How many years per ring on a tree

Do Tree Rings Really Indicate Age?

Have you ever come across an old tree stump and started counting the rings? The adage says the tree rings indicate how old a tree is, but is that really true?

Those tree rings tell you how old a tree is, and more.

Trees are nature’s environment log books. They can live hundreds or thousands of years. Every year brings on new circumstances and experiences. And as a tree survives all that nature throws at it for the year, it records in the growth rings of the tree.

Dendrochronology is the science of studying these experiences. It works to date events and environmental changes through the study of tree rings.  Scientists have been studying tree rings for centuries and have used that data to learn more about climate, atmospheric changes, and the local geography.

These growth rings indicate the age of the tree, plus they leave clues to help you understand the climate conditions the tree lived through.

What is a Tree Ring?

When you look at a tree stump, you may see that the top of a trunk has a series of rings. It starts with one small ring in the middle followed by a continuum of circles with each circle encompassing the one before it.  

The center circle indicates the first year of growth. Each ring afterward indicates another year as well as the climate condition of that time. These growth rings grow under the bark, and the bark is pushed out while the tree grows.

Tree rings are created because trees manufacture new cells every year. These growth layers act as a timeline of a detailed report on its growth throughout its time. Trees learn to survive with the different climate conditions, and the tree rings help us understand how.

Tree Rings Indicate Age of the Tree  

In the United States, the tree-growing season starts in the spring. When you look at a tree sample, this season is shown by light-colored, pale wood. Growth slows down at the end of summer, which creates smaller walls and darker colored wood.

A one-year cycle is comprised of a light pale wood that grew at the start of the year and a dark wood that grew at the end of the year. When a tree is cut, you will notice alternating light and dark wood rings. Count the dark rings, and you will get the tree’s age.

Fortunately, you don’t have to cut a tree down to study its growth rings. A boring tool is used to get a tree sample to analyze tree rings. It excretes sections of wood by screwing into a tree to get a straight, unbroken sample of the core. It is a T-shaped tool, and the professional tree service company you work with will have these on hand.

Your arborist in Portland can take the sample.  They will know how to cover up the hole from the sample excretion to keep the tree alive. They will also be able to identify the dead trees to work with and avoid damaging healthy ones.

Count the tree rings, and you will find some trees have up to thousands of rings. Examine more closely, and you will see different shapes, sizes, consistencies and gaps which indicate the conditions the tree lived through.

Tree Rings Indicate Environmental History

A typical tree will have tree rings with different variations that signify its life story. The layered growth indicates the climate conditions such as drought, fire, insect attack, flood and many more natural disasters that we wouldn’t have been able to trace by ourselves.

Variation of tree rings occurs because of the different conditions each tree faces. Trees are sensitive to climate, which is why they help indicate the environmental condition at a certain time.  That’s why it’s always a good idea to take samples from more than one tree to compare and eliminate individual variations.

If it’s a difficult year, a tree produces a thin ring signaling slow growth. This indicates a cold and dry year. When it has positive-growth conditions, a thick ring is produced because of the added tissue the tree produces for fast growth. A thick ring indicates a warmer wet year with abundant rainfall. Consistent tree rings signify a consistent climate throughout those years.

Thin rings may also occur because of overcrowding of trees, which limit the tree’s growth.  Trees that have plenty of space to grow straight at a rapid pace will have wide, evenly spaced rings.

Narrow rings for several seasons can also indicate drought because of the lack of water over a long period of time.

Insect defoliation also creates narrow rings. Each kind of insect will leave different traces of its presence, and this can help understand insect productivity and infestation.

Narrow rings also indicate forest fire damage. When trees are injured they develop boundaries around the tissue to prevent infestation. If the tree lives on, the tissue becomes the new layers of wood around a tree trunk. A damaged bark and exterior is a forest scar.  While forest scars vary based on species, they all result in narrow rings due to the discouragement of growth.

Tree rings that are wider on one side mean that something was pushed against the tree while it was growing. The tree starts to lean because it produces wood to react to the other subjects.

