Электронный атлас "Биоразнообразие животного и растительного мира Сибири"

Notes on syntaxonomy and nomenclatura

Brachypodio-Betuletea

Classes: Brachypodio-Betuletea

Notes on syntaxonomy and nomenclatura: Denisova (in ILJINA et al., 1988) described the alliance Roso majalis-Betulion pedulae (in the Querco-Fagetea class system) of flood-plain forests of the Irtysh river (West Siberian Lowland). Later, this alliance was attributed to the Brachypodio-Betuletea by TARAN (1993) despite the absence of distinct features of this class and order. These are birch (Betula pendula, B. pubescens) and pine (Pinus sylvestris) forests with poor floristic composition combining a few features of the classes Querco-Fagetea, (Alno-Padion Knapp 1942), Salicetea purpurea Moor 1958 and Brachypodio-Betuletea (Calamagrostio epigei-Betuletalia pendulae). At present, the syntaxonomical position of the alliance is unclear and additional data are required.

Notes on diagnostic species group: The characteristic herbaceous species of the class are North Asian ones: Pleurospermum uralense, Serratula coronata, Agrimonia pilosa, Lilium pilosiusculum. The main parts of the geographical ranges and ecological amplitudes of these species coincide with those of the class. Differential species for the class are Brachypodium pinnatum, Calamagrostis arundinacea, Vicia sepium, Angelica sylvestris and Pulmonaria mollis. These are moderately thermophilous species with a range of the European-Siberian type, the extent of which exceeds that of the class. In Europe, they occur in various forest and nonforest communities. But in the continental climate of South Siberia, a change of ecological peculiarities of the species is observed. As a result, in the eastern part of the range, they have a high degree of fidelity only to the communities of amphi-Atlantic hemiboreal forests. This group of European-Siberian differential species is thus of great diagnostic importance from a geographical point of view and the Siberian parts of the ranges of these species coincide with the distribution of the class because of the coincidence in macroclimatic conditions. Differential species for the class also are Rubus saxatilis, Hieracium umbellatum and Iris ruthenica. The first two have Eurasian and Holarctic ranges and occur in the different types of communities there, but in the territory of West and Middle Siberia they grow predominantly in the communities of mesophilous grass forests. The North Asian species Iris ruthenica has its phytocoenotic optimum in the mesophilous variants of steppes but it is nevertheless found regularly in the forests of the Brachypodio-Betuletea, and here it is of great diagnostic importance. The local characteristic species of the class is a North Asian one - Cimicifuga foetida which is of high fidelity in all its range. The best overall diagnosis of the class Brachypodio-Betuletea results from the analysis of the presence and phytosociological role of diagnostic species of both the class and those of subordinated orders. The communities of the Brachypodio-Betuletea show similarities in their floristic composition with East European and East Ural communities of the class Querco-Fagetea, because of the significant phytocoenotic role of European-Siberian and Eurasian species. In some Siberian amphi-Atlantic forests, three characteristic species of this class, Lathyrus vernus, Viola mirabilis, Melica nutans, are regularly found. Such species as Viburnum opulus and Epipactis helleborine are rare. Most of them have disjunct relic ranges in Siberia, which are much less than that of the class Brachypodio-Betuletea itself. We consider these species as regional characteristic species of the class Querco-Fagetea only in the territory of Europe in oceanic and suboceanic climates. Most of characteristic species of the Querco-Fagetea, especially the broad-leaved woody ones, have the eastern borders of their range at the South Urals and are absent from the territory of North Asia. In the Southern Urals, at the geographical border between these classes, there is a problem of deciding whether to ascribe some forest communities to the classes Querco-Fagetea or Brachypodio-Betuletea. The broad-leaved forests of the alliance Lathyro-Quercion Solomeshch et al. 1989 which have a contribution from numerous Siberian species in the herb layer occur there. In the same region, pine-birch forests of the Brachypodio pinnati-Betuletea with a weak participation of some Querco-Fagetea diagnostic grass species, are found in the drier sites. In this case, one of the effective criteria for separation of these classes is the significant phytosociological role of broad-leaved tree species and nemoral shrubs. The absence of diagnostic species of the class Vaccinio-Piceetea is characteristic of the majority of communities in the Brachypodio-Betuletea. The phytosociological role of some these species (Vaccinium vitis-idaea, V. myrtillus, Trientalis europaea, Orthilia secunda, Pleurozium schreberi, Hylocomium splendens, Ptilium crista-castrensis) occurs only in transitional communities as a result of increasing habitat humidity and cold. It is observed in a transitional zonal strip between hemiboreal and real boreal (taiga) forests.Furthermore, an intensification of the role of taiga species is evident in the hemiboreal forests which grow in the cold and humid depressions of the oligotrophic river terraces in the forest-steppe zone. In the arid continental climate of intermountain hollows of the Altai and Sayani, there are a series of communities transitional to the class Rhytidio-Laricetea sibiricae. In these forests, the role of xerophilous and cryo-xerophilous species such as Aster alpinus, Carex pediformis, Festuca ovina, Galium verum, Thalictrum foetidum, Veronica incana, Rhytidium rugosum and Abietinella abietina increases. Meadow species of the class Molinio-Arrhenatheretea are also a constant phytosociological element in the Brachypodio-Betuletea communities. The prominent role of these species in hemiboreal forests is caused by the influence of natural ecological factors like the temperate warm and humid climate, high soil fertility and the open tree layer as well as of anthropogenic factors such as grazing and cutting.

Nomenclatural type of the class: Carici macrourae-Pinetalia sylvestris Ermakov et al. 1991

Николай Ермаков

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