Chinese national geography Tibet Special Issue in 09, 2005.

Downstream of Yang Ni: Yangni River, originating from Milla Mountain, flows eastward, turns south after passing Bayi Town and joins the Yarlung Zangbo River. In the lower reaches of the Yangni River, an exposed sandbank divides the calm river into braided channels, with intermittent water flow, which nourishes the trees and grass on the sandbank and is also the fresh water source for farmland irrigation on both sides of the river. The valley is warm and humid, with an altitude of only over 2000 meters, which is in sharp contrast with the cold and arid plateau in northern and western Tibet. Photography/Xie Gang

The warm zone of Tibet is in the valley.

All creation, mostly pursue an unexpected effect. One day, a photographer from Sichuan said to me, "I'm going to shoot warm areas in Tibet." I think: the subtext of his sentence is that most people think that Tibet is a cold place, and the warm area he wants to photograph is unexpected. But I think Tibet is so big, how to grasp the warm area?

After a while, I almost forgot about it. Suddenly one day, a photographer in Jilin brought many photos, which he took more than a dozen times in Tibet. He gave these photos a general name: five canyons in the Himalayas.

After reading these pictures, I suddenly remembered the photographer who wanted to shoot "Tibet Warm Zone". I want to tell him that the picture in front of me now is "The Warm Zone of Tibet". Because the warm areas in Tibet are all in the "ditch", that is, in the river valley.

Not only the "warm zone" of Tibet is in the valley, but also the humanistic essence of Tibet is in the valley. For example, Lhasa, the largest city in Tibet, is in the Lhasa Valley, while Shigatse, the second largest city, is in the valley where the Nianchu River meets the Yarlung Zangbo River, Qamdo is in the Lancang River Valley, and Linzhi is in the Yangni River Valley. The towns in front are all in the valley, and so is heping town, the ancient county seat of Tibet.

Tibet is located on the Qinghai-Tibet Plateau, which is the highest plateau in the world. What is a plateau? A large uplift, the steep area around it is called plateau. Above the plateau, there are not mountains without valleys, but gentle places account for a large proportion. 46% of the land surface in Tibet is above 5000 meters above sea level, 46% is above 3500-5000 meters above sea level, and 8% is below 3500 meters above sea level (data comes from Agricultural Geography of Tibet). This is a very interesting set of data. First, in this set of data, you can see that the Qinghai-Tibet Plateau is really too high. There is another phenomenon: the higher the altitude, the larger the area, and the lower the altitude, the smaller the area. In fact, this is exactly what the plateau should have, while the plains and mountains are just the opposite. Although there are few areas below 3,500 meters above sea level, accounting for only 8%, these areas are basically river valleys, and Tibet's prosperity lies in this 8% river valley.

Upper reaches of the Chu River: The Shan Zong Anti-British Castle on the cliffs makes us no longer doubt that this is the ancient city of Gyangze at an altitude of more than 4,000 meters in southern Tibet. Gyangze is located on the north bank of Nianchu River, a tributary of Yarlung Zangbo River. Every July, Gyangze becomes lively because of the blooming of rape flowers. In, the Chu River Basin was another rich and prosperous place in Tibet. Cold-tolerant rape flowers grow vigorously in sufficient sunlight, and the oil extracted from rapeseed is of high quality. Photography/Zhao Chunjiang

The valleys in Tibet are all charming valleys.

The valleys in Tibet are charming valleys. They are the only remaining valleys in China that have not been polluted by industrial civilization. The Yarlung Zangbo River, the largest river in Tibet, is still flowing brightly without a dam. Some tributaries of the Yarlung Zangbo River are shallow, and Sha Ou is clustered, unlike the inland river, where people are noisy and birds don't lay eggs. One year, I went to the airport from Lhasa, and I was driving along the Lhasa River. I saw waterfowl flying everywhere on the shore, in the water and on the beach: red-spotted ducks, crested ducks, spotted geese, brown-headed gulls and red-footed snipes in pairs, chasing and playing.

From April to May, the Yangni River Valley is full of peach blossoms. If red mist fills the air, it will light up the whole valley. From this point of view, the valleys in Tibet seem to be beautiful and full of idyllic tranquility, but if you look up or overlook, you will see the snow peaks above beautiful countryside. You realize that it is not enough to describe the scenery of Tibetan valley with beautiful countryside. Above the countryside, magnificent and lofty. In the small town school in Milin County, you can stand by and watch the Yarlung Zangbo River, and you can see two snow peaks, Nangabawa and Galabalai, which are more than 7,000 meters above sea level, facing each other on both sides of the river. Those climbers set out from the peach-blossom villages in these valleys to get close to the snow-covered peaks.

