83.4 meters, the life-size photo of "China's tallest tree" released! How was it measured?

On October 9, the Chinese Giant Tree Expedition Team announced the exact height of "China's tallest tree," Abies huangguoensis in Yunnan, at 83.4 meters, and also released a life-size photo of the giant tree. What kind of tree is this? How is it measured? Is there a taller tree?

Compiled by reporter Fang Yongzhen New media editor: Lv Bingxin

October 9

The Institute of Botany, Chinese Academy of Sciences

China Giant Tree Expedition Team

Release of the current "China's tallest tree"

The exact height of Abies yunnanensis is 83.4 meters

At the same time, a life-size photo of the giant tree was released

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▲The life-size photo of the giant tree was completed by stitching together more than 160 photos. The overall frame of the photo exceeds 350 million pixels and can be projected onto a 100-meter giant screen to show the details of the giant tree.

Trees over 70 meters tall

Scientists call it a giant tree

China's giant tree is 83.4 meters high, equivalent to a 28-story building

The expedition team also created

New records of climbing and collecting giant trees in China

▲Giant tree communities along the banks of the Zayu River (Photography and synthesis/Wild China studio team)

In May this year, the Institute of Botany of the Chinese Academy of Sciences discovered the tallest tree in China to date during an investigation in Tibet - the 83.4-meter-high Yunnan yellow fruit fir, which grows in Zayu County, Tibet.

This newly discovered "king tree" not only breaks the record for the tallest tree in mainland China, but is also taller than the 82-meter Taiwania baldness in Taiwan Province, China. What kind of tree is this? How is it measured? Is there a taller tree?

What kind of tree is this and how was it discovered?

Yunnan yellow fruit fir is a variant of yellow fruit fir. The main difference from the original species is that the needles are slightly thicker and usually longer. Although it is called fir, Yunnan yellow fruit fir is not a true fir tree. It is a member of the genus Abies in the Pinaceae family and is mainly distributed in northwest Yunnan and southeast Tibet in my country.

Abies yunnanensis grows in areas with a mild climate and an altitude of 2,600-3,600 meters. The mountains and valleys with brown forest soil are their favorite living environment. Abies yunnanensis usually forms a mixed coniferous and broad-leaved forest with conifers and broad-leaved trees such as Pinus armandii, Taxus chinensis, Fraxinus chinensis, and Populus chinensis. In the forest, Abies yunnanensis, which is an average of 60 meters tall, is usually a top-story tree species, towering over other plants.

The newly discovered Abies yunnanensis forest is distributed in a belt-like pattern in the mountains and valleys on both sides of the Chayu River in Shangchayu Town, Chayu County, Tibet, at an altitude of about 2,300 meters. The community contains a large number of ancient yew trees, a national first-class key protected wild plant, as well as epiphytic plants such as orchids and ferns.

How is it measured?

How high is 83.4 meters? The height of a floor is about 2.8 meters, which means that this Chinese "king of trees" is close to the height of a 30-story building.

It is understood that this scientific expedition used the international "gold standard" for measuring giant trees - the tree climbing direct measurement method . That is, after manually climbing to the top of the giant tree to determine the highest treetop, a metal tape measure was lowered from the treetop to the ground for measurement.

▲Scientific expedition team members measuring on the treetop

Because the tree is huge and located on a slope, the lowest point in the center of the trunk cannot be reached. The expedition team conducted multiple measurements and found that the height difference between the exposed part of the inclined stump was 0.8 meters. After determining the location of the center point of the stump, it was finally concluded that the height difference from the lowest point in the center of the trunk to the treetop was 83.4 meters.

In addition to measuring with a ruler, lidar measurement is also very practical.

▲The laser radar system carried by researchers (Source: Science and Technology Daily)

The LiDAR tool sounds mysterious, but its working principle is actually very simple. It uses laser to measure the distance between two points. The distance data between the earth and the moon is also measured by laser.

Experts said that LiDAR is an active remote sensing technology that can directly, quickly and accurately obtain a three-dimensional point cloud model of the research object. By measuring the position and distance of multiple points in space and processing these data with a computer, a 3D mapping data model of the area where the tree is located is finally established. In this way, it becomes very easy to accurately calculate the height of the tree.

▲UAV used for measurement (Source: Science and Technology Daily)

When measuring the Yunnan Abies, we have used the drone rope method for many measurements. We use the drone to fly to the top of the tree crown, lower the rope, and then measure the length of the rope. The use of drones can ensure that the rope is vertically taut, which more accurately reflects the true height of the tree.

