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project tree age a tree
How can you tell the age of a tree? If it's still growing, the best and most accurate way is to find out its planting history - when it began to grow. You can also get a pretty good idea how old a living tree is by measuring the cicumference of its trunk (how far around it is) and doing a little bit of maths. But when a tree has been cut down, the best way to know its age is to look at a section of the main trunk, and 'count the rings'.
Each year a tree adds a new layer of sapwood all the way around underneath the bark. Most of this happens in spring, giving a lighter colour, and slows down in summer, giving a darker colour. Each pair of rings equals a year's growth, so count the rings and you know the age of the tree. (We can also tell things about the changing climate from a tree's rings: bigger rings can mean more rainfall and better growing weather that year).
So, cut through a tree trunk and you are looking at a cross-section calendar of history - as you can see in the great Mark Twain redwood tree below...
This is the section of trunk from the Mark Twain tree displayed in the American Museum of Natural History, New York with important historical events marked on the growth rings...
This is the moment when, after 1484 years of growing, the mighty Mark Twain tree was felled...
This is the section of tree in
the American Museum of Natural History, New York today...
...and here are the families of the woodcutting community all sitting or standing on the new stump of the tree.
...and here is the stump that still remains - with all its root system still in the ground - in California's Kings Canyon National Park.
...and here is the Mark Twain tree - and its woodcutters - in 1891 just after it had been cut down.
