When walking through the forest and noticing an old stump, an inquisitive person will certainly stop and pay attention to the mossy cut of the tree. What does he remember? What would you say if you had a voice? Having erased the cover of moss from the cut, it is easy to notice circles crossed out by cracks. Tree rings can tell a lot. About the youth of the plant, about its life cycle, about cold cold and hot dry days. Before the eyes of knowledgeable people, year after year, decade after decade, is revealed. This science was born recently, it is called dendrochronology.
The concept of dendrochronology
Studying cross sections is not difficult. A cut of a tree is examined under a microscope, each annual layer is measured in millimeters. According to the measurements, a special graph is drawn up, it indicates the change in the thickness of the rings. The graph creeps up if the thickness of the rings is wider (favorable years for the tree), the graph decreases when the years were dry, difficult. After analyzing the fresh saw cut of a tree, and building a graph, you can get a chronicle of his life, indicating the weather conditions for the period of the life of this plant, that is, the last years of our time. Having found a cut of an ancient tree in the forest, you need to do the same work and getschedule. It will be possible to judge the weather conditions of the period in which it grew. So year after year you can delve into history.
But not everything is so simple. In European forests, ancient trees do not survive more than three or four hundred years, except that the oak sometimes lives up to half a millennium. But it is very difficult to study a cut of a hardwood tree. Vague rings reveal secrets rather reluctantly. American scientists were in a more advantageous position. There, some trees have lived life for a whole millennium. These are some gymnosperms, yellow pine, Douglas fir. Alpine pines have even been discovered that have lived for four and a half thousand years. During excavations at the site of the dwelling of the Indians, saw cuts were found, according to which it was possible to compile dendrochronological graphs for the whole millennium.
Annual rings. Research in Russia
For many years, scientists have studied only the wood of America. Europe turned out to be a blank spot in this area. Only after the war in Russia did scientists start looking for ancient saw cuts. The northern regions turned out to be favorable for research. The soils here are well moistened, and the frozen soil has perfectly preserved many tree trunks. Scientists collected a huge "harvest" of wood during excavations in ancient Novgorod. Several thousand of various rocks were found here, layered on top of each other at different depths. Layer by layer, scientists unearthed archaeological material: risers of churches, log decks, log cabins of wells. The finds were found at a depth of eight meters. But how couldlink the age of disparate finds? Sections of the tree trunk were prepared from more than three thousand specimens. Each breed had to build its own dendrochronological scale.
Dendrochronologists have done a tremendous job. They didn't just make charts. To establish a reference schedule, I had to study the entire history of the ancient city, chronicles, and determine in what year this or that wooden structure was erected.
Aegean Dendrochronology Project
The high-profile Aegean dendrochronological project has been in progress for 35 years. Its goal is to create an absolute dendroscale for the Middle East and Aegean regions, inclusive, from trees of the first millennia BC to modern exhibits. The work is carried out by scientists at Cornell University in the USA. Main results of the project:
- The absolute dendroscales for such species as oak, cedar, juniper, pine were made. Their period is calculated up to 750 BC.
- Completed construction of the floating Aegean dendroscale with an accuracy of 2657-649 BC (by juniper).
- Also, a cut of a tree on a juniper helped to build a floating dendroscale for the period 2030-980 BC. The results were published in 2005.
- Known issues have been identified for the Roman Gap and the EVE problem.
The achievements of American scientists are still considered controversial, as the probability of error in some cases is from 100 to 200 years.
Research in Finland
Northern Finland has become one of the suitable areas for research. In these places there is a line of climatic boundary. Professor Jan Esper claims that sunken shafts retain all the information for hundreds of years. So, a small cut on a tree lying in a cold lake will tell a lot. In the north of Finland there are many such lakes that store invaluable information. Dendrochronologists claim to be able to unravel the mysteries of climate in two thousand years. Using a special drill, laboratory workers manually extracted samples of tree rings. Then they were examined under a microscope using computer technology. The compiled dendrochronological graphs helped to recognize how the climate changed and even when volcanic eruptions occurred on the territory.
Climate change
According to the data obtained, scientists were able to establish that the average temperature on the planet dropped by 0.3 degrees every millennium. This continued until the beginning of the twentieth century - the Industrial World Revolution. The development of scientific and technological progress has led to the fact that the amount of greenhouse gases on Earth has increased significantly. Dendrochronologists have not studied this period in detail.
During the time of the Roman gladiators, the climate on the planet was much warmer. The “warm phase” can also be called the Middle Ages. Then came the cooling, which continued every year until 1900. Our modern man, on the contrary, is now concerned about global warming. As you can see, even a small cut of a tree branch can tell a lot. Unfortunately, with the onset of the greenhouse effect, with the conditions in which the atmosphere is polluted and the climate depends, in some way, on human activities, dendrochronology data can only indicate temperature fluctuations.
