Elevational Distribution of Alien Plant Species in the Western Caucasus

The elevational distribution of 100 alien plant species in the mountainous part of the Western Caucasus is considered. They include herbaceous (59%) and arboreous (41%) plants. Most of the plants originate from North America and East Asia; 57% are cultivated plants. The maximum species richness is concentrated in the lower zones of mountains with a more favorable climate, high population density, and significant human impact. With an increase in the elevation above sea level, their number decreases. This is typical of the majority of mountain systems in the temperate zone. Only 17 alien species are present above 1000 m a.s.l. They are mainly accidentally introduced annual herbaceous plants of North American origin. Most of them are widespread in the Western Caucasus, in many regions of Russia, and in Europe. Above the timberline in the subalpine belt (2000 m a.s.l.), one species is noted—Matricaria suaveolens. The differences in the elevational distribution of alien species on the southern (Black Sea) and northern (Kuban) macroslopes of the Western Caucasus are shown. It has been suggested that the import of diaspores with materials used in the construction and reconstruction of roads and the building of tourist infrastructure and other objects is the main way of penetration of alien species into the upper mountain belts of the region.