300 CARNEGIE INSTITUTION OF WASHINGTON. 



From 1001 A.D. to 1900 A.D. it is based upon all of Huntington's material. 

 Only the age stage from 1301 to 2100 years was used and only correction for 

 flaring was applied. The part from 1001 B.C. to 1000 A.D. was composed 

 of all of Huntington's material belonging to the groups 20 to 31. It was 

 corrected by groups in the usual way. 



The variations of the final curves, corrected for variations depending on 

 flaring and on different rates of growth according to age, may largely be 

 due to changes in climate and weather, for influences caused by shading, 

 liberation, abundant seed production, defoliation or other injury caused by 

 insects, fire, frost, wind, etc., are essentially eliminated by the great number 

 of measurements from different regions and by omission of trees showing 

 such effects. A comparison of these curves and Huntington's curve, ob- 

 tained in a different way, reveals the remarkable fact that they all agree in 

 those parts that are computed from a very large amount of material. Thus, 

 the correspondence is particularly good, partly even detailed, since 800 

 A.D. All the curves show maxima in the beginning of the tenth and eleventh 

 centuries, during the fourteenth century, and since about 1550. They 

 have minima in the latter parts of the tenth and twelfth centuries and about 

 1300 and 1500. The agreement evidently is real and almost surely of climatic 

 origin. Thus, the growth of the big trees, allowance being made for effects 

 of casualties, etc., is essentially determined by a combination of factors, and 

 the role played by each factor is subordinate and varying. 



The chief climatic factors influencing the growth appear to be precipitation, 

 temperature, and sun radiation. The relative role of each factor is dependent 

 on the time for its effect, upon other factors, upon internal conditions in the 

 tree, etc. Thus, growth can primarily follow now this, now that factor. 

 No direct study of the relationship was ever made, so that not even the 

 general laws are known. 



In the case of the big tree the importance of the individual factors is much 

 more difficult to estimate as data of temperature are entirely wanting. 

 However, it appears to be certain that the sequoia curves do not specially 

 record precipitation; high parts in the curves might directly or indirectly be 

 connected with periods of heavy rainfall and low parts with scanty rainfall, 

 but it can not be concluded that all high and low parts were so. In this 

 connection it is worth mentioning that the tree-growth maximum during 

 the fourteenth century coincided with an exceptional spottedness of the 

 sun and with the climatic stress of which there are abundant historical 

 records in the Old World, and which particularly expressed itself in un- 

 usually cold winters, cold rainy summers, and devastating storms. Ac- 

 cordingly, before satisfactory interpretation of the sequoia curves and 

 conclusions from them regarding the climate of the past and regarding the 

 relationship between variations of growth and fluctuations of lakes and 

 changes of human culture in the Southwest can be made, it is necessary to have 

 data on temperature, better knowledge of the relation between precipitation 

 and growth of sequoia trees in dry situations, and general knowledge of the 

 role of the sun radiation for growth. 



Besides being of climatological interest the sequoia curve is of importance as 

 eventually affording a possibility to extend the Swedish post-glacial geo- 

 chronology up to present time. This chronology, worked out — not yet pub- 



