How do trees develop annual rings?

Question

...you know, the ones that help determine the age of the tree.

Answer 1

well its actually the laying down of new xylem and phloem in the outer part of the wood.

This is dragging up old distant memories, but there is the cambium strip that separates the internal and now pratcially "dead" wood inside it and the current and "live" outer xylem and phloem (although xylem is technically dead cells anyway..you get my point).....now this xylem and phloem carry the water from roots (xylem) and sugars etc from leaves to various parts of the plant (phloem).....its being constantly laid down, but during the spring and summer its laid down faster and cells are bigger and more of them, during the winter its much less or not at all....this is what we see as tree rings....where the winter cells are dense and small and seen as more of a ring, while the summer wood is much bigger and its less densely put and is the "bits" in between.

You can see that different summers etc were colder or more harsh (ie drought) if there is less wood laid down and if its great growing conditions the "ring" will be wider so its important for looking at weather patterns in the past too!!!

Answer 2

The short answer is that during the growing season, the tree grows--a lot, and the wood created during this time is visibly less dense than during the parts of the year when it is growing slowly or not at all. Since the seasons happen every year, the result is rings that tell the tree's age.

Answer 3

Tree usually create rings inside the tree that we cannot see. Take extreme winter in Pine Tree, for example, pine tree don't create new wood because its too cold for the pine tree to grow bigger, thus gets weaker. If there's no harsh winter and all sunny, then it grows stronger, and forms lighter color of ring. Dark means extremes weather, light means non-extreme weather.

When the tree dies and you cut the trunk, you can see rings and it will tell you how old this tree have lived and what kind of condition did this tree survived. If its all dark, it means this tree have lived through series of extremes. If its all light, it means this tree have survived in a non-extreme weather. If there's a mix, this means tree have lived through extremes and non-extremes weather.