UA tree ring researchers find evidence of oldest tree in Arizona

By Edina A.T. Strum
Arizona Daily Wildcat
November 21, 1996

A thousand years of history is about to be uncovered as the oldest tree south of the Mogollon Rim is analyzed by the UA's Tree Ring Research Laboratory.

Last year, during a trip to the Pinaleno Mountains, about 75 miles southeast of Tucson, Ed Wright, graduate research assistant at the tree ring lab, found and took samples from a tree he believed was very old.

"We look for certain characteristics - spiral grains, weathering and lichen or moss growth - that let us know the tree may be very old," he said.

The tree Wright found last year was dated back to A.D. 1101. That tree was a "snag," or dead-but-still-standing tree. This year, Wright went back to the same area to look for even older trees and found two more "snags."

The oldest living tree in the area is a Douglas Fir that dates to A.D. 1257 and was discovered by Henri Grissino-Mayer, research associate at the tree ring lab. However, the 1257 tree was so badly burned in the Clark Peak fire earlier this year that "it probably is not going to survive. I predict it'll be dead within three years," Grissino-Mayer said.

The newest samples date to A.D. 950 and 876 and are so old the lab couldn't use existing chronologies of the area to date the wood - no other samples are old enough, Wright said.

"These newest samples were compared to trees in the Sandia Mountains (in New Mexico)," he said.

Grissino-Mayers said two important research projects will come out of the latest discoveries - better climate reconstruction and archaeological dating of sites in the area.

"These 800 and 900 A.D. trees will tell us how much rainfall fell in those years," Grissino-Mayers said. "Tree-ring dating is widely used for climate reconstruction because the past is the key to the future."

The archaeological applications are equally exciting, Grissino-Mayer said because "we will be able to date sites that have never been dated before in Southern Arizona."

Jeff Dean, dendochronology professor, specializes in the archeological applications of the dating process.

He said archaeologists are already studying sites in the Pinalenos and when they have wood samples, such as roofing beams, they will send the samples to the tree ring lab for analysis.

Dean will look for the tree ring growth patterns in the archaeological samples and compare them to forest samples that have been dated in the area.

The point where the patterns overlap gives the archaeological site date - these thousand-year-old trees have "pushed back the chronology" a couple of hundred years, Dean said.