Vegetation of the Central Great Caucasus Along W-E and N-S Transects

Abstract

The Great Caucasus covers a significant west to east climatic gradient along its main divide (see Chap. 1). The highlands of the western Caucasus are humid (up to 2200 mm of precipitation per year) and dominated by mesophilic taxa, the highlands of the eastern Caucasus are more continental, with dry summers and an increasing fraction of xerophylic taxa (<800 mm of precipitation per year). Half of the annual amount of precipitation falls on the cold season, therefore large areas of mountains are covered by perpetual snow and glaciers. The annual temperature amplitude is small. One of the features of the Caucasus high mountains, which distinguishes this mountain system from other mountains of Europe are sharp climatic and thus, vegetation changes over relatively small distances. An obvious example is a S-N transect along the ‘Georgian Military Road’. This transect clearly shows how semi-desert vegetation becomes substituted by steppe, open arid woodland, mesophilous beech forest including the beech forest types with Colchic elements, then high mountain meadows, chiono- and kryophilous herbaceous and relict scrub communities even in snow-beds, and near-glacier micro-habitats. Within this transect local shelter by mountains can create is continental oroxerophilous vegetation islands. Interior valleys are protected from both cold and humid air mass penetration from the north explaining many relict xerophilous species of past xerothermic periods (Kharadze 1948).