Middle reaches of Yarlung Zangbo River: Peach blossoms in Milin area are a must-see scenery in southeastern Tibet in spring. In the middle reaches of the Yarlung Zangbo River, the broad valleys are pregnant with fertile soil and fertile fields, and the village ridges here are hidden in peach forests. Some people compare this place to Suzhou and Hangzhou, but I don't know that the peach trees along the Yarlung Zangbo River are not artificially cultivated ornamental varieties. They have beautiful colors and huge branches, and it takes several people to hug a peach tree. On both sides of the Peach Blossom Valley are extremely high mountains with an altitude of 5,000 meters or even 6,000 meters, and snow peaks shine among the clouds. Rich ravines, magnificent scenery, shocking. Photography/Hua Yang

Warm places are formed by rivers.

In Tibet, the significance of rivers to people lies not only in solving the problems of drinking water and irrigating fields, but also in solving the problems of transportation and communication. Most importantly, the river creates a warm place on the plateau. Why do you say that?

We know that the temperature decreases with the elevation. Some experts have calculated that the temperature in Tibet drops by 0.58℃ at every altitude 100 m, whereas the temperature rises by 0.58℃ at every altitude 100 m..

The average elevation of the Himalayas on the southern edge of the Qinghai-Tibet Plateau is above 6,000 meters, and the average elevation of the Gangdise Mountain on the east-west direction of the plateau is also above 5,500 meters. The middle reaches of the Yarlung Zangbo River, sandwiched between these two mountains, have an altitude of 3000-4000m, and the relative height difference is1500-2500m. The average height difference between Hengduan Mountain Range and its valley in southeast Tibet is 1000-2000m. Under such a height difference, the annual average temperature in the valley is more than 5℃ higher than that in the mountains and plateaus, and the temperature in the valley is higher in summer.

Rivers flow on the high-altitude and cold plateau, and the plateau is cut into gaps by the erosion and transportation of rivers (there were also the erosion and excavation of glaciers during the ice age). In the process of plateau rising, rivers refuse to rise through cutting, the earth is rising, and rivers are falling. The two are struggling, and the result of the struggle is that the surrounding area is rising, while the valley is deepening or rising slowly. Finally, the valley became wide and deep, and the altitude became lower and lower, then the valley became warmer and warmer, and finally it was far away from the cold on the plateau.

"Hu Line" in Tibet: Draw a line from Baqing to Geelong.

The topography of Tibet has a remarkable feature: it is high in the northwest and low in the southeast; The northwest is basically a plateau and there are many valleys in the southeast; The average elevation of Ali and Qiangtang Plateau in the northwest is above 5,000 meters, while that of Medog and Chayu in the southeast is below 2,500 meters, and it is only at 100 meters until the mouth of the Yarlung Zangbo River. From Pasigart to Ali, the scenery you see is like from the equator to the South Pole or the North Pole.

Most rivers in the northwest plateau of Tibet are inland rivers, which are short and weak and flow to plateau lakes. Rivers in the southeast are different. Most of them are outflow rivers, mostly originating from the northwest, but flowing to the southeast, which is already a big river with a wide river and abundant water. These river valleys are places where agricultural production and human beings gather, and they are rich places in Tibet. The population distribution in Tibet is very similar to that in China, and it is extremely unbalanced. Specifically, the northwest is vast and sparsely populated, and the southeast is densely populated. You can also draw a "Hu Huanyong Line" in Tibet, from Baqing County in the northeast to Jilong County in the southwest. To the west of this line, the land area accounts for 60% of Tibet, and the population only accounts for 15%. To the east of this line, land accounts for 40%, but population accounts for 85%. To the east of this line are agricultural areas, forest areas and semi-agricultural and semi-pastoral areas; To the west of this line, there are pastoral areas and only a few agricultural areas; To the east of this line is a warm and humid alpine canyon area; To the west of this line are very cold and dry plateaus and extremely high mountains.

The fertile land in Tibet is mainly concentrated in "one river and two rivers", that is, the middle reaches of the Yarlung Zangbo River and the middle and lower reaches of the Lhasa River and Nianchu River, which are also tributaries of the Yarlung Zangbo River. The middle reaches of the Yarlung Zangbo River basically flow on the plateau, with small gradient, slow flow rate and wide valley, 2-3 kilometers wide in some places, and the confluence of tributaries is 10 kilometers wide. These places are fertile and densely populated, and more than 80% of Tibet's population is gathered here.

In addition to "one river and two rivers", there is another region in Tibet that is very rich, that is, the "Sanjiang region", that is, the Nujiang River, the Lancang River and the Jinsha River, which refers to the upper reaches of the Three Rivers. These places are deep river valleys, but some important towns in Tibet are located in river valleys, such as the border dam of Nujiang River and Luolong. Changdu, Mangkang and other places in the Lancang River Basin; Jiangda on the Jinsha River. Sanjiang Gorge, with high temperature and abundant precipitation, is an idyllic paradise in Tibet.

