The Vegetation of Roadsides in Taiga and Tundra Zones of West Siberia
The natural colonization of roadsides is considered. Studied highway extends through the central and northern regions of West Siberian plane and crosses taiga and south tundra zones. Species composition of roadside communities includes 257 species of higher vascular plants, 8 species of mosses and 4 species of lichens. 43 species with high partial activity take the greatest part in colonization of roadsides. At the northern segment of the road they are wide-spread pioneer species but at southern segment - meadow grasses. Along the whole road perennial plants of aboriginal flora are predominate. Synanthropic plants including ruderal annuals show noticeable activity only at southern segment of studied road. The vegetation of roadsides is represented by communities of different stages of primary succession. At the base of floristic similarity characteristic groups of communities for different zones (subzones) of vegetation were distinguished. Sparse grass-horsetail communities with small number of species without moss or lichen cover are usual in tundra and forest-tundra. Communities with well-developed moss cover and constant occurrence of northern shrubs and low shrubs are also described at the forest-tundra. To the south from forest-tundra starting at north taiga subzone meadow grasses and legumes increase their occurrence in roadsides colonization. The development of meadow communities at roadsides in north taiga subzone allows considering these ecotopes as main ways of meadow vegetation migration north from its natural limits.