Page:Climatic Cycles and Tree-Growth - 1919.djvu/61

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47
COLLECTION OF SECTIONS.

could not be identified at all, chiefly owing to large numbers of compressed rings in the last 500 years or more, and to several heavy fire-scars and its generally complacent character. In 1919 a short radial sample was cut from another part of the stump and a complete and satisfactory identification obtained. It shows very fine rhythmic growth in places. No. 13 was not included in the final averages, because its rings were very complacent and perfect identification was not obtained. Nos. 14 and 15 were obtained from the northern side of the valley and their identification was entirely satisfactory. The agreement which they give with Huntington's "first year of tree" has already been quoted.

The three groups whose collection has been described above showed on examination certain interesting relationships to the location in which they were found. The first group was obtained high up on a hillside, where the slope of the ground was 15° to 25°. It was not very far from the top of a sharp ridge and there was no opportunity for moisture to collect and remain for long periods on the soil. Therefore one would expect these trees to show variation related to the amount of snowfall each winter, if any did. The growth of some of these trees was large but full of constant variation, and they were therefore of the type which I have called "sensitive." They do in fact show best of any the relationship to precipitation which will be described in a later chapter. The second group came from a characteristic feature of the country, namely, a basin with thoroughly water-soaked soil.

The luxuriance of vegetation in these basins before lumbering was wonderful. The sequoias grew often within a few feet of each other, and even between them were pines, firs, and cedars. Lumbermen often point out the bottom of a basin and say that such a place ran over 1,000,000 board feet to the acre. To-day nearly all the trees are gone and debris and rubbish are scattered about everywhere. The constant supply of water in the basin made the trees less dependent upon the annual precipitation and they show, in fact, large rings with very slight variation from year to year. They are typical examples of the "complacent" habit. Complacent trees contribute much less to a knowledge of climatic variations, and some of them have to be discarded because of uncertainty in the dating of their rings.

The third group, Nos. 12 to 15, came from Indian Basin, where logging had been done about 1903. Its outlet, like the others, was toward the northeast. It had, however, a much larger flat area, now covered by extensive fields of hay and by forage. The characteristics of the trees found here were the same as in the groups already described.

No. 1 (with a 7-foot radius) was first counted and marked with provisional dates. The rings were coarse and the numbering seemed promising, but proved later to have 6 to 8 errors in the last 700 years. No, 5, which was the tree cut down during my visit, was then dated