Sources of Variation in the Southwestern Tree-Ring Record

Recent analyses of regional tree-ring data sets highlight the importance of assessing the representativeness of the tree-ring record. A number of these studies have used temporal variation in numbers of tree-ring dates, and sites with tree-ring dates, as a proxy record of population change. Sources of variation in tree-ring date distributions are explored through an analysis of three cases, Black Mesa, Mesa Verde, and Cedar Mesa. The analysis employs three variables: number of dates, percentage of cutting dates, and number of construction events involving pit structures. Significant sources of variation in the three data sets include the kinds of structures (surface vs. pit structures) that yield datable tree-ring samples and the settings (open vs. sheltered) of the sites under investigation. Patterning in tree-ring data across regions includes the successful dating of ninth century pit structures, the poor dating of tenth and early eleventh century sites, and the successful dating of thirteenth century cliff dwellings. The analysis suggests that caution should be exercised in employing tree-ring data to study population history.