Tree-ring research is helping scientists build climate and wildfire history in Arizona, including even how severe long-ago fires were.

When lower severity fire damages the outer bark of a tree, it leaves behind a scar that can be seen in the tree's rings. But, when a higher intensity fire wipes out an area of forest, that area is replaced by new trees of about the same age.

From this evidence, dendrochronologists can create a fire history and record when fires happened and at what intensity.

Don Falk, a professor in the University of Arizona's School of Natural Resources and the Environment, works in the UA Laboratory of Tree Ring Research studying how fire and climate affect forests in the Southwest.

"Because of our ability to date each ring to the year, and the fact that in the right environment trees stay around for a long time, we have this extraordinary ability to see ecological events thousands of years ago," Falk says.

From this data, researchers can understand past fire patterns and how development and land use have affected wildfires. It is also possible to create a climate record from the tree ring data and understand how climate changes are contributing to higher severity fires, Falk says.

The oldest dated trees are housed at the tree ring lab, giant sequoias going back 3,000 years.