University of Arizona, Laboratory of Tree-Ring Research
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- The Laboratory of Tree-Ring Research (LTRR) curates an estimated 2,000,000 scientific specimens and their associated records. A significant portion (i.e., hundreds-of-thousands) of the materials curated are done so on behalf of and in collaboration with the U.S. Department of the Interior, specifically its National Park Service, Bureau of Land Management, Bureau of Indian Affairs, and U.S. Fish and Wildlife Service. The collection includes extensive holdings from both natural history and archeological contexts. Established in 1937, the LTRR is an interdisciplinary department at the University of Arizona. The LTRR's long-standing international renown derives from extensive contributions to research, teaching, and public service in dendrochronology, a field founded in the early 20th century by LTRR's first director, A.E. Douglass. “Dendrochronologists” study tree rings as natural chronometers and as recorders of change in the environment with which all biological life and human cultures are inescapably linked. Tree rings are especially valuable for yielding absolute, single-year dates for past events and processes and provide a pre-industrial perspective on cultures and environment that is otherwise unattainable.