Tree Rings and History in the Western 

 United States' 



By Edmund Schulman 



Associate Professor of Dendrochronology 

 University of Arizona 



[With 4 plates] 

 INTRODUCTION * 



The common opinion that the rings so obvious on cross sections of 

 most trees may be counted to give the age of the tree, and that the 

 succession of wide and narrow rings may be interpreted as reflecting 

 the history of favorable and unfavorable growth years, is indeed old — 

 surely the statement by Leonardo da Vinci near A.D. 1500 to this 

 effect is the earliest only because far earlier ones were not recorded 

 or have been lost, perhaps in the disappearance of the Alexandrian 

 Library ! 



Despite this ancient recognition of tree rings as a historical index, 

 modern scientific research on ring growth at first quite properly 

 emphasized botanical and ecological aspects. By the end of the 

 nineteenth century a truly vast amount of work had been done on 

 the nature of such growth layers and their complex relationships 

 to climatic and other factors. 



In recent decades, however, many investigators in this country and 

 abroad have sampled various forest stands and have measured several 

 millions of annual rings in an effort to develop long chronologies 

 which might represent, to some extent, histories of past rainfall, tem- 

 perature, river flow, and other climatic variables. The stimulus for 

 this activity arose, in good part, in an astronomical objective ! Quite 

 independently, it occurred to a Dutch astronomer, later renowned for 

 his contributions on stellar statistics, and to an American astronomer, 



' Reprinted by permission from Economic Botany, vol. 8, No. 3, .Tuly- September 

 1954. 



* Literature citations have been almost completely omitted from this article ; 

 see research reports in the Tree-Ring Bulletin from 1934 on, and an outline bibli- 

 ography in the Compendium of Meteorology, Amer. Meteorol. Soc, 1951, p. 1029. 



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