Since trees can live thousands of years, scientists use trees to determine the events of the past. While there are new trees constantly being planted, scientists can focus on old trees to get a clue of what the climate was like even before the measurement was being recorded.

Through tree rings, we can understand the occurrences of natural events, and this can help us understand the future of potential environmental circumstances.

While we can’t control the weather, our pros at Mr. Tree can offer planting and care for your trees to ensure a long and healthy life. As arborists in Portland, we use environmentally friendly practices and a holistic approach to ensure all aspects of your landscaping will thrive. To find out what other professional services are offered, visit

Dendrochronology – Determining the Age of a Tree – Tree Removal

By providing shade from the heat of the sun, giving us wood products, and turning carbon dioxide into oxygen, trees play an important role in our society and the Earth’s ecosystem. From the beginning of history, we have relied on trees of various types to meet our needs. Much can be learned about a species of tree and its environment by discovering its age, and researchers employ several methods to date trees.

Tree-Ring Dating

The most common, most accurate way to find the age of a tree is to count the number of rings visible when their trunk is cut horizontally. Each year, most trees add an extra layer of growth to their trunks. Over time, their trunks get thicker and thicker. As the tree gets older, the inside of the trunk looks like it is made up of a series of circles. The center of these circles, or the absolute core of the tree, is known as the pith. Since each ring corresponds to roughly one year of growth, making it possible to get a highly accurate estimate of a tree’s age. This use of tree-ring dating to find the age of a tree is also known as dendrochronology. Researchers can also learn about what a tree endured during a particular year by the condition of the ring they are studying.

Counting the Rings

There are two possible ways to access the rings of a tree so that they can be counted. First, one may simply cut down the tree itself. Of course, this will kill the tree, so it is not recommended as a method for tree dating unless the tree is already dead or if there is no other way of accessing the information. The second method of accessing the rings of a tree for counting is to take a core sample of the tree trunk. To take a sample, researchers use a tool called an increment borer that takes only a portion of the trunk measured from the pith to the bark of the tree. This method of sampling is less harmful to the tree, but taking part of the tree core does run the risk of injuring the tree. Pests, the natural elements, and other things can also invade the core of the tree after a core sample is taken and harm the trunk. Taking core samples at a point in the year where pests and rain are less likely to be present can help lessen some of this risk. Once the core sample is obtained, the tree’s age is determined by counting the number of rings evident in the sample.

Dating Trees without Rings & Different Methods of Dating

The tree-ring dating method works well for most trees; however, it cannot be used to find the age of all trees. That is because some trees don’t have rings or they have rings that are very hard to discern from a trunk cross section or sample. Trees that cannot be dated using the tree-ring method include some species of palm trees, as well as certain trees that grow in desert conditions. These types of trees are known as monocots, and their age is determined mainly by comparing them with other plants. For example, a palm tree can be compared with another tree whose age is known in order to get an estimate of the palm’s age. Radiocarbon dating has also proven useful in dating these trees.

Although cutting into and counting the rings of a tree is one of the best ways to determine its age, it is possible to get a good estimate of a tree’s age without cutting into it. First, measure the diameter of the tree at a point 54 inches from the ground. This can be done by wrapping a tape measure around the tree to find it’s circumference and then dividing that number by 3.14. Multiply the result by the growth factor for that tree species as given by the International Society of Arboriculture.

  • What is Dendrochronology?
  • Age of the Giant Sequoias
  • Dendrochronology: What Tree Rings Tell Us About Past and Present
  • Forest Academy: Annual Growth Rings
  • Gymnosperm Database: How Old Is That Tree?
  • Tree Species and Their Growth Factors
  • How Old Is Your Tree?
  • Royal Forestry Society: Tree Age
  • Tree Coring
  • Tree Growth Study
  • Tree Rings: Methods of Ecosystem Analysis
  • Tree Species Unsuitable for Tree-Ring Dating
  • Tree Talk: Estimating Tree Age
  • Treetures: Ringaling
  • USDA: How Old Is This Tree?

