Tree Ring Research Study Performed by the University of Arizona Laboratory of Tree Ring Research in conjunction with SRP

Why Study Tree Rings? Scientists can study tree rings to learn two things: Age of the tree Amount of growth in that year

But why do we care how much a tree grew in a year? We can find out many things by studying how much a tree grew in a particular year… but you try to figure it out! What does a tree need to grow? Water, Sunlight What do you think makes a tree grow more in one year over another year? More water!! How would a tree get more water one year than in another year? More rain and snow that year!!

We Study Trees to Learn About Water! We can study the size of the tree rings to learn about how much water there was in that year! Then we can analyze patterns of rainfall (precipitation) over time!

Here’s How it’s Done: A tree ring is a layer of wood cells produced by a tree in one year, consisting of two layers: earlywood formed early in the growing season and is lighter in color latewood produced later in the growing season and is darker in color. Earlywood + latewood = one annual tree ring X

Check it out again… X Notice that some layers are thicker, and some are thinner? Why? The thicker layers were years when the tree got more water which means there was more rain/snow that year!

The University of Arizona Study Scientists at the University of Arizona Laboratory for Tree Ring Research analyzed tree rings in trees from the Salt and Verde watershed areas. They were able to study tree cores that dated back to 1330!! They did this to give SRP information about the two watersheds that we use in Phoenix. The data the scientists gathered helps SRP plan for the future!

What did they learn? Scientists found that 1996 and 2002 were the driest years we have ever seen (since 1330) in the area. In fact, 2002 was SO dry, that some trees didn’t even have a ring for that year! This means the trees didn’t grow at all that year because it was so dry!

But…there was good news too! They also found that even in periods of drought, there were years that the Salt and Verde basins got larger volumes of rain and snow. So that means that as long as we capture and store water during wet years, we should have enough to last us during dry years.

Think about it… Even if we may have enough water since we save it in reservoirs, can we waste it? Remember, the driest years in the last 700 years were 1996 and 2001 (VERY RECENT!) What would happen if that trend continues and we see more dry years? WE MUST CONSERVE!!