The years of life of trees of temperate and cold latitudes can be determined by the transverse saw cut of their trunks, considering the annual rings (annual layers). Such a layer, as a rule, corresponds to the growth of wood during one growing season. Wood, born in spring and early summer, is markedly different from the later one that appears in late summer and autumn.
When a tree is just beginning to vegetate, then in wood many wide-spaced vessels are formed. In the fall, the vessels are formed narrow, and it becomes more dense and dark. Usually, the transition from early wood to late wood is gradual, but the transition from late wood to early wood can be traced quite clearly, and the boundaries between them are clearly visible to the naked eye. Each ring, as a rule, corresponds to one year. Although sometimes there are so-called false rings. This happens if, due to an unfavorable summer (drought or cold), it begins to veget in the fall.
This was the incident that occurred in Türi (Estonia) on August 25, 1818. During a thunderstorm, lightning struck a 25-meter oak; the affected tree was cut into pieces. And then it turned out that the concentric layers of oak wood under the influence of lightning exfoliated from each other and freely put forth like a telescopic antenna.
The Oldest Giant Trees
Since each year the thickness of the trunk increases, it would seem that long-livers should be sought among thick trees. And, indeed, for a long time the gigantic trees growing in North America were considered the oldest - sequoias and sequoiadendrons.
Sequoias are giant trees: the height is about one hundred meters, the trunk diameter reaches 8.5 m. One such saw was sawed with a seven-meter saw for almost two weeks, and it took 30 railway platforms to transport the wood of this tree. Two more curious facts. In the Sequoia National Park (USA), on the stump of a gigantic sequoia cut in the middle of the 19th century, enterprising Americans staged a summer dance floor, where 16 pairs of dancers, 20 spectators and 4 musicians were placed simultaneously.
In Yosemite National Park (20 km from San Francisco) grows the famous sequoia "wahwonah" - the great conifer tree . In 1881, on the site of a huge hollow, a tunnel 8.7 m long, 2.5 m wide and 3 m high was punched in its trunk.
Even more impressive in size of the sequoiadendron (Wellingtonia, mammoth tree), its trunk diameter reaches 10 m, grows in California on the western slopes of the Sierra Nevada.
Among these giant trees of the plant world, they discovered a sequoia whose age was 2125 years. For a long time it was considered the oldest tree.
Comparatively recently, the palm among the long-lived trees of redwood gave way to a spiny intermountain pine that grows on the rocky slopes of the White Mountain Mountains (west of North America). Nobody assumed that, in general, small trees (up to 10 m high) have such a respectable age. In 1955, one of these pines was cut down for scientific research. When, according to the annual rings, her age was calculated, the scientists were extremely surprised: 4900 years old spiny pine! The researchers had no choice but to blame themselves for indiscretion and regret their deed.
But the rest of the old pine trees were studied with extreme caution and since 1958 taken under state protection. Among the long-lived pines we counted a lot of trees, whose age has exceeded 4 thousand years. All four thousand trees received their own names: “Alpha” - the very first tree found over 4 thousand years old, “Patriarch” - the thickest tree of spinous pines (trunk diameter 3.5 m), “Methuselah” - the oldest living tree, he is 4600 years old (according to biblical tales, Methuselah lived the longest among the people - 969 years).
Annual rings of spinous pine are so dense that they are indistinguishable with the naked eye. This is not surprising: after a hundred years, the diameter of the trunk does not increase by more than 2.5 cm. And in one of the sections of the slice, only 12 cm long, it counted 1,100 annual rings. So the most ancient of the spinous pines appeared on Earth when the pharaohs in Egypt began building the first pyramids.
The annual rings determine not only the age of the tree
Today, to determine the age of a tree, there is no need to cut it. Dendrochronologists, specialists in “reading” growth rings, drill down wood pillars as thick as slate, and then examine them under a microscope.
And Japanese inventors designed a portable X-ray machine, with which you can take pictures of the diameter of the trunk, without causing even the slightest harm to the tree; According to these images, the specialists determine not only the age of the tree, but also its state of health (how much this word can be applied to the tree).
The width of tree rings varies from year to year, so the totality of all rings is a chronicle in which a connoisseur can read everything: temperature fluctuations of air, rainfall, forest fires, the invasion of pests, the death of neighboring trees. The width of each individual ring is also not the same everywhere; it depends on the position of the tree relative to the sun, its shading by its neighboring trees, on the direction of the winds, and the like.
Do I need to decipher the wood record? Of course it is necessary, because it helps to reveal some secrets of the past. For a long time, American historians were worried about the mystery of a rocky city built in the 13th century. in Mesa Verde (California, USA). Why did the residents leave it? As told annual rings of logs, without which, of course, did not do the buildings of the ancient city, it happened because of the many years of drought.
