< h1 class="pgc-h-arrow-right" > introduction</h1>
"The woods are shady, the song is up and down, the tourists go and the birds are happy." This is a passage about trees in the Song Dynasty poet Ouyang Xiu in the "Record of drunken Pavilion".
Roughly speaking, after the humans leave the bushes, the birds begin to get excited and enjoy their unique space.
It can be seen that trees have a very important position in both ancient and modern people. They are the main producers of oxygen, which is extremely important for the improvement and regulation of the ecological environment, and is also an important material for people's production and life.
In our country, it is said that there is a county that has been without trees for thousands of years, and after scientists have tested there, they also said that they could not do anything. Among them, millions of dollars invested in tree planting research have also been wasted. However, there is no shortage of trees to look up to
Lai land, there is no lack of abundant rainfall. So why can't scientists do anything about it? Why can't there be trees here?
<h1 class = "pgc-h-arrow-right" > first, too much precipitation affects tree growth</h1>
The only county in the country that cannot grow trees is Nagqu County, located in the northwest of the Tibet Autonomous Region, at the intersection of the Tanggula Mountains, the Nianqing Tanggula Mountains and the Ganges Mountains.
It is connected to Changdu to the east, Ali District to the west, and Lhasa and Nyingchi to the south. The total land area is 369674 square kilometers, and the stable living population is about 500,000.
It is such a geographically superior place, but apart from the vast soil and grassland, there is not a single tree to be seen.
After several years of testing, the scientists concluded that it was impossible to plant trees. One of the main reasons for the increase in the number of people here is actually precipitation.
In general common sense, precipitation is one of the necessary conditions for plant growth, even in desert areas of ant forests and other green belts, can not be without water.
The subarctic semi-humid climate of the plateau allows for year-round precipitation, and the abundant amount of water is basically all over the mountains, but this has brought great obstacles to the growth of trees.
Excess water leaves the tree's rhizomes blistered for a long time, reducing the ability to absorb stored nutrients.
The cold climate here keeps the rain from evaporating, which leads to the decay of the roots of the trees, leaving them with no chance to continue growing.
According to statistics on the climate, there are strong winds here about 100 days a year, the average temperature is negative 2.1 °C, and when the coldest, the temperature can reach minus thirty or forty degrees. It has only 2886 hours of sunshine throughout the year, which means that it has only three months of sun exposure.
Under such an environment, trees have no chance to grow. Some say that by planting some cold-tolerant trees here, maybe the problem will be solved.
Scientists do, but whether it's introducing trees from the Arctic Circle or breeding hardy plants before planting them. The result is the same, trees can't grow here.
All in all, when excessive precipitation and alpine atmosphere are mixed together, it seriously affects the planting and growth of trees.
In addition, long-term unchanging permafrost is also one of the important reasons affecting the growth of trees here.
<h1 class = "pgc-h-arrow-right" > second, the permafrost that does not mature</h1>
More than half of the nearly 370,000 square kilometers of land in Nagqu County are frozen soil layers, and although it is between 29° 55′ and 36° 30′ north latitude, the altitude has exceeded 4,000 kilometers. That is to say, it does not have the high latitude of Heilongjiang, but it has the winter low temperature that only the Heilongjiang region has.
Under the permafrost, basically no other plants can grow and reproduce here except grasslands. Some scientific studies have shown that moving soil can preserve sufficient soil nutrients and water, and timely supplement trees with water and fertilizer to allow them to thrive. But in Tibet, frozen soil is not a good thing, and the truth of "permafrost is useful" in the northeast region is also not applicable here, and there are 5 main negative effects it brings.
The first is to freeze the plants. Here, the main cold is the subtropical and tropical plants, and the freezing will make their cells freeze, causing the cell lining to rupture, so that the cells of the plant are dispersed too quickly, causing local or total death of the plant. This is also the main reason why plants do not adapt to survive here after breeding.
Plants near the Arctic or Antarctic are hardy but do not accept too much water, while in subtropical and tropical regions, plants prefer places with a lot of water. After the two are bred, their advantages are not combined. New species either prefer water or cold.
The second negative effect is that the leaves are in a cold environment for a long time, and when the temperature is raised, they will lose water at an extremely high rate. This is the most important manifestation of all kinds of plants and trees after they are damaged by frost.
The third is to affect the germination and growth of trees. The main reason here is that after the rhizome is frozen, some of the water in the tree is lost, and some physiological functions are also lost, resulting in deformed development or non-development, and finally it will die in the process of continuous loss.
The fourth is that it affects the yield of trees. Under the combined influence of cold weather and permafrost, even if the trees here can grow, their numbers will gradually decrease until the species disappears here.
The fifth is the direct cause of plant death, which is a common phenomenon in the vast majority of regions.
In general, permafrost is the main reason for the growth of trees here, and the cold climate makes the trees worse. The extremely thin oxygen here is also one of the main reasons for the growth of trees.
<h1 class = "pgc-h-arrow-right" > three, thin air</h1>
Although carbon dioxide is an important factor in restricting plant growth and combining effects, the oxygen content in the air is the main factor restricting their growth.
About 500 million years ago, when the oxygen content in the Earth's atmosphere reached 10%, plants had a greater opportunity to develop. Under the action of plants, oxygen has been maintained at today's levels.
In the Nagqu region, if the oxygen levels in the air are similar to those in other places, the vegetation will not grow. Mainly because of the excessive precipitation there, coupled with the role of the permafrost layer, it is difficult for oxygen to enter the rhizome part from the branch of the vegetation, so that the vegetation cannot absorb the nutrients in the soil layer.
Without the rhizomes, the perennial wind will surely blow down the trees that grow here.
2886 hours is even more difficult for their plants, during the day, they can not do well photosynthesis; at night, they urgently need a lot of oxygen to maintain physiological functioning. None of these conditions can be met, so it is difficult for trees to grow here.
In short, the growth of any life needs to have certain conditions, and sometimes it is really indispensable. The extremely special environment of Nagqu County is the main reason why there are no trees for thousands of years.
< h1 class="pgc-h-arrow-right" > concluding remarks</h1>
Trees generally require fertile ground, adequate water, moderate carbon dioxide and oxygen, and plenty of light time. Some people believe that trees are the lungs of the earth, and the earth mainly relies on them to produce oxygen, achieving the free conversion between carbon dioxide and oxygen.
Without them, it is difficult to say whether there will be other life on Earth. 500 million years ago, it was oxygen that promoted the growth of vegetation, and it was also vegetation that continued to increase oxygen levels until today's levels.
The main reasons why the Nagqu county area does not have the ability to plant trees are the presence of permafrost, thin air and excessive rainfall. From here, other scientific research experience can also be summarized, and if these problems are broken, then the cultivated plants serve the human and animal and plant communities.
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Geography of Tibet
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