12 CLIMATIC CYCLES AND TREE-GROWTH 



Cedar of Lebanon and archaeological material — This cedar is 

 chiefly found in mummy cases, which from the earlier dynasties show 

 beautiful ring systems, very pronounced but somewhat complacent. 

 The wood is not so good as yellow pine or sequoia, but as approximate 

 dates are known its records are valuable. 



The prehistoric ruins of the Southwest have large numbers of pine 

 and fir logs used as beams. These offer the finest records and a very 

 valuable collection has been made. Even the charred ends of beams 

 that remain in some walls of burnt-out kivas give perfectly good ring 

 records which permit the "relative" dating of the construction period. 

 Juniper, cedar, and pinyon have been used in the same ruins and many 

 sections have been saved, but so far little relative dating has been done 

 on them. Engelmann spruce also occasionally is found, but it has failed 

 to be of value. Several cottonwoods give too short sequences to be 

 worth while. Certain buried pines from the vicinity of Flagstaff give 

 very fine ring records with other interesting features. 



LOCATION OF TREE 



Regions which have been recently cut over will offer the best 

 facilities in getting good specimens from the stumps. A full day or more 

 may well be spent in marking the stumps from which pieces will be cut 

 later by workmen. This selection is very important, for one wants a 

 group that will cross-identify and at the same time will fully represent 

 the forest and the general locality. 



Homogeneous area — One needs, in the first place, to collect from 

 a homogeneous area, that is, an area in which the various trees have 

 somewhat similar conditions, enough to give similarity in rings, for 

 on this recognition of the same rings in each depends assurance of 

 climatic effects in the trees and reliability of dating of rings. To limit 

 one's self to a homogeneous area means that the group will not extend 

 to opposite sides of a large mountain. In northern Arizona differences 

 of a few hundred feet in altitude do not usually affect the rings, but 

 differences of 1,000 or 2,000 feet do sometimes affect them. Westerly 

 or southwesterly exposures are somewhat preferable, as that is the 

 direction from which the storms come and there can be no "shadow" 

 or other local effect. 



Wide sampling — On the other hand, the group should not be con- 

 densed, but should extend a good portion of a mile at the least, so that 

 no alteration can arise from some special condition affecting a part of 

 the group. 



Grouping — The tree bored, or the stump cut, is better if not near 

 other trees. Trees under 10 feet apart are apt to have an effect one upon 

 another by undue shading or appropriation of moisture. This causes 

 eccentric growth of the rings, throwing the major radius away from the 



