10 CLIMATIC CYCLES AND TREE-GROWTH 



Sequoias — In this review of western trees the mountain sequoia 

 (Sequoia gigantea) easily takes a leading part in company with the 

 yellow pine, for besides its great age it has a fundamental feature of 

 greatest importance, namely, cross-identification over large areas. 

 In this character we recognize climatic influences. The ring-growth 

 in the big sequoia is not so sensitive as in the yellow pine, and perhaps 

 any individual tree is a little less certain to identify with its neighbors, 

 but yet cross-identification is very sure in that species and extends 

 through all the mountain sequoia groves from Calaveras on the north 

 to Springville on the south, 200 miles. The southern groves, which 

 yield the best results, give a record obviously similar to that of the 

 yellow pines in neighboring locations. It is true that the sequoia 

 needs a large moisture supply, probably more than it usually gets, 

 but its location is so high on the mountains that the winters com- 

 pletely interrupt the growth and therefore make the record in the 

 rings very reliable as to its annual character. The great age of this 

 tree gives it a second fundamental value. It is astonishing, for ex- 

 ample, to find over considerable areas similar identifiable rings near 

 1,000 b. c Further study upon the sequoia will improve our knowl- 

 edge of the normal growth-curve in relation to age, so that we can by 

 extrapolation tell with some precision what the climate was 3,000 

 years ago. This requires many corrections, such as that for flare of 

 the base, for slanting rings, and lor the indentations of the trunk which 

 come from root relationship. All these factors differ so much in indi- 

 vidual trees that it would seem profitable to study each tree specially, 

 and in recent collecting I have made notes about every stump and have 

 distributed the ages more carefully. (See Huntington, 1914.) 



Coast redwood — The coast redwood (Sequoia semper •virens) has 

 been a disappointment, because after most careful tests it has failed 

 entirely to show cross-identification. This is undoubtedly due to its 

 climatic environment. Various attempts to make use of this tree are 

 described below (Chapter VI). 



Junipers — The junipers and cedars are important in this review, 

 because in Arizona mountains they border the yellow pines on the 

 lower and therefore the warmer and drier side. As one ascends from 

 the desert to the forest areas, the first dark-green rounded trees are 

 the junipers of several different species. The growth of the juniper is 

 slow and the rings are often attractive, but for actual use disappointing. 

 One species branches at the ground and so seems impossible; another 

 has deep vertical indentations in the trunk, with erratic rings. The 

 growth can rarely be traced from lobe to lobe of a cross-section. Often 

 the rings condense so that identity is hopelessly lost.* The more 

 promising species is the pachyphlcea or alligator-bark juniper, which 



* Some successful work has recently been done on the junipers. 



