How do you judge the age of a tree from its rings?

Wood has a long life. There are often many trees in nature that are over a hundred years old, even thousands of years old. At first glance, it seems difficult to know their age. However, when people understand the growth characteristics of trees, they can roughly tell the age of a tree. "Tree rings" is a good method.

Tree rings, as the name implies, are circles formed by trunks every year. Inside the phloem of the tree stem, there is a circle of cells that grow very actively and divide very quickly, and can form new wood and phloem tissue, which is called cambium. It can be said that the sturdiness of the trunk depends on its strength. These cells grow obviously differently in different growing seasons. The weather from spring to summer is most suitable for the growth of trees. Therefore, cambium cells divide quickly, grow fast, are large, have thin cell walls, have few fibers, and have many conduits for transporting water, so they are called Chunmu or Zaomu. In autumn, due to the gradual weakening of cambium cell activity, the cells produced are of course not very large, with thicker cell walls, more fibers and fewer vessels, which are called autumn wood or late wood.

Choose a piece of wood sawed from the trunk of a big tree and observe it. You can find that the trunk is made up of circles, and the texture and color of each circle are different. Through the above analysis, we can draw a conclusion that the early wood was loose in texture and light in color; It is late wood with dense texture and dark color. Early wood and late wood are combined into an annual ring, which is the wood formed by trees within one year, called annual rings. There is only one ring in principle, so it is easy for us to know the age of a tree according to the number of rings. But there are also some plants, such as citrus, whose annual rings do not conform to this law. We call them "fake annual rings" because they can grow rhythmically three times a year to form three rounds. So it's not three years.

Tree rings can be said to be a reliable record of the age of trees.

But then again, tree rings are not the only magic weapon to know the age of trees, because not all tree ages can be measured by tree rings of several years, and only trees in temperate regions are more prominent. Trees in tropical areas, because the seasonal change of climate is not obvious, there is no difference in the cells produced by cambium, and the annual rings are often not obvious. Therefore, it is of course more difficult to calculate its age.