186 MONTHLY WEATHER REVIEW MAY, 1928
1028
Fob. 21 Feb. 21 Mar. 17 Mar. 18
Mar.19
the value T= 1.00 (according to Linke) ; here 1.932 calories per minute per square centimeter is taken as the solar constant and also for the purpose of calculating the t u r bidity factor T.
Solar radiation, Arosa, Surifzerland
0
11:Ol a. m ________________ 30.8 (1.6) 31 1.69 1.64 1.17 11:52a.m ________________ 32.2 ________ ________ 1.59 1.65 1.21 12:M p.m ________________ 41.0 (li;i 30 1.61 1.69 1.28 1l:Ua. m ________________ 421 a4 1.83 1.69 1.20 12:CQp.m ________________ 426 2 0 32 1.69 1.69 1.37
Until now the value of 1.63 calories was vouched for only a t elevations above 3,000 meters. The turbidity of the air, especially in 80 far as relates to the dates given above, was very moderate; the normal March values of Tare as follows: Arosa, 1.5; Davos, 1.8; Potsdam, 2.2;
and Frankfort on the Main, 3.5. At 1.4 mm. the deter- minative water vapor content was very low; in good agreement with this was the value e= 1.5 mm. at Arosa at the minimum of the turbidity factor, T= 1.13, on the midwinter date of January 15, 1925. Even in case the values J-J' for the forenoon of March 18, 1928, are extrapolated to vacuous space there results no. necessity of a cause for the high radiation values outside of the high transmissiveness of the atmosphere. Does a higher value of the solar constant play a Ale in the marked solar activity? Whatever may be the case, it will be interesting to await values for the spring of this year obtained a t other pomts and especially Abbot's values for the solar constant.2-Trunshted by W. W. Reed.
GROWTH OF TREES IN THE FOREST OF DEAN IN RELATION TO RAINFALL
[Reprinted from Meteorological Magazine, March, 18281
Mr. E. G. Burtt has kindly supplied several series of measurements of the annual rings of wth of trees in
given by a yew, which grew on a southwest slope over- looking Lower Sondley. The tree was cut in the winter of 1922-23, and proved to be 200 years old. The indi- vidual measurementa are given in Table 1, and smoothed values constructed by taking overlappin five yearly
will be seen that the tree grew very slowly a t the begin- ning and end of its existence and more rapidly in middle age. There are four periods of most rapid growth; the h t and most important occurred from about 1780 to
1800, with a maximum from 1786 t,o 1792, and tho sec-
the Forest of Dean. The best and r-0 ongest series was
totals are shown in the uppermost curve of k igure 1. It
forta an at sly the Astro hysical Obssrvstory of the Smithsonkn Institution has already contributed the &AI eonstant values for the d a h In question to the Weather Bureeu for publication on the Daily Weather Maps. The values am 8.3 follows:
Feb. 21 ________________________________________-- 1.089 satisfactory minus. Mar. 17 ________________________________________-- 1.m aatioPlotory minus. Mar. 18 ________________________________________-- 1.844 satiolbctory minun. Mar. 19 ________________________________________-- 1.0% SatMactory minus. -Ed.
ond reached its maximum in 1829 to 1830. The third maximum extended from about 1861 to 1878, but is not very striking; on the other hand, the fourth maximum,
which comes at 1899 to 1900, is remarkably sharp and definite. It will bo noticed that the lengths of the inter- vals between these maxima, about 40, 40, and 30 years respectively, give an average of 36-37 years, which is very near that assigned to the Briickner cycle.
FIQ. I
Measurements of two oak trees are given, both of which grew on Staple Edge Hill and were cut about 1921.
The individual measurements are not reproduced here, but the fi ures smoothed by forming five-yearly totals are
ments taken at right angles on the same tree-an ex- ceptionally well formed r o o t 9 A being along a line due west from the center and 9B along a line due north. An
attempt had been made at some time to burn the stump, and the outer 40 mm., re resenting about 42 years' growth, were charred. It w& be noticed that from 1830
to 1864 the tree grew somewhat more rapidly on the west than on the north side, but that from 1864 to 1883 this condition was reversed, growth being more rapid on the north side of the trunk. The curve labeled 10 rep- resents the second oak tree, which showed no signs of
burning. The two curves 9A and 9B are obviously closely related; No. 10 is fairly similar, but the pro- nounced maximum just before 1840 is barely represented, and the period of most rapid growth occurred instead about 1860. The most curious point is that these records of oak trees show very little similarity with that of the yew which grew only a short distance away. This is partly due to the much lesser age of the oaks, not one of which was 100 years old, so that the period of slow growth at the beginning of their existence coincides with the full maturity of the yew, and in fact with one of its periods of maximum. It is only when we examine the curves in detail that we can see points of resemblance, in particular the rapid increase of growth rate about 1860
and the general slow growth from 1880 to 1893. There is a distinct suggestion that the oaks responded more rapidly to changes of weather than the yew, for the curves 9 and 10 are far more irregular than the upper- most curve. The pronounced maximum at 1900 on the latter shows itself as a double m&yimum on both oak trees, and similarly the s m d minimum of 1865 on the curve for the yew becomes much more important in the oaks.
