reserves of rare plant species. In the European scientific literature the questions of their syntaxonomy, features of structure and dynamics are discussed (Mucina at al., 1993; Chytrý, 1997; Chytrý, Horak, 1997; Roleček, 2005, 2007; Kevey, 2008; etc.). The data on phytocoenotic diversity of such forests in Central Russia were obtained only recently but they are fragmented and insufficient.
According to the Braun-Blanquet approach these forests belong to the subcontinental forest-steppe alliance Aceri tatarici–Quercion Zólyomi 1957. Such forests are described within the areas of distribution of two important edificator species — Acer tataricum and A.campestre which the northeast areal border generally corresponds to the northeast border of the forest-steppe zone.
On the basis of geobotanical data collected by the authors on the Middle-Russian Upland (Belgorod, Kursk, Tula regions) the 4 new associations within the alliance Aceri tatarici–Quercion Zólyomi 1957 are described. Floristic differentiation of new syntaxa from the Central-European syntaxa is demonstrated by the DCA-ordination. Authors propose an original combination of the diagnostic species for this alliance, for the area studied.
Taking into account the floristic specificity of the forests of the region, we suggest uniting of the established associations into the new suballiance Crataego curvisepalae–Quercenion roboris. This alliance represents the East European mesoxerophyte broad-leaved (with Quercus robur) forests of forest-steppe zone of the Middle Russian subprovince of the East European forest-steppe province. The diagnostic species of the suballiance are following: Quercus robur, Acer platanoides, Chamaecytisus ruthenicus, Crataegus curvisepala, Frangula alnus, Melampyrum nemorosum, Sorbus aucuparia, Tilia cordata, Viburnum opulus. The suballiance is diagnosed by absence of thermophilous ous Quercus species, in particular, Q.petraea, Q.pubescens, Q.cerris, etc., their hybrid forms, and also some Central European and Sub-Mediterranean trees and shrubs: Acer pseudoplatanus, Carpinus betulus, Crataegus laevigata, C.monogyna, Cornus mas, Fagus sylvatica, Ligustrum vulgare, Sorbus aria, S.tomentosa, Tilia argentea, T.plathyphyllos, Viburnum lantana, Ulmus minor.
Results of the research spread our knowledge on distribution of the steppificatedbroad-leaved forests in the Central Russia. and geography of the alliance Aceri tatarici–Quercion in Eastern Europe.
THE PLACE OF QUERCUS ROBUR L. IN THE DYNAMICAL PROCESSES IN THE OAK FORESTS OF FOREST-STEPPE ZONE
