Page:Climatic Cycles and Tree-Growth - 1919.djvu/51

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39
COLLECTION OF SECTIONS.

Geological Museum at Berlin, in which the same cycle was prominent. It was not measured, as the date of cutting was not known.

PILSEN (AUSTRIA) GROUP.

This group of 7 Pinus silvestris sections was measured in the office of Dr. A. Cieslar, in the Hochschule der Bodenkultur at Vienna. I have no samples of them in my collection, but they were carefully cross-identified before measuring. Two sections had the ring for 1849 very doubtful, but its identity was verified by comparison with the others. The average date of the center was 1821 and the average size 11 inches in diameter. They all came from a forest station near Pilsen, in northwestern Austria. I have not seen the locality, but judging by the appearance of the country a little farther south the mountains are not rugged.

The mean measures upon this group from 1830 to 1912 are given on page 114; their plot is in figure 8. The curve is very peculiar, and it is hard to say how it should be corrected for age. It descends sharply from 3.62 mm. in 1830 to 1.25 mm. in 1851, and from that point on it remains 1.25. This bent line has been applied, and the resulting percentages have been smoothed and plotted in figure 24.

SOUTHERN BAVARIA GROUP.

This group of 7 Pinus silvestris and 1 Picea excelsa sections was cut for me by the kindness of Messrs. Klopfer and Konigen in Munich from logs in their yards. The trees had been cut in the winter of 1911-12 at Altotlinz, Ober Bayern, some 50 miles south, at a considerable altitude, in the northern valleys of the Alps. The rings in all these were clear and distinct and no doubtful cases were found except a very few near the center of two sections, which were omitted in the means; yet the cross-identification was not fully satisfactory. Sections numbered M 2, M 6, and M 8 in this group showed 1 to 2 entire discordances out of about 10 features in the last 60 years. The others agree fairly well. Possibly this condition results from the rugged and non-homogeneous region where they grew.

On page 116 will be found the means from 1848 to 1911. In these, M 6 and M 7 are extrapolated for about 12 years, and M 8 for 2. These means will be found plotted in figure 8. The curve shows apparently a very rapid decrease of growth with age. The correction line assumed is a line reading about 3.15 mm. in 1850, 2.10 mm. in 1860, then with decreasing slope reaching a nearly level line at 0.90 mm. between 1895 and 1911. The means have been reduced to percentages of this line and smoothed by Hann's formula and plotted in figure 24.