16 CLIMATIC CYCLES AND TREE-GROWTH 



Long-record trees — (1) Pines. If very large living pines are in 

 moist valley-bottoms, they are not likely to be of maximum age, 

 that is, over five centuries; but if they are near 60 inches in diameter 

 and growing on a ridge or hillside, especially above a dry valley, they 

 are likely to contain a valuable record. Of course, in such cases one 

 checks the estimate by a core from the increment borer. (2) Sequoias. 

 The oldest sequoias are not close to running water nor yet on exposed 

 ridges, where stress of storms does not permit great age, but they are 

 somewhat between these situations and usually near, though not at, the 

 higher levels of the grove. This description applies well to the 3,200- 

 year tree at Converse Hoist and the 3,100- and 3,000-year trees at 

 Enterprise. A 2,800-year tree at Converse Hoist was nearer the top 

 of a low ridge than one would have expected. A number of 2,200-year 

 trees were well outside and yet not far from the thickly covered swampy 

 basins, and they extended up the valleys to the highest levels of the 

 groves. In the lower levels the trees were apt to have a large supply 

 of ground water and some very large trees had only 1,500 to 2,000 

 years of age, such as the "Big stump" at Wigger's (General Grant 

 Park) and the Dance Hall stump at Calaveras Grove. 



Collection for age compensation — Samples for this purpose must 

 obviously be taken from the immediate vicinity of the old trees whose 

 records are to be checked, and in the same topography. 



Climatic comparison — In collection for climatic comparison, one 

 uses the general principles of selection already enumerated, remember- 

 ing that one gets little if anything from young trees. Mature trees 

 are much preferred, and even the largest and oldest, for in such cases 

 the 9 or 10 inches of core cover a great number of years. On the 

 other hand, very slow growing trees from the tops of dry ridges may 

 be impossible to date without some neighboring younger trees, and 

 it is safe nearly always to include a very few younger trees to assist in 

 this operation. Trees very near a road are apt to be erratic from injury. 



Age estimates in sequoias — Age estimates are a necessary part 

 of collecting, especially in sequoias. The best criterion is the size of 

 the outer rings, coupled with the total diameter of the tree. A promis- 

 ing tree should be over 20 feet in diameter above the bulging base, 

 or near 25 feet at the very maximum. The rings at various places in 

 the outer parts should get down to a few tenths of a millimeter or 

 about a hundredth of an inch. On most of the very old trees there is 

 a burnt space in which a few chips or bits of charcoal will give a sample 

 of the rings. An increment borer is still better and may be used through 

 a thin place on the bark of a living unburnt tree. The largest tree, 

 showing over 30 feet in maximum or bulge diameter, if near running 

 water, is not likely to add much to our climatic record. But if such a 

 tree is on a dry hillside its age is worth investigating, and if it still 

 promises well, some apparatus for boring it to the center could be devised. 



