Russia

In the tundra region of the north it sinks to 8 inches, while south of the central belt, in a region which includes the south of European Russia and the Central Asiatic Republics and the steppes and semi-deserts to the north of them, the prevailing winds throughout the year are from the dry north-east and rain fall therefore is scanty, in some places as low as 4 inches per annum, and agriculture depends on irrigation. A special problem of Russian agriculture is the irregularity of the amount of spring rainfall, complicated by the fact that this irregularity occurs in regions where the length of the snow covering varies from year to year in dependence on violent winds. A combination of poor snow covering and deficient spring rains leads to the terrible famines which are a recurrent scourge of south-east Russia. Re lated to this irregularity are such problems as the increasing desiccation of Turkestan, the present shallowness of streams which were navigable within recent historic times, and the drainage of marshes in the north by the slow elevation of the land. A general feature of the summer rainfall and of the May and June rainfall of the steppe is its liability to fall in sudden heavy showers, often accompanied by thunderstorms. This results in a quick run off of the water so that the effective moisture is small. In 1882 in Kursk province a heavy storm in July deposited within half an hour an amount of rain equal to 25% of the normal annual rain fall. Forest cutting in the upper courses of streams has greatly increased the denuding action of streams.

Certain regions form distinct climatic units. In this group, of course, fall the valley regions of the mountain zones, each valley often having a different exposure and different altitude. The east coast of the Black sea under the lee of the Caucasus has a milder climate and its rainfall (6o inches per annum) is of the same type as that of the west coasts of the Mediterranean, in dependence on the special pressure systems over the Black Sea. The region round Lake Baikal is much influenced by the presence of that body of water, especially in December before freezing sets in, when the combined influences of open water and of the liberation of latent heat during freezing cause the isotherms to loop north-eastwards around the lake. The special features of the eastern coastal region are discussed under Far Eastern Area (q.,v.) and for those of the Arctic fringe see POLAR REGIONS.

Soil study or Pedology as a scientific discipline owes its present position largely to Russian research, which has demonstrated that the soil is a distinct entity dependent on regional and climatic factors for its evolution and type. The vast extent of the Russian empire and the importance to its life of the Chernozyom (Cherno zent) or Black Earth, gave special opportunities for studying the characteristics of soil under widely differing climatic, geological, topographical and biological conditions. Foremost among these workers was V. V. Dokuchaiev (5846-5903) whose researches, published 1879-1883, included a cartography of Russian soils.

The Dokuchaiev Institute of Soils in Leningrad published in 1926 a detailed map in colour of the soils of Russia compiled under the direction of K. D. Glinka and L. I. Prasolov, with the assist ance of S. S. Neustruev, B. B. Polynov and N. I. Prochorov. Glinka's work on soils is of world-wide importance and the publi cation in 1928 by the Department of Agriculture of the United States of America of an English translation of his classic "The Great Soil Groups of the World and their Development" makes his results available for the first time to English speaking peoples.

An important series was published in English in 1927 by the Russian Academy of Sciences and includes thirteen pamphlets by different Russian soil scientists on various aspects of pedology affecting Russia. Fallou and Richtofen had previously recognized the importance of the study of the regional distribution of soils, but the definite connection of present climatic conditions with the geography of soil distribution was first laid down by Dokuchaiev and afterwards developed by N. Sibirtsev and K. D. Glinka. Russian scientists were pioneers in the detailed study of vertical sections of soils, which reveals important morphological characters of the various layers dependent to a large extent on climate. This study of soil horizons owes much also to Japanese and American investigators, while later the work of microbiologists (e.g., S. N. Vinogradski and V. L. Omelianski) and of students of colloidal action (e.g., K. K. Gedroiz) much widened the scope of study. The accompanying soil maps of Russia are based on the maps prepared by Glinka and Prasolov.

The Tundra.

The first main group is the tundra zone stretch ing across the whole of northern Russia. The name tundra implies treeless as opposed to forest lands, and two main zones can be noted. As one goes north-eastwards in Asiatic Russia, the climatic conditions become increasingly dry and precipitation ultimately reaches a minimum and there is much arid clayey and stony dry tundra, but in the remainder of the northern tundra zone there is greater annual precipitation. Scanty though it may be, this pre cipitation is often sufficient to cause the soils to be classed as humid, owing to low temperatures, slight evaporation and the permanent freezing of the sub-soil which seriously limits the draining off of surface water. The excessively moistened horizon above the frozen sub-soil, which thaws during the brief summer and turns the region into an impassable quaking bog, is called "talik"; it is coloured by ferric rusty spots and wedges of humus. This "glei" horizon of tundra soils retains its motley colouring when dried. The vegetative mass of moss, lichen and dwarf shrub tends to form peat, and "hillock tundra" is apparently due to the formation of a frozen core which cuts off the moisture supply of the surface moss, thus causing it to die. The decomposition of vegetation causes denudation and cracking, with ultimate gradual disintegration of the hillocks, between which the surface water collects and runs off.