4.3
Modern extreme weather in the Low Arctic is recorded in growth-rings of shrubs.
Did you know?
Some long lived species not only survive extreme weather but contain records dating back before measurements were possible.
See secrets of dead plants
See secrets of dead plants
Woody species in particular tell us about weather, volcanos and many other events of the past (see new information on "secrets of dead plants" coming soon).
In the boreal forest, tree death from extreme events refreshes biodiversity naturally every few hundred years.
Extreme weather can increase populations of insects that kill or weaken trees and shrubs. Dead and weakened trees and shrubs are better fuel for forest fires.
Trees and shrubs growing in areas where there is a clear difference in climate between summer and winter produce rings in their wood. One ring generally speaking indicates a year of growth because the cells that grow in spring are larger than those that grow in summer. These cells are essentially water pipes, bringing water from the soil to the branches and their leaves, allowing the tree or shrub to grow. In tropical areas, trees and shrubs have much less distinct rings or sometimes no obvious rings at all! How would you find out how old a tree is? See the photo below.
Link for information
Link for information
Shrubs have much narrower rings than trees. Also, often the branches grow close to the ground before turning up and this results in wider rings on the bottom part of the branch than on the top. Specialists, called "dendrochronologists" need to take many things into account to discover the role of climate and extreme weather events.
Get Active!
Modelling Clay Tree Rings
The rings inside a tree can tell us a lot about what environmental conditions a tree has lived through. By looking at tree rings, we can learn about how long the tree has lived, what kinds of climate conditions it has lived through and how much it has grown throughout the different seasons. We can also find out many other secrets (see resource coming soon). Trees can live for hundreds, and in some cases, even thousands of years.
We can count the number of rings a tree has to find out how old it is. There are two different types of rings caused by differences of sizes of the cells and the thickness of their walls. A light-coloured ring is formed by large cells with thin walls and shows how much a tree has grown during the spring and early summer. The light rings are usually much thicker than the dark rings. The dark rings are made by smaller cells with thick walls and show how much the tree grew at the end of summer and in autumn when tree growth becomes slower. Each annual ring consists of a light- and a dark-ring.
Try making your own tree rings so you can understand how to read the patterns in wood.
We can count the number of rings a tree has to find out how old it is. There are two different types of rings caused by differences of sizes of the cells and the thickness of their walls. A light-coloured ring is formed by large cells with thin walls and shows how much a tree has grown during the spring and early summer. The light rings are usually much thicker than the dark rings. The dark rings are made by smaller cells with thick walls and show how much the tree grew at the end of summer and in autumn when tree growth becomes slower. Each annual ring consists of a light- and a dark-ring.
Try making your own tree rings so you can understand how to read the patterns in wood.
You will need:
Instructions
Make a long, thin snake out of one colour of modelling clay.
With another colour, make a snake the same length as the first one, then roll it out length-ways so that it is flat enough to wrap around the first snake.
Repeat this with multiple colours and different thicknesses so you get a varied tree ring. Each layer represents one year (a light and a dark ring together). Follow the photos below for help.
Once you have a complete 'tree' with multiple rings wrapped around, use a knife to cut the 'tree' into one slice. Try not to squash the modelling clay whilst cutting as this will change the shape of the tree rings.
Try to cut length-ways and on an angle too! How do the tree ring patterns change?
Once you have a couple of slices of tree cut, see how many tree rings you can count! How old does that mean the tree is?
Use your tree rings to compare to the wooden furniture in your home and school. Does any of the furniture in your home or at school have the same kind of pattern from one of the ways you cut your 'tree'?
When you cut the tree rings, they should appear like this.
What are the differences in the cuts between these three photos? What do your tree rings look like compared to these below?
On the right, the tree has been cut across, in the middle it has been cut down vertically, and at the left it has been cut down at an angle (particularly the three left-hand planks). On the left, the dark spots are where branches came out of the tree – they are called "knots".