The tree's height is related to its growth environment

It is extremely rare for trees to grow so high. It is almost impossible for such tall trees to appear in plains because strong winds and lightning do not allow trees to grow so high.

There is an old saying that goes, "A tree that stands out in the forest will be destroyed by the wind." If a tree grows too tall, it will be difficult for it to withstand strong winds. Also, lightning in thunderstorms is most likely to choose taller trees or buildings to release the electric current in the clouds. Therefore, trees will not grow too tall in places where strong winds and lightning are likely to visit. Therefore, the 83.4-meter-high giant tree discovered in Zayu County, Tibet, and the 76.8-meter-high giant tree discovered in Medog County, Tibet, both have their own special growth environment, that is, they are both located in valleys or river valleys.

The terrain in which these tall trees grow is relatively low, and there are tall mountains around them that can block strong winds and attract lightning currents. This protects the growth of trees in the valley very well and makes them tall.

"The reason why this area has been able to preserve such tall and intact virgin forests is due to the superior climate and terrain conditions, as well as very little interference from human activities. The large number of tall trees here and their communities and ecosystems have important scientific research value and conservation significance," said Guo Ke, a researcher at the Institute of Botany, Chinese Academy of Sciences.

These virgin forests in Medog County and Zayu County in Tibet are all south of the Himalayas. The altitude gradually decreases from north to south, and the vegetation types are becoming more and more abundant. However, the mountains are crisscrossed by rivers and valleys, and the terrain is very complex. There are many tall trees, and perhaps there are taller trees that have not yet been discovered.

How far is China's tree king from becoming the world's largest?

Although it reaches a height of 83.4 meters, it is still some distance away from the World Tree King.

First, let’s take a look at the more famous General Lehman Tree. The Yunnan yellow fruit fir discovered this time is of comparable height to the famous General Lehman Tree, which is about 83.8 meters tall. However, it is thicker. The maximum diameter at the base of the General Lehman Tree is 11.1 meters. The diameter at breast height of the newly discovered tree king in my country is 2.07 meters.

▲General Lehman Trees. People seem so small under these giant trees. (Image source: Science Black Hole)

Of course, General Lehman tree is not the thickest tree. The thickest tree must be the baobab tree. The thickest baobab tree discovered so far has a base diameter of about 28 meters.

The tallest trees in the world are redwoods and eucalyptus almonds. For example, Hyperion in Redwood National Park in California, USA, is 115.2 meters tall, and the top ten redwoods in the world are almost all over 110 meters tall. The largest eucalyptus almond is located in Tasmania, Australia, and is about 100 meters tall.

▲A large number of redwood trees in Sequoia National Park in California, USA (Photo source: Science World)

Therefore, the newly discovered 83.4-meter-tall tree king in my country is about 32 meters away from the tallest tree in the world.

The height seems so weak to describe with numbers. In comparison, it is 20 meters taller than London's Big Ben or New York's Statue of Liberty. Just look at the comparison picture below to see how tall it is.

(Photo source: Science World)

Why is it difficult for giant trees to exceed 120 meters?

Since the discovery of Hyperion, the world's tallest tree in 2006, the location of the world's tallest tree has not changed. Some people say that 120 meters is a huge hurdle that trees can hardly break through.

From a biological point of view, the taller the trees grow, the better it is for them to grab enough sunlight for photosynthesis in the dense forest. However, if they grow too high, there is a huge obstacle, which is that it is difficult to transport nutrients to the top. We know that one atmosphere of pressure is equivalent to the water pressure at a height of 10 meters. If you want to press the water up to 120 meters, it is equivalent to providing 12 atmospheres of pressure. You can imagine how difficult this is. Obviously, the water needed by plants is not pressed up, but mainly through two ways - capillary action and transpiration.

(Source: Scientific World)

There are a large number of tiny channels inside the tree. The inner walls of the channels are hydrophilic. When the water on the leaves continues to evaporate, the water will generate tension under the action of the inner walls, thereby forming an adsorption effect. In addition, hydrogen bonds can also be formed between water molecules. The resulting adhesion force can help the water molecules overcome gravity and transport upward.

(Source: Scientific World)

However, if the tree grows too high, the water evaporates too quickly, and it is difficult to balance the water transport and evaporation, and the plant is prone to water shortage. In addition, tall trees may not necessarily have an advantage in resisting bad weather, so this height is also the result of natural selection.

The record-breaking tree discovered this time is of great value and significance for our study of plant physiology, especially the physiology of water and nutrient transport.

(The content of this article is compiled from the Institute of Botany, Chinese Academy of Sciences, CCTV News, Science Popularization China, Science World, Science Popularization World, Global Science Cat, etc.)