Mongolia

3. South-eastern Mongolia, on the inner or Chinese side of the Gobi, is like the north-west in being much more diversified in character than the central portion of the plateau. It contains an outer and an inner series of chains. The outer series forms parallel ranges (Suma-Khada, Ta-tsing-shan, Khara-narin-ula and others) which if not homologous with the great Khingan, are at any rate analogous to it and constitute the south-eastern scarp edge of the whole plateau, sloping gradually north-westward to the Gobi depression. The inner series is made up of denuded f old chains partly within the line of the Great Wall (in the neighbour hood of Kalgan) and forms the frontier-zone between Mongolia and the alluvial plain of north China. Between these two series is an intermediate zone of lower elevation and this is economically the vital part of "Inner Mongolia." Of a different character, how ever, is the more or less level Ordos plateau contained within the immense Hwang Ho loop. It has the appearance of an ancient stable block; its surface of sandy or loamy soil is in parts not unsuited for agriculture, especially with irrigation. The surface of Inner Mongolia is marked by numerous small brackish or salt lakes.

Differences in Climate and Vegetation.

The differences here noted between the three major regions of the Mongolian tableland are further accentuated on climatic and vegetational grounds. The plateau as a whole is naturally characterized by dryness and great seasonal range of temperature, i.e., "continen tality." During the winter half-year the Asiatic high pressure system is centred over the northern edge of the plateau, while pressure is lowest in June, July, August. The whole area is one of outflowing winter and inflowing summer winds. The latter come from two main directions : west or north-west affecting Outer Mongolia, and south-east (monsoonal) affecting Inner Mongolia. The difference in mean temperature between the north west and south-east of the plateau is considerable, amounting to about F on the average of the year. But the contrast is much greater in winter than in summer when the temperature is relatively uniform over the whole area. The Altai-Sayan moun tain-complex in the north-west partakes essentially of the Siberian climatic regime; the winter cold and annual range of temperature are here at their maximum. The total annual rainfall (including heavy snowfall) averages 10-20 in., but coming as it does from the west is not of the "monsoonal" type. Winds are probably not so strong or frequent as in Gobi, for Urga (on the edge of the region) is reported to have calms on 4o% of the days in the year. It has a mean January temperature of 15° F and a mean

July temperature of 64° (tempered by altitude) showing an abnormal range. The average annual rainfall here is between 9 and Io inches, which is less than that of the north-west as a whole. The Gobi represents the classic example of a region with an extreme or continental climate. Winds blow unimpeded almost all the year round, mainly from the north-west. The rainfall is almost negligible in the real Gobi ; the dryness is due to the fact that rain-bearing southerly winds have deposited their mois ture on the successive high marginal ridges which border the plateau on the south-east.

On the other hand the Pacific influence is reflected in the climate of Inner Mongolia which more than any other part of the plateau is definitely affected by the monsoonal regime of summer.

In the winter half-year winds are predominantly from the north west bringing extreme cold; while dust-storms arising in Gobi are a common feature. The summer monsoon from the south east brings the rains, averaging from I o to 15 inches annually along the plateau edge, beyond which they rapidly die away.

The vegetational conditions correspond closely to these con trasts of climate. The north-west has Siberian affinities. On both sides of the Sayan are dense forests of larch, cedar, pine and deciduous woods characteristic of the Siberian flora. These decrease to their southern limits on the northern slopes (only) of the Khangai and Tannu-ola. With this exception the surface of this lofty mountain-complex is marked by prairie-land, fur nishing excellent pasture in the wide basin-like valleys or plains.

The rivers of the Urianghai basin are abundantly stocked with fish and the meadow-land of the floor of the basin affords very rich pasture; the area also contains valuable mineral deposits, and is capable of supporting a larger population. From the Tannu-ola southwards, the treeless zone extends to the unforested Altai ; the gravel surface generally yields dry prairie-land.

The Gobi division, as a whole, must be regarded rather as a poor steppe-land than desert proper. On its northern limits around the Kerulen river, high mountains bearing larch and spruce woods alternate with river valleys which afford areas of good pasture. Steppes succeed southward, merging into the Shamo or Gobi proper which is barren of vegetation save in spring and early summer. Physiographically, climatically and vegetationally Gobi is a very real divide between Inner and Outer Mongolia, whose affinities in a physical sense are with China proper and Siberia respectively.