80-year-old Siberian larch plantations situated on the border of southern and middle taiga subzones in Eastern Fennoscandia were studied. Total surveyed 6 forest sites located in the landscape with respect to the same environmental conditions. After the larch plantations had been planted in 1935 by Finnish foresters, studied forest communities developed without noticeable human interventions. Species composition of larch communities was defined within the boundaries of a permanent plot, on the others the forest sites within the borders of the natural forest associations, which are comparable in size to the size of permanent plots larch communities. Analysis of the forest stand characteristics of the studied forest sites showed that the Siberian larch plantations are well adapted and have a high competition ability compared with spruce and pine stands. The conditions generated by Siberian larch proved to be quite favorable for many species of ground cover: the number of vascular plant species was by two times higher in the larch forest stands than in the neighboring zonal spruce stands of the wood sorrel and bilberry types. The structures of ground cover in the larch forest stands are more complex: first layer was comprised by plant species that prefer low canopy density and fertile soils; the second layer was presented by shade tolerant plant species.

At the same time, the projective cover of mosses decreased although the number of moss species and their patchiness were increased. In spite of the markedly different number of species, of the ecological and ecological-coenotic structures of the studied forest communities were differed marginally. The number of species in the larch forest stands increased by both shade-tolerant and light-demanding species. Improved soil fertility in the larch forest resulted in an increase of the number of meso-eutrophic species that are typical for southern taiga zone. Generally speaking, the introduction of larch into zonal communities of spruce forests influences on the structure of ground cover structure more significantly than the variation of biotope factors within the study area.