Nature conditions
Dominance of massive block elevations in the tectonic structure of Altai is also emphasized by the presence at the north-west periphery of Altai and also in Zaissan depression and, partly, in Barun-Khurai depression, of the front terrace at the altitude of neighboring plains - to an average of 300-340 m in the north and west of the whole country, and about 450-500 m in Zaissan and Barun-Khurai depressions. In the eastern part of Altai mountain mountry, the pedestal of the front foothills and, sometimes, of rather considerably and even sharply elevated high mountain massifs are higher, especially in the direction from the north to the south. This is quite evident, because it is formed by the levels of intermountain valleys - Minusinsk depression (lowest altitude 240 m), Tuva depression (640 m), Ubsunur depression (743 m), Depression of the Great Lakes (1028 m), Shargyn-Gobi (948 m), Transaltai Gobi (1000 m).
Altai-Sayan mountain country is also an important watershed. The major part of the upper (mountainous) basin of Ob and Irtysh, the minor part of the basin of Yenissey, and basins of rivers flowing into the closed depressions of Kazakhstan, Dzungaria and Mongolia, are situated here. The latter are the big depressions of the northern part of Dzungarian Gobi (Urungu-Noor lake, which just recently has been isolated from the basin of Irtysh), a part of the Depression of the Great Lakes, the borders of Barun-Khurai depression, and also the closed depressions of the lakes Achit-Nuur, Ereg-Nuur and Tsagan-Nuur in the north and Alag-Nuur in the south, as well as of the biggest lake of the region - Uvs-Nuur (Ubs-Nuur). The mountain country is covered with a dense web of rivers (somewhere rivers flow through the big ranges).
However, contemporary congelation of Altai is rather moderate although Altai is a comprehensive centre of glaciations of the whole country: about 1500 glaciers of a general square ca. 910 km2 are concentrated here. The main center of congelation in Altai is a mountain knot Tavan-Bogdo-Ula, where the biggest valley glaciers are situated (chiefly in Mongolia). Another big centers of glaciation are the glaciers of Belukha, Northern-Chuysky Alps, Southern-Chuysky Alps, Mest-Ula, to a less degree - glaciers of Turgen-Ula and Mongun-Taiga. The ice cupolas of Tsast-Ula, Sutai-Ula and Tsengel-Ula are apparently remnants of the past, much stronger, glaciation. Congelation of high mountain massive Munkh-Khirekhan is very peculiar: small glaciers in narrow valleys exist as a result of gradual degradation of pendent glaciers, not forming a continuous ice cover of the tops. Some other ranges also have small glaciers and firn fields. In general, however, glaciers form only an insufficient part of the drain of the biggest rivers flowing from Altai mts. The annual melting of the rather thick snow cover plays a greater role, especially in northern and western parts of Altai, as well as in the knots of interception of wet air masses (orientation of which is mostly south-western).
Vegetational cover (principal characteristics)
However, at the western border of Altai some important factors of the influence of this giant mountain system on adjacent plains are visible. First of all, it is evident from the decrease of subzonal limits of forest-steppe and zonal limits of steppe and northern deserts southward (in the area of influence of mountains and in complicated conditions of low upland). This phenomenon is even more expressed in the east of Altai mountain country, where, under conditions of the "rain shadow" on the highly elevated plains, the Gobi-type deserts (in the south), then desert steppes (northward) and, finally, dry steppes and complexes "semideserts, dry steppes and genuine steppes" (in an insular conditions) are developed. This considerable shift of zonal limits nortward is, of course, noteworthy, but not unique: at the same latitudes the same shift northward is observed in the Turgai Hollow and in the north-eastern vicinities of Central Kazakhstan Upland.
The fact that Altai mountain country is situated on the border of two sectors of Northern Asia - West Siberian-Middle Asian-Himalayan and extreme continental Central Siberian-Central Asian-Indochinese - is also of a great importance. In general, this border runs next to 900 orient. long., but in Altai it is more complicated: it starts in an almost latitudinal direction along the Sayan range and Tchulyshman plateau, then - south-westward amidst Kuraiskaya and Chuyskaya steppes to the Ukok plateau - then, passing Tavan-Bogdo-Ula, eastward, to the Tsengel-Ula and Munkh-Khirekhan, south-eastward to Alag-Khirekhan, then again south-westward between Baitag-Bogdo and Ikh-Khavtgijn-Nuruu, and then - southward and westward through the ranges of Eastern Tian-Shan to the 800 meridian. This broken line represents the western limit of most continental phenomena (in high mountain conditions) on the Asian continent. Latitudinal and zonal borders also define difference between two basic systems of altitudinal zonality in AMC - with and without well developed forest belt (or belts), although the difference between these systems are not reduced to only this characteristic. The general composition of flora, vegetation, and formations of vegetation also display marked differences of these.
Animal world (principal details)
A history of Altai and Sayan was so that alpine belt of these mts. is currently inhabited by numerous arctic-alpine faunistic elements with disjunct distribution ranges. Such a complex is mot developed in Central Altai (Chuysky Alps, Ukok plateau), in East Tuva and Pre-Baikal region (Pribaikalye). Deserts. Semi-deserts, and steppes of southern part of the region are inhabited by a specific fauna combining Dzungarian and Central Asian elements. The beetles, especially Tenebrionidae, desert moths (Coleophoridae, Phycitidae, Cossidae, Noctuidae), spiders, reptiles, desert birds, bats and rodents are rather abundant.
Dry montane steppes are not faunistically rich but many highly specialized animals occur there. Spiders, beetles, reptiles (blizzards), various Passeriformes, rodents play a big role in montane-steppe faunistic complexes.
Forests, forest-steppes, and steppes of Altai and Sayan are most rich with animals. The fauna of these belts includes many species with rather wide distribution (Trans-Palaeoarctic, East- or West -Palaeoarctic). Because of specific conditions and isolating effect of mountain ranges, a good amount of such species is represented in Altai and Sayan by rather distinct subspecies or specific ecological forms. Tundras of different types are inhabited by specific fauna which includes, besides arctic-alpine elements, also rather high per cent of species endemic to the mountains of Siberia and South Mongolia.
It should be noted that the fauna of Altai-Sayan region is studied very irregularly. While the level of knowledge on the fauna of Rusian and Rudny Altai, Sayan and Pre-Baikal region is comparatively satisfactory, the vast areas in Mongolia and West China represent "white spots" in this respect. The data on the animal world of such isolated and interesting areas as the ranges Baitak-Bogdo and Adzh-Bogdo, Barun-Khurai depression, some ranges and reservoirs in the Chinese Altai are nearly absent. Therefore, it can be assumed that the real level of animal endemism in Altai and Sayan is (probably considerably) higher than it is currently estimated. This is especially true with regards to the fauna of spiders and insects; a study of these groups is most urgent at the present moment in view of resolving both taxonomical and zoogeographical problems. As it was emphasized by a well-known Russian zoologist and zoogeographist, O.L. Kryzhanovsky, a clarification of bigeographic limits is greatly based on the study of fauna of Invertebrata. This problem is especially actual for Altai-Sayan region situated within both Boreal and Ancient Mediterranean provinces.
Another problem is a study of rare and endangered species of animals in Altai and Sayan, including study of biology, distribution, and a monitoring of their population. The fauna of Altai- Sayan region includes a good number of rare and endangered species of mammals, birds, invertebrates, protected by Red Books of different level. However, estimation of a number and a condition of the populations of rare species is optimal within the natural limits of distribution ranges and not within the sites artificially outlined by administrative borders.