The objectives of this paper are the reviewing nemoral herb spruce forests of European Russia (ER), elaborating diagnostic species combination, revealing species diversity, discussing syntaxonomical position, and validation of nemoral herb spruce forest syntaxa.
The study concern 62 coenofloras (published and unpublished data from 11 regions of ER) and 448 relevés. The initial diagnosis of the association (Korotkov, Morozova, 1986; Zaugolnova, Morozova, 2004), originally based on local and incomplete materials, was refined, as a result of the generalization of a vast literature and factual data.
All nemoral herb spruce forests of ER belong to ass. Rhodobryo rosei–Piceetum abietis Korotkov 1986 (RP) with three subassociations: RP typicum, RP abietetosum sibiricae and RP caricetosum pilosae. The issues of syntaxonomic assignment of the association to the higher units are discussed. The position of association within the class Carpino-Fagetea, order Carpinetalia and alliance Querco-Tilion was justified by predominance of nemoral species in lower layers of communities. Diagnostic species of association (Picea abies (upper layer), Athyrium filix-femina, Circaea alpina, Daphne mezereum, Dryopteris expansa, Gymnocarpium dryopteris, Mycelis muralis, Oxalis acetosella, Phegopteris connectilis, Pyrola rotundifolia, Stellaria nemorum; Cirriphyllum piliferum, Plagiochila porelloides, Plagiomnium affine, P. medium, Rhodobryum roseum, Sciuro-hypnum starkei, S. curtum) are identified by fidelity index (Chytrý et al., 2002) and largely coincide with species of suballiance Tilio-Piceenion (Morozova, 2016). Alliance of Eastern European oak and lime tree forests Querco-Tilion is divided into two suballiances including proper deciduous forests (Querco-Tilienion) and spruce forests with nemoral herb and moss layers (Tilio-Piceenion), reflecting the zonal features of deciduous-coniferous forests in ER.
The specific traits of the association communities are the species polydominance and total predominance of nemoral species in the lower layers. Thus, nemoral species can be considered as a collective dominant, with a cover approximately equal to or exceeding that of Oxalis acetosella (Vasilevich, Bibikova, 2004). Dominant species in the herb-subshrub layer vary not only due to the local conditions, but also to the age of forest stands. O. acetosella, as well as Aegopodium podagraria, Carex pilosa, Galeobdolon luteum, Galium odoratum, Mercurialis perennis, Pulmonaria obscura, Stellaria holostea, and some fern species can predominate.
For subassociation, an ecological characteristics estimated by Ellenberg indicator scales (Ellenberg et al., 1991) are given. The floristic originality of syntaxa and the role of environmental factors are demonstrated by the method of nonlinear multidimensional scaling (NMDS).
Differentiation of the internal structure of the association at the lower hierarchy levels is difficult, since these forests are a very polymorphic group regarding the dominating species. The predominance of one or combination of several species is related to specific environments and can be identified at the level of the variants, which is reflected in development of regional classifications (Semenishchenkov, Kuzmenko, 2011; Morozova, Tikhonova, 2012; Semenishchenkov, 2012).
The area of eastern European nemoral herb spruce forests covers the territory from the east of the Baltic countries to the Volga river. Communities of association represent a zonal type of vegetation in the broad-leaved coniferous subzone and southern half of the southern taiga, but are extrazonal both in the north and south of their distribution. These forests occur on moraine loamy plains: in the southern taiga — mainly on the tops and slopes of hills, while in the broad-leaved coniferous subzone — on well drained plains and gentle slopes. Subassociations are differentiated by their geographical location: RP typicum represents west and central nemoral herb spruce forests, RP abietetosum occurs in the north-east of association range and RP caricetosum — in the south. For the most distinctive subassociation RP abietetosum character are the presence of Abies sibirica, hydrophylous and some species of Siberian tall herbs, and a smaller proportion of nemoral species.
The number of species in the coenofloras is not being changed on the latitudinal gradient, but the species richness of the communities, as well as the cover of the lower layers, decrease southwards. Perhaps this is due to the increased presence of hazel, which creates a pronounced level of the undergrowth in the RP caricetosum.
The floristic comparison and proposed concept of the nemoral herb spruce forests syntaxonomy make the regional syntaxonomic units comparable in volume and allow to adequately outline the modern range of forests of this type in ER.
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