To understand processes which are best understood over long time scales accurate dating is necessary. Dendrochronology "tree ring dating" often permits events which occurred thousands of years ago to an exact year. Tree rings are also important because of the environmental information then contain. With such data it is possible to examine a wide range of issues, including for example how populations responded and adapted to environmental change.
The Laboratory of Tree-Ring Research (LTRR) at the University of Arizona is the sole source of archaeological tree-ring dates in western North America. With continuing National Science Foundation (NSF) support, LTRR operates an analysis program for tree-ring samples collected by LTRR and other archaeologists from Alaska to Peru and from the Pacific Ocean to the Mississippi River. NSF support allows the program to keep pace with the ever growing demand for archaeological tree-ring dating, information, and assistance and to maintain high production levels and short turnaround times. On average, more than 1,000 dates from 4,000+ archaeological tree-ring samples are produced annually. These data are integrated into relevant archaeological contexts to construct refined cultural sequences and examine important issues of past human behavior that cannot be addressed without accurate, high resolution temporal control. Among these topics are absolute site, locality, and regional chronologies, social organization, intergroup interaction, and cultural adaptation to physical and social environments. In addition, the program promotes the expansion of archaeological tree-ring dating into new regions such as the Southwestern deserts, Great Basin, Great Plains, Rocky Mountains, Alaska, and Mexico.
The project has additional intellectual merits. Exact dating and chronology building are crucial to understanding human behavior, human-environment interactions, and processes of sociocultural stability, variation, change, and evolution. Either directly or indirectly (through tree-ring dated ceramics), tree-ring dating underlies the chronology of Southwestern prehistory and many aspects of the documented history of the region. The project also generates dendroclimatic reconstructions that are combined with reconstructions produced by other paleoenvironmental disciplines such as geology, pollen analysis, volcanology, and trace element studies. In addition to illuminating past environmental processes, these integrated reconstructions provide a solid empirical foundation for examining the interrelationships between human behavior and environmental variability. Finally, the project's efforts to expand research into areas previously thought to be unsuitable for archaeological tree-ring provide absolutely dated "hinge points" for archaeological chronologies in the Sonoran Desert, the Great Basin, the western Great Plains, and northern Mexico.
The project has a wide range of broader impacts. Its findings are almost immediately integrated into undergraduate and graduate classes in anthropology, geosciences, and other disciplines at the University of Arizona and other academic institutions. In addition, the project interacts with K-12 programs, provides instruction for visiting scholars from around the world, and facilitates field and laboratory training for governmental, private, and Native American programs. The LTRR tree-ring sample collections and data archives are unparalleled, easily accessed resources for archaeological research, and an under-construction digital database will enhance the research value of these resources. Increased understanding of long-term human adaptation to cultural and environmental variability and enhanced knowledge of past environmental processes help develop and implement environmental and social policy. Project personnel have contributed directly to formulating policy for managing cultural and natural resources by federal, local, and tribal land management agencies.
