JOURNAL OF FORESTRY 



Vol. XVI MARCH, 1918 No. 3 



STUDIES OF YIELD AND REPRODUCTIOxN OF WESTERN 

 YELLOW PINE IN ARIZONA AND NEW MEXICO 



By G. A. Pearson 

 Forest Examiner, Fort Valley Experiment Station 



Western yellow pine, because of its abundance, its accessibility, and 

 the superiority of its product as compared with other local species, is 

 and will always continue to be by far the most important timber tree 

 in the National Forests of Arizona and New Mexico. In view of this 

 situation it is but natural that silvical studies should be focused on 

 western yellow pine. Not only its commercial importance, but also 

 its silvicultural needs entitle this species to first consideration. Be- 

 cause of the adverse conditions under which it grows, the perpetuation 

 of the western yellow pine forest in some sections of the Southwest 

 is a matter of vital concern to foresters. This applies particularly to 

 the National Forests on which exploitation has been greatest, namely, 

 the Coconino and the Tusayan. 



Studies of growth and reproduction of western yellow pine were 

 among the first steps taken by the Forest Service in placing the forests 

 of Arizona and New Mexico under management. These studies, be- 

 ing designed to meet the most urgent immediate needs as quickly as 

 possible, were of necessity more or less incomplete and superficial. 

 Studies of growth by the stem-analysis method are unsatisfactory for 

 the irregular and many-aged stands in the Southwest, because they do 

 not take sufficiently into account mortality and the effect of incom- 

 plete stocking, both of which are uncertain factors. Stem analyses 

 indicate the rate of growth for individual trees, but the results arc un- 

 reliable when applied to stands. Studies of natural reproduction were 

 almost entirely by the historical method, that is, data regarding the 

 factors favoring or retarding reproduction were deduced from the 

 history, as far as it could be worked out. of typical areas on whicli 

 reproduction was conspicuously present or absent. The difficulty 



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