Rings on a tree how old


  • 1 Age of a tree
  • 2 How to determine the age?
  • 3 Tree rings
  • 4 Age rings
  • 5 Contents
  • 6 Plants [ edit | edit code]
    • 6. 1 Ring widths [edit | edit code]
    • 6.2 False rings [edit | edit code]
  • 7 Animals [edit | edit code]
    • 7.1 Oldest giant trees
    • 7.2 Tree rings determine not only the age of a tree

The age of a tree

According to scientists, some trees on the planet live more than 4500 years. They are witnesses to the events that have taken place on Earth for 45 centuries. Of course, not everyone lives to such advanced years. Experts say that the average lifespan of vegetation in the forest reaches 130 years. This largely depends on the conditions in which the forest dwellers are.

How to determine the age?

It is not determined out of curiosity. Often this is a necessary procedure in cases where a decision is made to cut or carry out vaccination procedures.

There are various methods:

  • whorls (fan-shaped processes on the trunk) are counted in coniferous trees. Years are added to the obtained value: for spruce 7mdash; 3, for fir - 5, for cedar - 10;
  • Knowing the average annual growth of a certain type of green space in your area, you need to measure the circumference of the trunk at a level of 1. 3 meters from the ground, calculate the diameter and divide it by the growth factor.

A more accurate way is to count the annual rings inside the trunk.

Tree rings

In places where there is a periodic change in climate, circles appear in the trunk of trees. The process occurs due to the cambium located under the bark. These are living cells that provide growth through their division.

The plant is dormant in winter. Life processes in it are inactive. Violent activity is activated in the spring and continues all summer. At this time, the cambium forms many new cells, and the color of summer is significantly different from the color of spring. As a result, a thin light and a wider dark stripe appears inside the trunk.

Dark circles are growth rings. In some tree species, they stand out more clearly, in others they are barely visible. Their thickness depends on the conditions in which the plant was located.

Determining the age by annual rings

Determine how old a tree can be by the circles on the cut at the base of its trunk or on the stump remaining from it. Ideally, plants form one ring per year. However, natural negative factors can contribute to the appearance of several rings or their absence in one year. If they are not clearly expressed, it is necessary to apply an aniline solution, blue or diluted ink to the cut.

A less radical way to do without a saw cut is to use a Pressler drill.

Its length should approximately correspond to the diameter of the tree. The process does not require cutting:

  • hold the tool at chest level;
  • screw it into the barrel to the core;
  • we take out the sample and count the number of dark bands on it.

After the experiment, the tree needs a small healing procedure to cover up the drilled hole.

Annual rings , also annual rings , annual layers [1] — areas of cyclic growth of tissues in some species of plants, fungi and animals, due to the uneven development of the organism.

The science of dendrochronology deals with the study and analysis of annual rings of trees.


Plants [edit | edit code]

The age of the tree is judged by the number of rings on the cut. In exceptional cases, the number of rings may not match the actual age.

Temperate climates lead to easily separable rings, while in the tropics they are indistinguishable [ refine ] .

Each ring consists of two parts.

In the first half of the growing season (spring), more conductive tissue is deposited (thin [2] , loose, inside), and in the second (summer and autumn) - mechanical (thick [2] , hard, outside).

Tropical plants (eg dragon tree) do not form growth rings, as they grow all year round.

Ring widths [edit | edit code]

The width of each ring may indirectly indicate the climate of that time.

The following regularities have been established:

from the taxon gradually expand with age, then - narrow from the origin from the ancestors - wide layers; from seeds - develops narrow layers from fruiting narrowing of the rings up to 2 times from lighting in a well-lit tree, the rings are wide on the sunny sides, and in a dense forest - relatively narrow; for a tree on the outskirts of the forest, it is possible to determine its direction to the forest in the direction of narrow rings from latitude and height in the far north or high mountains - narrow rings from soil and climate unfavorable conditions thin the rings

The width of the rings sets the nature of the future felling

False rings [ edit | edit code]

Animals [edit | edit code ]

Animal growth rings are also observed in those tissues and skeletal structures that grow continuously but are subject to temperature fluctuations as the seasons change. These include fish scales, mollusk shells, horns and beaks of various animals, flat bones of the skulls of amphibians, reptiles and fish, claws, thin bones of mammals and birds, teeth and fins of some fish [1] .

