Page:Climatic Cycles and Tree-Growth - 1919.djvu/89

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71
CORRELATION WITH RAINFALL.

pond, but of the moving type, as if a belated supply from the snows came to hand and then passed on. The tree was assumed to receive moisture from the current year and from the first and second preceding years; and whichever of the three was greater, that one had the more effect. The application of this formula is shown in figure 20.

Climatic Cycles and Tree-Growth Fig 20.jpg

Fig. 20.—Huntington's early curves of sequoia-growth and rainfall compared with growth calculated by a conservation formula.

But on identifying the rings in the trees collected from that locality in 1915, and especially on finding the soft, delicate parts of the 1915 ring on D-5, it seemed fairly certain that the curve of growth given in figure 20 is one year in error through the omission of a final ring. The growth, then, which appeared to be 1902, for example, and for which a pronounced conservation was necessary, really came the year before,

Climatic Cycles and Tree-Growth Fig 21.jpg

Fig. 21.—Comparison of Fresno rainfall (after Huntington) and sequoias D-1 to 5.

and less conservation or none was needed. The comparison of the same rainfall curve with the old sequoias of the present series is given in figure 21. In this the agreement is not as good as at Prescott, but there is marked similarity in many details. My curve from very old