The Timberline and the Subalpine Belt in the Caucasus Mountains, USSR^∗

Abstract

The timberline of the Caucasus Mountains has been differentially affected by anthropogenic processes, becoming increasingly lower towards the east and the south. This is because the natural characteristics of the subalpine belt were more favorable to nomadic and seminomadic cattle grazing with increasing continentality of climate. Preservation of even small sections of the natural timberline is extremely rare in the eastern Caucasus, while relatively undisturbed natural ecosystems are much more common in the subalpine belt of the western Caucasus. Anthropogenic effects have increased the predominance of grassy vegetation in this belt which now includes many meadow formations of long-standing hemixerophyllous, and subalpine, tall grass formations.

Timberline today varies in altitude between 2200 and 2750 m. The altitudes attained by the uppermost forest stands in different regions of the Caucasus depend not only upon the continentality of the climate and the degree of influence of “mountain mass,” but also upon the arboreal species involved. The upper limits of the boreal species (e.g., Pinus sosnovskii, Betula litwinowii) and the semi-arid region species (e.g., Quercus macranthera, and some Juniperus spp.) reach higher elevations with increasing continentality, becoming almost parallel to the July and August isotherms. The upper limits of the arboreal species that are related to the flora of the humid, oceanic climate (e.g., B. medwedewii and Q. pontica) fall with increasing continentality. Species such as Picea orientalis, Abies nordmanniana, and Fagus orientalis, belong to the floral elements of the mid-latitude, temperate, humid mountains, show little natural variation in maximum altitudes.

Thus the structure and altitude of timberline and the subalpine belt in the Caucasus reflects the original climatic gradients, west to east and north to south, and the increasing anthropogenic effects over a long period of time in these same directions. The various subalpine ecosystems are described, including straight-trunk forests, thin forests, thin and low forests, crook-stem forests, semicreeping crook-stem forests, creeping vegetative-migratory, crook-stem coppices, and dwarf woods. The importance of conservation of the subalpine ecosystems is stressed in terms of prevention of soil erosion, optimum water balance, and preservation of the floral and faunal gene pool.