TREE SELECTION 9 



reaches a great age, but its rings are more complacent than those of 

 the yellow pine. It reminds one of a cedar. 



Sugar pine — Sugar pines are fine, large trees, but the rings are 

 large and the age is often disappointing. The distribution is much 

 more limited than the yellow pine; from which one assumes that it 

 will not stand so great a variation of moisture. Ring records of this 

 species on Mount Wilson resemble very closely similar records from 

 the adjacent yellow pines. Like the Douglas fir, it is a good occasional 

 substitute for the yellow pine, but is far from its equal as a standard 

 tree in southwestern climatic study. Substitute trees have given so 

 many cases of satisfactory records that one feels it always worth while 

 to use some other tree than the yellow pine where such standard trees 

 are scarce. 



Douglas fir (spruce) — In the Arizona Mountains this tree borders 

 the pine belt on the upper, which is the colder and more rainy side. 

 It mixes with the yellow pine to a small degree and is the first choice 

 as substitute when the pines are infrequent in any site. The trees, 

 even if bigger, are apt to be younger, with larger growth each year. 

 The rings are usually well marked and free from errors and cross- 

 identify perfectly with neighboring yellow pines. It is somewhat apt 

 to exaggerate climatic influences. 



Other spruces — The Sitka spruce of our northwest coast (tested 

 in Oregon and Washington) has heavy, emphatic rings of a complacent 

 sort and so far has not seemed a desirable tree. It grows to exceedingly 

 large size. A fine specimen some 9 feet through, in the American 

 Museum in New York, gives a good idea of what it is. This particular 

 specimen exhibits some very unusual spiral gross-rings whose origin 

 it would be interesting to determine. This spruce grows at low, well- 

 watered levels near the coast, and so its value as a climatic record is 

 probably low. 



The Engelmann spruce of high altitudes is even less valuable in 

 this respect. It grows at elevations over 8,000 feet at Pike's Peak 

 and at 10,000 on the San Francisco Peaks (Arizona). Its rings have 

 very little variation and do not cross-identify with neighboring pines 

 and Douglas firs. Owing to these characteristics it has practically 

 no value as a climatic record. 



The European spruce, Picea excelsa, is much better. While more 

 complacent than the very satisfactory Scotch pine there, it does show 

 good ring variations which can be dated and in one or two special 

 cases give a remarkable record of solar variations. Such is No. S 14 

 from southern Sweden, whose photograph is given here (see Plate 9) 

 because it did not come in time for insertion in the first volume. Its 

 curve of growth was given in Volume I, page 75, figure 22. It is 

 therefore unusual and interesting. 



