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Shri Ashtapad Maha Tirth - II
the atmospheric circulation, and the amount of solar radiation, all of which are interrelated with temperature and elevation. The high plateau receives large amounts of solar radiation and small amounts of precipitation. Thus, across Byang-thang glaciers are not so extensive as those in the surrounding mountains. Plateau-type glaciers are small ice caps or flat-top glaciers. The high reaches of the western Kun-luns receive large amounts of precipitation from winds blowing in from the west, so glaciers there are very large. The south slopes of the Himalayas, especially in the east, receive more rain from monsoons than the north slopes, and so have more glaciation. Between 1950 and 1960 glaciers on the Tibetan plateau were reported to be shrinking, as were the glaciers in the European Alps. In the Kun-luns, the Pamirs, the Himalayas, and the Kara-korum mountains, glaciers increased in the 1970s, but those in the interior of the plateau did not increase. Of 116 glaciers studied by scientists over the past ten to thirty years, 62 are decreasing and 32 are increasing. Agriculture on - The Roof of the World Tibet has the highest upper limit of agriculture in the world. The climate is especially suited to wheat and barley, and cold-resistant highland barley can be cultivated even at 15,500 feet (4750 meters). The most important agricultural regions are along the Yarlung and gTsang-po rivers, the Nyag-chu (Nu Jiang), the rDza-chu (Lancang Jiang), and the 'Bri-chu (Jinsha Jiang). The elevation varies in these regions between 9000 and 13,500 feet (2700-4100 meters). Weather is mild and cool in the growing season, and the temperature rises slowly in spring. Rainfall is not extreme and usually is limited to night hours so that there are numerous sunny days. Second harvests are possible in some areas: barley followed by wheat, barley followed by millet, or rice followed by barley. The high-altitude agriculture is possible because the plateau, at its great height, absorbs large amounts of solar radiation, and the air close to the ground is heated by radiation from the land. The temperature on the plateau is higher, especially during the growing season, than on steep mountains in other parts of the world at the same elevation and latitude. Rice and maize can be grown only at lower elevations; thus rice cultivation in Tibet is possible in the deep valleys in the southeast and around the huge bend in the gTsang-po where it turns south toward India. Rice crops are much more common in neighboring regions such as the south slopes of the Himalayas and in Yunnan and southeast Asia. In addition to cereals, peas, and potatoes, which grow in many areas, certain regions are especially suited to crops that are not widespread. Apples, walnuts, and pears grow in the central gTsang-po valleys, while tea, grapes, tangerines, bananas, and oranges grow in the southeast. Jujube and apricots are plentiful in mNga'-ris in the west. At lower elevations in many regions, cabbage, tomatoes, cauliflower, onion, garlic, celery, radishes, turnips, and strawberries can be grown. Recently, additional kinds of crops have been cultivated experimentally.
Ancient Tibet
300
