Brief History of the LTRR

HISTORY OF THE LTRR

In 1901, a 34-year-old astronomer stationed at the Lowell Observatory in Flagstaff, Arizona, began investigating the relationship between tree growth, rainfall, and solar cycles. In 1904, this astronomer, Dr. Andrew Ellicott Douglass, collected his first specimens for tree-ring research while visiting the lumber yards of Flagstaff. He carefully measured the the widths of the individual rings using a steel ruler and magnifying lens. Over the next three years, Douglass would demonstrate the close association between radial tree growth and rainfall, culminating in his first publication in tree-ring research in the journal Monthly Weather Review in 1909. Three years earlier, Douglass permanently relocated to the University of Arizona in Tucson where he continued his studies in astronomy and dendrochronology.

In 1914, Clark Wissler approached Douglass about applying his tree-ring dating methods to archaeological wood from Puebloan ruins in Arizona and New Mexico. Thus began a 15 year search by Douglass and his colleagues for archaeological tree-ring samples that would overlap with the tree-ring chronology developed from living trees. If such an overlap could be found, the construction dates for many Puebloan ruins could be determined to their exact year. Finally, on June 22, 1929, a very unstable beam was extracted from the Whipple Ruin in Show Low, Arizona, and given the identification number HH-39 (after Lyndon Hargrave and Emil Haury). This one sample conclusively bridged the gap between the living tree chronology and the archaeological tree-ring chronology. That evening, Douglass called out the construction dates of ruin after ruin, considered by many to be one of the most exciting moments in scientific discovery.

Early in his studies, Douglass realized the need for separate facilities for conducting tree-ring research. For over 30 years (between 1906 and 1936), Douglass had worked out of his small office at the Steward Observatory (which he helped found) on the Arizona campus. With the acquisition of hundreds of archaeological tree-ring samples, space became cramped, and Douglass seriously considered moving the tree-ring laboratory to another state. In a letter to the university president in February, 1937, Douglass expressed his belief that the university would lose its status as a top tree-ring research facility without greater encouragement from the university. As a result of the letter, the university gave Douglass several rooms and adjoining storage space on the second floor of the recently-built football stadium. In December 1937, the Arizona Board of Regents voted to establish a permanent tree-ring facility, and the Laboratory of Tree-Ring Research was born.

Today, the Laboratory is a division of the College of Arts and Sciences, and conducts a unique program of teaching and research in all aspects of dendrochronology. Graduate-level instruction is offered through cooperating academic departments, and a limited number of graduate research assistantships are available to qualified students. Current research efforts are directed toward:

the quantification of tree-ring parameters
the establishment of new tree-ring chronologies throughout the world
the use of tree rings in the study of forest ecosystems
the reconstruction of paleohydrologic and paleoclimatic variables, and
the documentation and development of prehistoric chronological controls.

Along with the world's largest collections of tree-ring specimens from living trees and ancient timbers, the Laboratory maintains a variety of specialized equipment and data files containing processed tree-ring chronologies, relevant climatic and hydrologic records, and archaeological tree-ring dates and site information. Sponsored research is currently funded by several agencies, including the National Science Foundation, the U.S. Department of Energy, the Environmental Protection Agency, the USDA Forest Service, and the USDI National Park Service.

For more information about the career of A.E. Douglass and the Laboratory of Tree-Ring Research, consult the book Tree Rings and Telescopes: The Scientific Career of A.E. Douglass, written by George E. Webb and published by The University of Arizona Press in 1983. Additional information about A.E. Douglass can be found at the Flandrau Planetarium at the University of Arizona.