The years of life of trees in temperate and cold latitudes can be determined by the cross cut of their trunks, counting annual rings (annual layers). Such a layer, as a rule, corresponds to the growth of wood in one growing season. The wood that is born in spring and early summer differs markedly from the later wood that appears in late summer and autumn.

When a tree is just beginning to vegetate, a lot of wide-lumen vessels form in the wood. In autumn, the vessels form narrow, and it becomes denser and darker. Usually the transition from early to late wood is gradual, but the transition from late to early can be traced quite clearly, and the boundaries between them are clearly visible to the naked eye. Each ring usually 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 vegetate in the fall.

This is what happened 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, peeled off from each other and freely moved forward like a telescopic antenna.

The oldest giant trees

Since the thickness of the trunk increases every year, it would seem that centenarians should be looked for among thick trees. And, indeed, for a long time, the giant trees growing in North America were considered the oldest - sequoias and sequoiadendrons.

Sequoias - giant trees: height - about a hundred meters, trunk diameter reaches 8.5 m. One such sequoia was sawn with a seven-meter saw for almost two weeks, and it took 30 railway platforms to transport the wood of this tree. Two more interesting facts. In the Sequoia National Park (USA), on the stump of a gigantic sequoia cut down in the middle of the 19th century, enterprising Americans set up a summer dance floor, where 16 pairs of dancers, 20 spectators and 4 musicians were placed at the same time.

In Yosemite National Park (20 km from San Francisco), the famous sequoia "wahvonah" - a great coniferous tree - grows. In 1881, in place of a huge hollow in its trunk, a tunnel 8.7 m long, 2.5 m wide and 3 m high was pierced. , 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.

Relatively recently, sequoia yielded the palm among long-lived trees to intermountain spiny pine, which grows on the rocky slopes of the White Mountains (western North America). No one imagined 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 growth rings, its age was calculated, the scientists were extremely surprised: the spiny pine is 4900 years old! The researchers had no choice but to blame themselves for their indiscretion and regret what they had done.

On the other hand, the rest of the old-timer pines were studied with extreme caution and since 1958 they have been taken under state protection. Among the long-lived pines, many trees were counted, whose age has exceeded 4 thousand years. All four-thousander trees received their own names: "Alpha" - the very first discovered tree over 4 thousand years old, "Patriarch" - the thickest tree of spined pines (trunk diameter 3.5 m), "Methuselah" - the oldest living tree, he is 4600 years old (according to biblical legends, Methuselah lived the longest among people - 969 years).

The growth rings of the bristlecone pine are so dense that they are not visible to the naked eye. This is not surprising: after all, in a hundred years, the diameter of the trunk increases by no more than 2.5 cm. And in one of the sections of the cut, only 12 cm long, 1,100 growth rings were counted. So the oldest of the spiny pines appeared on Earth when the pharaohs began to build the first pyramids in Egypt.

Tree rings do not only determine the age of a tree

Today, to determine the age of a tree, there is no need to cut it down. Dendrochronologists, experts in "reading" growth rings, drill slate-thick wood with a gimlet and then examine them under a microscope.

And Japanese inventors have designed a portable X-ray machine that can take pictures of the diameter of the trunk without causing even the slightest harm to the tree; according to these pictures, experts determine not only the age of the tree, but also its well-being (as far as this word can be applied to the tree).

The width of the growth rings of a tree varies from year to year, so the totality of all the rings is a chronicle in which a connoisseur can read everything: temperature fluctuations in the 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 neighboring trees, on the direction of the winds, and the like.

Is it necessary to decipher the tree 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 the rock city built in the 13th century. in Mesa Verde (USA, California). Why did the inhabitants leave it? As the growth rings of logs, without which, of course, the constructions of the ancient city could not do, told, this happened due to many years of drought.

