100 



CLIMATIC CYCLES AND TREE-GROWTH 



Sequoia growth and rainfall — The attempts in the previous volume 

 to find a real correlation between sequoia growth and precipitation 

 (p. 70) were not satisfactory. Figure 10 shows a decided improvement 

 brought about by the high-level trees, D 1-5, corrected for gross rings 

 and compared with rainfall at San Francisco. There seems to be a real 



1850 I860 1870 1880 1890 1900 1910 



Fio. 9 — Cibecue drought record traced directly from autoplot 



1920 



relationship here, even though it does not yet equal the Prescott 

 correlation. 



Comparison records — There is yet much to be done in this com- 

 parison between tree-growth and rainfall, but the obstacle everywhere 

 is the lack of rainfall records near the trees and over adequate periods 

 of time. The five Prescott groups showed that in a mountainous 

 country nearness is very important. Until very recently the nearest 

 records to the sequoias were 65 miles away and at an elevation 500 



San Francisco rainfall 



Mlj 

 3.0 jf 



zx>.S 



i-o, 



1850 I860 1870 I860 1890 1900 



Fio. 10 — Sequoia growth and rainfall 



feet lower. Colonel John R. White, superintendent of the Sequoia 



National Park, is greatly to be commended for starting adequate 



records there. 



CONSERVATION 



In the Prescott correlation, as discussed in Volume I, a conser- 

 vation formula was applied, based on the idea that the accumula- 

 tion of excesses or deficiencies in moisture affect the general activity 

 of the tree. One might say that the trees respond each year to 

 the amount of rainfall, but that their vitality is affected by the 



