Page:Climatic Cycles and Tree-Growth - 1919.djvu/35

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27
COLLECTION OF SECTIONS.

THE SECOND FLAGSTAFF GROUP OF SEVEN SECTIONS.

In 1911 the writer visited Flagstaff again and made a trip into the forest where cutting was going on, in order to procure a few additional samples of the yellow pine which would check the recent part of the tree-record previously obtained and bring it up to date for comparison with rainfall values. The location was about 12 miles southeast of town and from 6 to 12 miles east of the region from which the first Flagstaff group was obtained. Seven cuttings were procured from the edges of stumps, thus bringing away a triangular pyramid of wood, which included the outer 50 to 100 rings.


Fig. 5.—Growth of individual trees compared with precipitation at Flagstaff.

Figure 4 shows how well the second group checks the first and indicates that even a small group of trees, no more than 7 in number, is sufficient to give results of considerable accuracy. Indeed, we may go further and say that a single tree under favorable conditions may give results of very great value. This is evident in figure 5, where the 7 sections from the last Flagstaff group are plotted separately, the most rapid grower at the top, just below the rainfall curve, and the slowest-growing tree at the bottom. All rise alike because the conditions of rainfall in 1900–10 were more favorable than in the preceding decade, but all (especially the curve of section 4) show a more or less close relation to the rainfall at Flagstaff, even though that town was some 12 miles away. The great sinuosity which a quick-growing tree may show is well illustrated in section 4 in the great differences between successive years. A lack of sinuosity is shown in section 5 at the bottom. This difference supports the conclusion already reached that slow-growing trees are of less value than rapid ones in the determination of climatic cycles. The results of the measures of this group serve as a check on the preceding measures and are shown in the figures just referred to. They are, therefore, not tabulated in this book.


THE PRESCOTT GROUP.

Prescott is located in the northerly part of the Bradshaw Mountains, at an elevation of 5,200 feet. The rocky subsoil is largely granite disintegrated at the surface and worn into steep hillsides, deep gorges, and picturesque masses of rounded boulders. The ridges are sharp and rugged, and the general contour is very irregular. There are very