Determine the age of trees by annual rings was first proposed by Leonardo da Vinci; he also suggested that their width depends on the climate. The relationship 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 from the annual layers of spiny pine that in the west of North America in 1453, 1601, 1884, 1902, 1941 and 1965 the summer was abnormally cold. Data for 1941 and 1965 coincide with the observations of meteorologists. The fact is that in years with cold summers, the activity of the cambium (the connective tissue that gives rise to wood) is weak. Damage to wood cells formed in summer indicates the intrusion of cold air masses.

Thus, studying the growth rings of spiny pines and the remaining fragments of the dead wood of these trees, American scientists compiled a consolidated climatic calendar in the west of North America, where up to 6200 BC. e. characterized each year.

Similar studies were carried out in the former Soviet Union. There used to be a dendroclimatochronological laboratory at the Botanical Institute of the Lithuanian Academy of Sciences. In it, they created a dendroscale covering 900 years. Using the rings of the old cedar found in Altai, scientists have established 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. They also noticed 80-90-year-old rhythms, the cause of which has not yet been finally clarified.

And in the journal "Nature" for 1976, a report appeared on a new method for determining the climate of past centuries from tree rings. It has been established that the ratio of carbon, oxygen and hydrogen isotopes in the earth's atmosphere depends on its temperature. So, by calculating the isotopic composition of each ring of wood, one can calculate the average annual temperatures of bygone years. 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, USA worked on the creation of a wood thermometer. They conducted their research in England, where they began to register the ambient temperature for the first time - about 300 years ago. Ancient oaks and fir trees were investigated near the places where temperatures were recorded and the content of isotopes in the rings was analyzed. This is how the wood thermometer scale was calibrated. The study of old-timer trees helped to find out what the weather was like several centuries ago, when they had no idea that heat and cold could be measured.

But the annual rings of coniferous plants can tell not only about the climate of the past centuries. American scientists have found that they also recorded large volcanic eruptions. Indeed, during an eruption, a large mass of volcanic ash and dust is ejected 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 earth.

Examining the bristlecone pines, scientists confirmed the eruption of Mount Etna in 44 BC. e. Only this eruption was recorded in the growth rings of trees in 42 BC. e .: 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 Santorini volcano, which destroyed the Minoan culture on the island. Crete, historians had a dispute. Some believed that the eruption of the Santorini volcano was between 1700 and 1450. n. e., others - between 1500 and 1300. BC e. According to the growth rings of bristlecone pines, dendrochronologists have established that the eruption of the Santorini volcano occurred between 1628 and 1626. BC e.

About ten years ago, the American botanist A. G. Jaikobee suggested that the growth rings of trees growing in areas with seismic activity can determine when an earthquake occurred and even how strong it was.

His reasoning is based on the fact that an earthquake usually changes the conditions in which a forest grew: the root system is damaged, the supply of groundwater to trees changes, and so on. Naturally, these factors affect the growth of the tree and should be recorded in annual rings. Indeed, earthquakes are marked by dark rings, expanded on one side.

Soviet scientist NV Lovelius suggested that the rings of old-timers should contain information about supernova explosions in the Galaxy. He studied the cuts of two such trees: juniper (tree-like juniper) and Amur larch. When the annual layers of juniper found high in the mountains of Central Asia were counted, it became clear that this plant was born in 1163 and lived for 807 years. During this time, three supernova explosions 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 suppression reached a maximum 15-16 years after the explosion, 30 years later the growth of trees returned to normal. What physiological processes are violated under the influence of a supernova explosion has not yet been established.

Reading the annals of the rings, you can extract other information. For example, trees can tell about the degree of atmospheric pollution in different years. American physicists use annual rings to determine the consequences of nuclear tests. Chemists, analyzing the chemical composition of annual rings, study the distribution of trace elements in different periods.

Every time we re-read our favorite book, we find in it something new for ourselves that we had not noticed before. So it is with the chronicle of the 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.

  • Author: Maria Sukhorukih