Leonardo da Vinci first proposed the age of trees by annual rings ; He also suggested that their width depends on the climate. The connection between the growth of annual rings and meteorological factors — air temperature and precipitation — was first pointed out by Russian scientists A.N. Beketov and F.N. Shvedov in the second half of the 19th century. American researchers from the dendrochronological laboratory of the University of Arizona established the annual layers of spinous pine in western North America in 1453, 1601, 1884, 1902, 1941 and 1965. the summer was abnormally cold. Data for 1941 and 1965 coincide with observations of meteorologists. The fact is that in years with a cold summer, the activity of the cambium (the connective tissue that generates wood) is weak. Damage to wood cells formed during the summer indicates an invasion of cold air masses.
So, exploring the annual rings of spinous pines and preserved fragments of dead wood of these trees, American scientists have compiled a consolidated climate calendar of the west. 
North America, where up to 6200 BC. er characterized every year.
Similar studies were carried out in the former Soviet Union. At the Botanical Institute of the Academy of Sciences of Lithuania, there used to be a dendroclimatochronological laboratory. In it, they created a dendroscale covering 900 years. On the rings of the old cedar Scientists discovered in Altai, the scientists found out what the climate was in these places from 1020 to 1979. The cedar dendroscale clearly shows how 11-year cycles of solar activity affect the climate. And we also noticed 80-90-year-old rhythms, the cause of which has not yet been finally determined.
And in the journal “Nature” for 1976, a message appeared on a new method for determining the climate of past centuries by annual rings. It is established that the ratio of carbon, oxygen and hydrogen isotopes in the earth's atmosphere depends on its temperature. So, having calculated the isotopic composition of each ring of wood, it is possible to calculate the average annual temperatures of the ages past. Only for this it is necessary to establish a quantitative relationship between the isotopic composition of the annual layers and the known average annual temperature.
Scientists from England, Germany, and the USA worked on the creation of a tree thermometer. They conducted their research in England, where they began to record the temperature of the environment, about 300 years ago. Not far from the temperature registration sites, ancient oaks and fir trees and analyzed the content of isotopes in the rings. So graduated scale wood thermometer. The study of old-timers trees helped to find out what the weather was several centuries ago, when they even had no idea that heat and cold could be measured.
But not only about the climate of past centuries can tell the annual rings coniferous plants . American scientists have found that large volcanic eruptions are recorded in them. Indeed, during the eruption, a large mass of volcanic ash and dust is emitted into the upper atmosphere, which can remain in the atmosphere for two to three years. The smallest solid particles trap the sun's rays, so it gets colder on the ground.
Exploring the spinous pine, scientists confirmed the eruption of Mount Etna in 44 g. er Only this eruption was recorded in tree rings in 42 g. er .: it took two years to drive a cloud of volcanic dust and ash from Sicily to America.
The date of the eruption of Etna is well known to scientists, but about another major eruption of the Santorin volcano, which destroyed the Minoan culture on about. Crete, historians had a dispute. Some believed that the eruption of the Santorin volcano was between 1700 and 1450. n e., others - between 1500 and 1300 BC er According to the annual rings of the spinous pines, dendrochronologists established that the eruption of the Santorin volcano occurred between 1628 and 1626. BC er
About ten years ago, an American botanist, A. G. Dzheikobi, suggested that the tree rings growing in areas with seismic activity could be determined when an earthquake occurred and even how strong it was.
In his reasoning, it is based on the fact that an earthquake usually changes the conditions in which the forest grew: the root system is damaged, the supply of trees with groundwater changes, and so on. Naturally, these factors affect the growth of the tree and should be recorded in tree rings. Indeed, earthquakes are marked by dark rings extended on one side.
Soviet scientist N. V. Lovelius suggested that the rings of old-timers trees should contain information about supernova explosions in the galaxy. He studied the cuts of two such trees: archa (juniper tree) and Amur larch . When they calculated the annual layers of the juniper found high in the mountains of Central Asia, it became clear that this plant was born in 1163 and lived for 807 years. During this time, three explosions of supernovae occurred - in 1572, 1604, 1700. and these explosions had an impact on the Earth’s biosphere. The supernova explosion slowed down the growth of trees: moreover, the oppression reached a maximum at 15-16 years after the explosion, 30 years later the growth returned to normal at the trees. What physiological processes are violated under the influence of a supernova explosion have not yet been established.
Reading the annals of the rings, you can extract and other information. For example, trees can tell about the degree of air pollution in different years. American physicists on the annual rings determine the effects of nuclear testing. Chemists, analyzing the chemical composition of annual rings, study the distribution of scattered elements in different periods.
Each time, after re-reading our favorite book once again, we find something new for ourselves in it that we hadn’t noticed before. So with the annals of annual layers: years will pass and maybe someone will read it in a new way and open for us a completely different content of this wooden chronicle, written by Nature.
V. Petrishin
Do I need to decipher the wood record?Why did the residents leave it?
