Analysis of high-mountain vegetation of the Kurai Ridge

The paper presents a taxonomic, areographic and be lt-andzonal analysis of the high-mountain flora of the Ku rai Ridge. The flora of the region in question contains 312 species of plan ts, referred to 143 genera belonging to 48 families. Analysis of the ta xonomic structure of the high-mountain flora of the Kurai Ridge has shown the following most abundant plant families: Asteraceae, Ranunculaceae, and Poaceae. For the variety of the genera, the following genera are pre dominant: Carex, Pedicularis, Salix, and Oxytropis. The areographic analysis has demonstrated that the said species are of the North Asian (21 %), South Siberian (19.4 %) and Holarctic (17.4 %) origins. D ominant in the beltand-zonal range are the following species: high-mou ntain (23.2 %), lightconiferous forest (17.7 %) and Arctic Alpine (17.4 %) species. In general, the composition and structure of the high-mountain flora of the Kurai Ridge are determined by its geographic position at t he boundary of Central and South-Eastern Altai and by decrease in the amou nt of precipitation in the south-eastern direction.


Introduction
The caenotic and floristic variety of the high-mountain belt of the Kurai Ridge is related to its geographic position, variability of the landscape forms, the composition of the rocks forming it and inhomogeneity of the climatic conditions. All these factors lead to formation of great caeno-floristic variety in the small territory [1]. Over the recent years, the relevance of studying the high-mountain flora of Altai has considerably grown due to essential changes in the character of its economic development. P.N. Krylov's works contain the first data on the floristic variety of the highlands of Altai; he was also the first to identify the belt-zonal groups in the high-mountain vegetation of Altai.
The most complete and detailed data on the high-mountain vegetation are contained in the works by A.V. Kuminova [2] and V.P. Sedelnikov [1]. In the works by M.P. Danilov [3,4], the inventory is taken of the ridge flora, with taxonomic and geographic analysis made based on the obtained data.
The objective of the study: to make the taxonomic, areographic, and belt-and-zonal analysis of the high-mountain flora of the Kurai Ridge.

The area of the study
The Kurai Ridge is a mountain range which serves as a watershed of the two biggest rivers of the Katun and Chulyshman basins (the Chuya and Bashkaus Rivers). It is of south-eastnorth-west trending within the Ulagan and Kosh-Agach districts of the Republic of Altai. It is 140 km long and 40 km wide. The ridge stretches in the north-western direction from the Chikhachev Ridge to the Aigulak Ridge. The Sarulukol Depression is north-west of it, the valley of the Bashkaus River is in the north, and the Kurai and Chuya Depressions are in the south. The highest peak of the ridge, 3,446 m, is situated in the upper reaches of the Ortolyk River [5,6]. The climate of the territory under study is sharply continental, the average air temperature in January is -32.1° C and +13° C in July The total annual precipitation is 110 mm. The vegetation period lasts from 50 to 70 days.
In accordance with the floristic zoning carried out by S.I. Molokanov [7], six floristic districts -Kurai, Aktash, Chuya, Kokorya, Kavuri, and Saratan districts -have been identified on the Kurai Ridge. Kosh-Agach (745 species) is the most floristically abundant district, which is related to the presence of all the vegetation belts in its territory, from the steppe belt to the nival belt.
The high-mountain vegetation of the Kurai Ridge is subdivided into two belts: subalpine and alpine.
The subalpine belt stretches from 1,800-2,500 m asl. In the vegetation cover, the formation Betula rotundifolia prevails in the complex with subalpine meadows. Highmountain and meadow steppes commonly occur on the southern slopes of the subalpine belt. Tallgrass subalpine meadows occur in the north-western part of the Kurai Ridge, and their grass tier consists of Aconitum altaicum, Delphinium elatum, Saussurea latifolia, Stemmacantha carthamoides, etc. Lowgrass subalpine meadows occupy riverine habitats, while in the grassy tier Astragalus frigidus, Geranium richardsonii, Rhodiola rosea, and Saussurea frolowii prevail.

Results and discussion
The flora of the high-mountain belt of the Kurai Ridge consists of 312 species of higher vascular plants, which refer to 143 genera from 48 families. Angiosperms are prevalent, with 301 species present, constituting 96.5 % of the total number of species. Cryptogam plants are represented by 4 species, while gymnosperms are represented by 7 species (Table  1).
Analysis of the taxonomic structure of the high-mountain flora of the Kurai Ridge has shown the following families to be abundant in species: Asteraceae (9 %), Ranunculaceae (7.8 %), Poaceae (7 %), Caryophyllaceae (6.1 %), Rosaceae (6.1 %), Cyperaceae (5.8 %), Scrophulariaceae (5.8 %), Fabaceae (5.4 %), Apiaceae (4.8 %), and Gentianaceae (4.2 %) ( Table 2). These families include 193 species, which is 61.9 % of the total flora. Certain families are also present, which are scarce in terms of the species composition but play a significant role in forming the high-mountain vegetation, with Alliaceae, Boraginaceae, Brassicaceae, Ericaceae, Lamiaceae, Polygonaceae, Primulaceae, Salicaceae, and Saxifragaceae among them. These families include 65 species, which constitutes 20.8 % of the total flora. For the variety of genera, the following genera are dominant: Carex (9.8 %), Pedicularis (7,7 %), Salix (7 %), Oxytropis (5.6 %), Potentilla (5.6 %), Gentiana (4.9 %), Aconitum (4.9 %), Saxifraga (4.9 %), Allium (4.9 %), and Saussurea (4.2 %). These genera contain 85 species, which is 27.2 % of the total composition of the flora (Table 3). The areographic analysis was made based on the comprehensive study of the data provided in the works by L.I. Malyshev and G.A. Peshkova [8]. Analysis is one of the main sources for revealing the details of the floristic genesis. Izt showed predominance of the North Asian species (21 %), which is related to development of the most recent centers of species formation within the boundaries of the long trans-Asian mountain belt. The endemic species of the Kurai Ridge are the most specific component of the flora, reflecting the autochthonous trend in the flora development. 24 endemic species were identified among the high-mountain flora, which accounted for 7.7 % of the total flora, the greater part of which grows in rocky and arid habitats (Fig. 1). The belt-zonal analysis of the floristic structure allows us to evaluate the regional floras in terms of compliance of its composition with the current orographic and climatic conditions and allows us to identify the features testifying to the stages of the evolution of the flora. The results of the analysis showed that most species are related to the highmountain belt-zonal complex (23.2 %), which is typical of the Kurai Ridge (Fig. 2).