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an Interview with Henri D. Grissino-Mayer
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At the recently concluded 2001 meeting of the Violin Society of America, Professor Henri D. Grissino-Mayer presented the results of his dendrochronological analysis of the Messiah Strad. For those who could not attend he has kindly given us this summation of his science and his findings. Professor Grissino-Mayer introduces himself: I'm
an Assistant Professor in the Department of Geography at the University
of Tennessee. My research interests lie in two general areas, both of
which
include the use of dendrochronological (tree-ring dating) methods. I am
interested in the reconstruction of past climate from tree-ring data,
especially in the Southwestern and Southeastern United States. I've led
the development of numerous millennial-length tree-ring chronologies
throughout Arizona, New Mexico, and Colorado that were used to analyze trends in both
short-term (decadal) and long-term (century-scale) climate during the past
2000 years. Secondly, I use tree-ring based fire history information from the fire-scar record to evaluate the record of past fires in an area. I
spent seven years working under Dr. Thomas W. Swetnam and his colleagues
at the Laboratory of Tree-Ring Research (The University of Arizona) analyzing
fire history in numerous locations throughout the Southwest. During this time, I developed FHX2, software that allowed the processing of large
volumes of tree-ring based fire history data. Q: Describe in general terms the process of dating antiquities by dendrochronological means... A: Any artifact made from a type of wood that originated from the temperate latitudes has the possibility of being dated provided: (1)
it has enough tree rings, If these criteria are met, we should be able to obtain enough measurements of the tree-ring widths to be able to date the tree rings on objects manufactured of wood, even those whose date of manufacture is unknown. Why is this? Because tree growth is variable from year to year, i.e. climate is different in subsequent years. This variability in climate (and therefore in tree growth) causes rings to have "patterns" of wide and narrow rings that are unique over time, much like a "fingerprint". If we can obtain a reference chronology from very long-lived, still living trees, then we stand a chance at dating wooden objects by matching the overlapping patterns of wide and narrow rings. It's simply a matter of sliding the graph of the rings from the unknown object against the graph of the rings of a reference chronology. We can even extend our living tree reference chronology using wood from houses, pueblos, cathedrals, and many other types of structures where old wood can be found. I should point out that dendrochronology is a very visual science. In other words, we can do all we want with the statistics of tree rings, but the truth is in the graphical dating of these patterns. Nothing should be considered dated by dendrochronology unless both the statistics and the graphics indicate without a doubt that the tree rings of the object do indeed date against the reference chronology. cont'd.>
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