Ecological and coenotic positions of Maianthemum bifolium (L.) F.W. Schmidt and Linnaea borealis L. within their northern range periphery

The research was aimed at detection of ecological and coenotic distribution regularities of Maianthemum bifolium (L.) F.W. Schmidt and Linnaea borealis L. within the northern taiga of European Russia in connection with changing natural conditions along the longitudinal gradient. The relevance of the study is due to insufficient contemporary knowledge about range structure for typical taiga species from the standpoint of ecological and coenotic connections. The study suggests that the species ecological amplitudes in different parts of the range differ due to changes in natural and biogeocoenotic conditions, which, in turn, will be reflected in the cenotic fidelity of the species and in the range structure. We analyzed ecological and coenotic positions of the plant species based on their constancy indexes, ecological amplitudes and connections with different types of forest communities. We processed more than 1600 geobotanical releves collected from various scientific publications and 45 authors' releves. These data were analyzed within the framework of six regions corresponding to the provinces of physical and geographical divisioning of the European northern taiga territory (See Table 1). The size of description samples is shown in Figure 1. The ecological amplitudes of the species were calculated on the basis of LG Ramensky's ecological scales; the mean values of moisture and nutrient status scales, standard deviation and confidence intervals for p<0.05 were calculated. For calculations, we used more than 150 geobotanical releves from publications on the Khibiny, the Belomorskaya lowland, the Dvinsko-Mezenskaya plain, the Timan Hills, the Pechora plain and the Subpolar Urals (See Table 2). Using the obtained data, we constructed point ecological ranges of communities with L. borealis and M. bifolium. We calculated mean values of stages of soil moisture and richness, standard deviation and confidence intervals of the obtained values at the level of statistical significance p< 0.05 (See Fig. 3, a and b). The cenotic connections were estimated by the number of forest types where the species were observed in different regions of the northern taiga. The change in the ecological positions of L. borealis и M. bifolium was traced by a change in their constancy in ecological series of communities by soil moisture and richness, created on the basis of PS Pogrebnyak's edaphotopic grid using geobotanical materials from the Pinega River Basin (See Fig. 4 and 5). In the course of the study, we revealed that the constancy indexes of L. borealis and M. bifolium in the northern taiga vary from west to east: for L. borealis the maximum values were recorded in the Khybiny and Dvinsko-Mezenskaya plain; for M. bifolium -only in Dvinsko-Mezenskaya plain (See Fig. 6, Table 3). The calculated ecological amplitudes (according to moisture and nutrient status scales) for both species are narrower in comparison with potential ones. We noted a shift in ecological positions from more humid and nutrient-poor in the west to drier and nutrient-rich stages in the east within the plain part of the subzone. The maximum amplitude by the moisture factor for both species were observed on the Dvinsko-Mezenskaya plain, while the largest nutrient status amplitude was detected in the Pechora lowland. The cenotic connections of both species might be explained by differences in ecological positions within the subzone: the maximum number of forest types with both species occurrence was noted for the Dvinsko-Mezenskaya plain; for the Pechora lowland, the maximum constancy indexes of both species were observed in spruce and larch forests on the well-drained plain and upland areas in the central as well as eastern parts of the subzone where a moderately continental climate is inherent. The minimum indexes were marked in pine forests of wet poorly drained lowlands in the western and eastern parts of the subzone. The paper contains 6 Figures, 3 Tables and 49 References.

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