Page:Climatic Cycles and Tree-Growth - 1919.djvu/52

From Wikisource
Jump to navigation Jump to search
This page has been validated.
40
CLIMATIC CYCLES AND TREE-GROWTH.

OLD EUROPEAN TREES.

It is of course most desirable to carry the tree-records back as far as possible for verification of any feature observed in recent years and for additional information. But one is met by the rapidly diminishing number of specimens and the liability of obtaining records which are not representative of the regions on account of the increasing effect of individual and accidental variations. It is true that in the very homogeneous region about Flagstaff, Arizona, an average of 5 trees and even of 2 gave a valuable record corroborated by comparisons with larger numbers; but in these European groups the oldest trees are all from the Scandinavian peninsula, and probably the individual trees of which I have samples are representative of widely different localities in a rugged and mountainous country. Even though not homogeneous, the 15 oldest trees have been segregated in 2 groups covering the interval from 1740 to 1835.

Group A represents the inner coast of Norway and includes the following trees: No. B 3, Ös, south of Bergen; No. B 11, Sopteland, south of Bergen; No. B 12, Sogne Fjord; No. B 15, Hardanger Fjord; No. B 16, Sogne Fjord; No. N 2, latitude 68° 45'.

Climatic Cycles and Tree-Growth Fig 10.jpg

Fig. 10.—Growth of old European trees. A, six Norwegian trees, mostly from inner fjords. B, eight trees from Dalarne, Sweden.

Group B is made up of 8 trees from Dalarne, central Sweden, and 1 from Lapland, latitude 64° 30'. This group, therefore, represents somewhat more homogeneous conditions, but yet it can not be well summarized in its larger fluctuations. When plotted with Group A, as in figure 10, it shows the latter to have a considerable tendency to reversal, a characteristic already observed in this region. But there are discrepancies in Group B consisting of sudden depressions in growth