Tibet at the southern foot of the Himalayas also has a rich land. The uplift of the Himalayas from the Indian plain stopped the clouds and water vapor from the Indian Ocean from moving northward, and these turbulent clouds and water vapor became abundant precipitation in the process of climbing. These abundant precipitation merged into a fast-flowing river, which cut it into pieces as the Himalayas rose. Some valleys are deep and long. Along these winding valleys, you can cross the Himalayas and reach Shan Zhinan from the north of the mountain. These valleys are not only passages, but also fertile soil for survival.

These valleys in the southern Himalayas are counted from west to east: Pulan Valley, Geelong Valley, Zhangmu Valley, Yadong Valley, Cuona Valley and Zi Long Valley, all the way to the Yarlung Zangbo River bend where Medog is located. There are also some smaller river valleys, such as Gamagou and Chentanggou. Although the scale is not large, the climate is warm and the scenery is not inferior. What I want to say here is that there is still a large area in the southeast of the Himalayas illegally occupied by India, which is the area south of the so-called McMahon line. This area, which is close to Zhejiang Province, is the warmest area in Tibet and a place where rice can be grown in Tibet. There are many valleys in this area, including Tea Fish Valley, Danba Valley, Xiba Canyon and Carmen Valley. These valleys are undoubtedly rich and beautiful.

It should also be mentioned that there are several valleys on the Ali Plateau in the northwest. Although there are few rivers in the Ali Plateau, only a few valleys are just fertile soil in this area. One of the more famous is Xiangquan River and the other is Shiquan River. Because I went to the ruins of Guge Dynasty, I lived in a small village by Xiangquan River. One morning, I stood on a hillside and looked at the fog floating on the river. The fields are full of harvested highland barley, and the village wakes up in the morning fog. Cattle and sheep poured out from each family, merged into a ball and were driven to the grass by the river by herders. At that time, cowbells rang and smoke billowed. I suddenly understood why there was a Guge civilization here, and my past impression of the cold and poverty in the Ali Plateau vanished.

The magic of Tibetan valley

Why do people live in these valleys? Not only because they are warm, but also because they are rich.

These valleys have magic that is not found anywhere else. One year I went to Mount Everest and walked along the Yarlung Zangbo River Valley. The sea of rape flowers under the blue sky is dazzling yellow. After returning from Mount Everest, we took another road and entered the Nianchu River Valley. The Chu River in 2000 was a tributary of the Yarlung Zangbo River, and the Chu River basin in 2000 was the main agricultural area in Tibet, and it was also a rich place in Tibet. In this valley, we met the sea of rape flowers again. It turns out that rape is one of the most widely distributed and cultivated crops in Tibet. Why do Tibetans plant rape? It turns out that the quality of rape in Tibet is better than that in the mainland. I read a book that said, "Tibetan rape has the characteristics of large grain size, high yield and good quality." The 1000-grain weight is 4.5-6.7 grams, which is twice as high as that in inland plain areas. At present, three varieties with oil content above 50% in China are all distributed in Tibet. "

Not only rape, but also some crops produced in Tibet must have high yield, large size and good quality. For example, sugar beet in Tibet is 20-30% heavier than sugar beet in northern China. Vegetables in Tibet are equally excellent. Radish is more than 20 kilograms, cabbage can reach 50 centimeters in diameter, and four dried garlic is one kilogram.

Even the forests in Tibet have many characteristics compared with other places. The spruce and fir forests in Linzhi and Bomi areas of southeast Tibet are rare in the world because of their large tree height and high timber accumulation. Several woodlands in Bomi area, 200-year-old spruce, have an average diameter of 92 cm and a height of 57 meters, and the amount of wood per hectare reaches 2000 cubic meters.

Why are there these magical things in the valleys of Tibet?

Anyone who has been to Tibet will be deeply impressed by the blue sky in Tibet. In fact, the blue sky in Tibet is a unique advantage, which is also the reason why crops and forests in Tibet grow better than those in other places.

Although the temperature in these places in Tibet is still lower than that in the inland plains at the same latitude, the air on the Qinghai-Tibet Plateau is thin, with less dust and high transparency. In addition, the rainy season is short, there are many sunny days, and the plateau has sufficient sunshine and strong radiation. When mainlanders go to Tibet, they will get sunburned if they are not careful. This is because the radiation is stronger than that in the mainland. And these are exactly what crops and plants need to grow. Low temperature in summer, long growth period, strong photosynthesis and abundant organic matter are extremely special conditions for the growth of crops and plants in Tibet. Is this God's compensation for the cold in the plateau?