Phytocoenotical behaviour of nemoral and boreal-nemoral plant species in taiga zone communities

Phytocoenotic behaviour of 14 nemoral or boreal-nemoral vascular plant species is analyzed in the middle- and southern-taiga subzones in comparison with that in the broadleaved-forest zone, based upon the set of 1669 relevés made in European Russia in 1996–2018. The nemoral species are mainly represented by shadow mesoeutrophic plants from the “corteges” of Tilia cordata s. l. and Fagus sylvatica. The more light-demanding plants from the Quercus robur “cortege”, either mesotrophic, or mesoeutrophic, more often demonstrate the boreal-nemoral type of zonal distribution. In the boreal-forest zone, linden and beech companions are typical for the southern-boreal nemoral-herb / sorrel spruce (Picea abies s. l.) forests on placors as well as the valley / riparian tall-herb forests, including the middle-boreal ones. The oak companions also inhabit grass-feathermoss pine (Pinus sylvestris) forests, besides the spruce forest types mentioned. Species from all the named “corteges” are also common in the small-leaved forests. The Betula companions which grow together with the nemoral plants in boreal forests could also be subdivided into the two florogenetical groups, namely a) the boreal, originally subalpine plants and b) the boreal-nemoral ones, originally oak companions. Species from the latter group often become widespread and dominant in the small-leaved forests; a good example is provided by Aegopodium podagraria. The rank correlation (Spearman rS) analysis shows the projective cover increase is connected with either the growing season warmth supply, or the climate oceanicity for both nemoral and boreal-nemoral species. These effects are most sound in the placor community sequence from broadleaved forests to sorrel and then bilberry-feathermoss spruce ones but weakened in the tall-herb forests on rich soil and completely levelled in the aspen (Populus tremula) forests. Carbonate bedrock outcrops contribute to nemoral species survival in the areas they inhabited during the climatically favourable epochs; they also favoured the migration of these species during the interglacials. Individualization of coenotic patterns of nemoral species at their distribution limits does not contradict to joint occurrence of such plants in relict / extrazonal locations.