When a man is killed and a volcano erupts: what can dendrochronologists read from tree rings?

– You recently published studyThanks to the trees, they learned how the climate in Western Siberia has changed over the last 7,000 years. How old are the trees?

– We determine the year of formation, not the age of the ring. We count the age by the number of rings. The fact is that trees of the same species in each region react in the same way to changes in the external environment. For example, everyone’s rings are wide if it’s hot, and narrow if it’s cold. If we take the segments somewhere in 50-100 years, then this pattern of ring variability from year to year is unique. This has been proven empirically.

First we drill holes in live trees with a special drill. Then we take 5 mm thick wooden cores from there and see all the rings on them. In a living tree, we know every year that the ring is formed. If we took a seed from a tree in 2022, the last link will be 2022 and we are just counting the years from it.

Then we find, for example, a tree stump of unknown time when it died. We take a saw cut, measure all the rings and compare the pattern of a living tree with a log. If their lives do cross, the numbers will coincide during this time. This is called cross flirting. As a result, we get a drawing for a longer period, which includes the life of a dead tree.

There are also falling and false rings – in a very cold year it may turn out that the ring forms only in the upper part of the stem and not in the lower part, at the height from which we took the sample. available. Sometimes it turns out that several rings are missing over the years. We do not see them. And in our case, this is very common in the north – in one example there may be 20 falling rings. Again, cross flirting helps such rings to be recognized. If we see that ten trees have a ring and one or two is not enough, it means that the ring simply falls out, especially if these ten trees have narrow ones.

False rings are the formation of a second layer within a year. For example, the conditions deteriorated, the tree stopped growing, then the conditions stabilized again and the growth continued, two rings appeared in one year. But this is rare in the north.

So we can date it to a fairly long period in time – especially in Yamal, the wood is very well preserved in the permafrost. And so we’re constantly expanding the chronology, now we’ve looked back 8,768 years, which is more than the recently published paper. Moreover, we know for certain that we can expand this chronology to 9,100 years next year.

And then – maybe not. There are suspicions that by then there were almost no trees in Yamal.

– How long does it take for trees to tell in general, not just in Yamal?

– The longest chronology today is in Europe. That’s about 12,460 years for Central Europe. But why is our chronology better? Because we work in the north, where trees are climate sensitive and ring width is highly correlated with temperature. There is no such thing in Europe. It is almost impossible to obtain accurate climate information using tree ring widths in these regions.

You are comparing living trees to petrified logs. Does their environment affect their situation and, accordingly, the results of their work?

– It would be more accurate to say semi-fossil, not fossil. Of course, the tree would be rotten, but we also find trees with bark, branches and cones in place.

What are the oldest known trees in the world?

– Annual rings on trees appeared 350-250 million years ago, but it is not possible to determine exactly. Most likely, the rings appeared as coniferous trees appeared.

If we talk about trees used to study tree rings, for example, there is a publication about South America – they found overgrown trees 50 thousand years ago.

– And what are the oldest trees in Russia?

– If we talk about living trees, then colleagues in Yakutia discovered a 945-year-old larch. They also found a tree that died more than a thousand years ago in the same place, and it was 1,216 years old at the time. And in Altai, larch can live up to 1300 years. The oldest woody plant in the Urals is juniper, it has 840 rings.

But in general, the longest-lived trees are the spiny pines, there are many of them in the USA. There, their age reaches almost 5,000 years.

– In addition to studying the climate, what is the data obtained for?

– There are many applications, but 80-90% are related to climate – temperature, precipitation, drought index etc.

Dendrochronology is a traditional way of determining the dates of certain events. For example, other archaeologists at Salekhard found the mummy of a man with a wooden nail in his feet. They came out with this latch – it turned out that the man died in 1282.

Trees make it easy to inform about extreme weather conditions, such as mid-summer frosts, when temperatures can drop below 0 degrees in July. Then an abnormal structure, such as a frost ring, forms, abnormally shaped cells, some die. With an accuracy of a week we can say, for example, in 1627 BC. On July 10, a severe cold occurred.

There is also an interesting connection here – such frosts occur when powerful volcanic eruptions occur. For example, in 1815 there was the eruption of Tambora volcano (Indonesia), in 1600 there was the eruption of Huyanaputina in South America (Peru).

All these events led to severe cooling in the northern hemisphere, which led to famine, especially in Russia in the Time of Troubles. These cold snaps have left their mark on the growth rings of the trees.

Natural events can be dated: avalanches, pest outbreaks reflected in the rings. In order to restore the dynamics of the number of insects, it is possible to determine the frequency of occurrence of these epidemics. There is a lot of work on fires, abnormal rings are also formed after fires.

– How could an explosion have such consequences?

— When the products of the explosion enter the stratosphere, rising to a height of 20-30-40 km, they do not settle immediately, but form a film of sulfate aerosols that reflects light. Because of this, the temperature drops sharply.

— Are there any known discoveries made by dendrochronology?

– Of course! About 10 years ago, Fusa Miyake, a young girl from Nagoya, was studying the rings of Japanese cedars, discovering in 775 that the rings had a huge jump in radiocarbon content. This means that the content of this isotope also increases in the atmosphere. This can only happen in the case of a large flux of cosmic rays.

Miyake suggested that it was a supernova explosion. Physicists later proved that it was a solar flare. It was truly a revelation.

It turns out that sharp bursts of the stream of cosmic rays can be detected from the annual rings. They called it the “Miyake events.”

Of course, its discovery was rechecked, it turned out that in 40 different parts of the world, in the same 775 year, there was a radiocarbon increase of trees. This is surprising, but some scientists from other fields of science have doubted the cross-dating and dendrochronology method in general.

This year, with our participation, an article was published talking about such super-powered solar flares in 7176 BC. and 5259 BC.

— Is it true that dendrochronology is used in forensics and forensics?

“Two people in our lab do this almost all the time. One example is atypical. It was many years ago.

In the Sverdlovsk region, a long decomposed corpse covered with large branches was found. Colleagues studied them and found out in what year the branches were cut. So you can set the crime year.

But most often we are talking about illegal registration. Based on the comparison of the growth ring pattern, we can tell whether the pattern on the log from which the tree was illegally felled matches the pattern on the felled tree on the suspect’s property.

— Could the warming you recorded in Siberia degrade biodiversity?

– Can change, violate – the word is not entirely correct. The climate is really changing, the tundra is disappearing somewhere, various animals are increasing in the north that can migrate much faster than trees. First of all, insects, birds.

– According to a study by scientists from the University of Washington, by 2100 it will be impossible for a person to live in the tropics and subtropics due to extreme heat. Do you agree with this?

I also saw this work. It’s quite possible, why not. I can say for sure that the number of extreme weather events will probably increase, we can observe this already. But generally I don’t guess, they know better.

What research are you doing right now?

– The first technical task is to extend our chronology to 7100 BC, the second is to reconstruct the changes in various climatic parameters over several millennia using the analysis of dendroclimatic, cellular structures and the content of the oxygen-18 isotope. Another direction is the analysis of radiocarbon in the annual rings to describe past super-strong solar flares, the dynamics of solar activity.

As a change, we examine what has happened at the northern border of modern forests over the past 100 years, based on dating not only living trees but also preserved tree remains.