2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. Ill 



miles from the site of the trees, in the use of a single radius to repre- 

 sent the entire volume growth of a tree, and in the emphasis on a 

 single growth factor. However, if significant results can be obtained, 

 in spite of handicaps, by proper selection of trees from the correct 

 habitat, a critical test is highly worth while in view of the simplicity 

 and directness of method. Heretofore, many of the correlations^ 

 between tree growth and rainfall have been discouraging unless the 

 data were smoothed to an extent that direct responses were masked 

 and only general trends revealed. 



LOCATION AND TREE DESCRIPTION 



The increment cores came from trees that grew near and on Holman 

 Pass, in the Sangre de Cristo Range of north-central New Mexico, 

 about 41 miles by road or about 35.5 miles airline north-northwest 

 from Las Vegas (fig. i). In so far as the life zones were concerned, 

 the collection extended upward from mid-Transition into the lower 

 portion of the Canadian. 



All the trees sampled were dominant or codominant and in the 

 timber stage of development.* On the whole, the ponderosa pines 

 were slightly more mature than the other species. Neighboring trees 

 not sampled were sufficiently distant to avoid undue competitive in- 

 fluence as far as site factors were concerned. Furthermore, the 

 locations were chosen so that abnormal drainage toward or away from 

 the trees was at a minimum. The soils were in no sense tight or 

 lacking in aeration. 



In all, nine trees were sampled and designated by the initials HPC, 

 for Holman Pass Collection. The trees from which samples HPC i 

 to 4 were taken grew on a nearly flat area a mile southeast of the 

 Pass at an elevation of 9,000 feet. All four were within 150 yards 

 of one another. The black soil contained numerous pebbles and 

 boulders. Cores HPC 5 and 6 came from trees that grew on the 

 Pass itself at an elevation of 9,450 feet. In spite of the fact that 

 the site was on top of the actual pass, the trees stood in the middle 

 of a broad, essentially flat area. The soil was derived from shale and 

 sandstone bedrock, fragments of which remained. Between 7 and 8 

 miles west of the Pass and down Rio Pueblo Canyon the location of 



3 Many of these are listed and discussed in Bot. Rev., vol. 7, pp. 687-698, 705- 

 713, 1941. 



•* Following the classification of James W. Tourney and Clarence F. Korstian, 

 Foundations of silviculture upon an ecological basis, p. 268, 1937. New York. 



