Climatic Cycles and Tree-Growth

Abstract

PUBLICATION No. 289 of the Carnegie Institution of Washington is devoted to Prof. Douglass's study of the annual rings of trees in relation to climate and solar activity. When the late Prof. Lowell was seeking an ideal climate for his observatory, with the view of studying the planet Mars, he chose the dry region of Flagstaff, Arizona, on account of its low rainfall and high proportion of clear skies. While Prof. Douglass was at the Lowell Observatory it occurred to him that variations in solar activity might have a measurable effect on tree-growth, since the latter was probably dependent on rainfall, and rainfall might very likely be affected by solar activity. He began by studying the yellow pines of those arid regions, arguing that a very dry climate should be the best for such an investigation. He soon found that the intimacy of the connection between the width of the annual tree-rings and the rainfall, when the latter was known, was far closer than he had dared to hope, and he pushed further afield, examining tree specimens and fossils in European collections. as well as in other districts of America.