shown in B igure 1. Curves 9A and 9B are from measure-
MAY, 1928
2 0 3. 5 bo 3.0 4.5 3.0 2 0 2 0
3.0 2. 0 2.0 3.0 2. 0 1.5 2 0 3.0
MONTHLY WEATHER REVIEW
1 2 3
-~-
___________ 1.0 2.0 3.0 3. 5 3.0 4.0 3.0 4.0 4.5 3.5 4.5 3.5 2.5 1.5 1.0 2.0 3.0 3.0 3.0 3.0 2.0 2.0 20 3.0 1.5 2.5 2. 0 1.5 1.5 2.5 2.0
3.0
187
1.0 2.5 2 5
4.5 4 0 2 0 1.5 2.5 3.0 20 20 2 0 2.5 2.0 2. 5
3.5
. - - - -
TABLE l.-Growth of yew tree in millimeters
5 8 7
---
1.0 1.0 !A5 2 0 3.0 3.0
LO 4 5 4 5 40 %O 2.5 1.5 3.0 3.0 3.6 3.5 3.0 2 5 2.5 1.0 1.5 2.5 2 5 2.5 2 0 2.0 2 0 3.0 3.6
as 40
- - - - - - - - - - -.
Treegrowth,mm.-
Rainfall, percant.-.
-
4
-
1.0 2 0 2.0 4.0 40 3.5 2.5 2 0 3.0 2. 5 2 5 2.0 2.0
2. 0 2 0 2. 0
____ -
18% 1 m - l* I&@- 1835 1845 1.955 181
----
32 28 21 20.5
----
95 101 I Os 86
1sa6- 1695
21
law- 1889
1025
-
8
-
2 0
20 40 3.0 5.0 3.0 2 5 3.0 4 0 2 5 20 20 2 0 2.0 2 0 4 0
-
1886. 1906- 1w 191s
---
a8 (14)
law- 1900- 1869 leoB
---
92.5 Os
9
2.0 2. 5 3.0
40 3.0 2 5 2 5 40 3.5 2 0
2.0 2 0 20 20 4 0
a. s
.-__- -
Total growth 1823-1732, 8 mm., 1732-1742. 9 mm. Total growth 1903-1912, 14 mm., 1913-1922, 14 mm.
Of the beech trees, Nos. 5 and, 6 grew on the Blaize Bailey ridge and No. 11 grew near the yew tree; the dates of felling are not known, but were probably between 1900 and 1910. The two records 6A and 6B are from measurements along two lines a t right angles-on the same tree, but the actual directions are not speafied. Since the dates of felling were not known exact.ly, it was neces-
sary to fit the curves together from intnnsic evidence ody.
This was not difficult so long as only the three beech trees were considered; the correlation actually adopted seems to be the only possible one. When it came to fixing the age of the trees absolutely, by reference to the yew and oaks of which the dates of felling are known, it was a
different matter, and the dating adopted in drawing Figure 1 is to be regarded as something of a
the oaks and the yew, t h t beech trees grew s owly a t the beginning and end of their exlstence, whde the response to changes of climate seems to have been more rapid than that of the yew, but perhaps not qmte so rapid as that of the oaks.
For comparison between the rate of tree-growth and the amount of rainfall, Dr. J. Glasspoole has been good enough to calculate a series of rainfall values for the Forest of Dean extending from 1820 to 1920, expresaed as
a percentage of the normal for the 35 years 1881 to 1915.
A comparison of these figures with the.annua1 growth. of the yew in Table 1 shows that there is httle if any relahon between the growth in any one year and the rainfall in that year. When we smooth the data over a number of years, there are some indications that heavy rainfall is lnimical to the growth of the yew, but with the oak and the beech the relation is still indefinite. The rainfall data, smooth6tl by forming overlapping 10-year means, are shown in the lowest. curve of pigwe 1 ; following the model of the well-known American investigations into the relation between tree-growth and ramfall the curve
$ess. Like
has been shifted to the left, in order to compare the tree growth in any year with the rainfall durin the previous 10 years. Thus the point where the rainfal 7 curve crosses the vertical line for 1830 shows the rainfall of the years
1821 to 1830, which was 98 per cent of normal.
TABLE 2.-Comparison of growth of yew tree with rainfall
Os
1976- 1885
114
The period of rather rapid growth of the yew about 1830 comes at a time when the rainfall curve is low, but the minimum from 1851 to 1859 follows the maximum of the rainfall curve by about 10 years. The poorly devel- oped period of maximum growth from 1861 to 1870 fits in fair1 well with the minimum of the same years on the rainfdcurve, but the outstanding maximum shown by the latter about 1880 to 1883 is only represented by a
slight minimum on the curve of tree-growth. On the other hand the pronounced maximum growth about 1900
agrees very well with the minimum on the rainfall curve. The opposition is also shown in Table 2, where the total growth of the yew in successive periods of 10 years is
compared with the rainfall 6 years earlier. The most notable feature of this table is that, excluding the years
1906 to 1915, when the slow growth of the tree may be attributed to old age, the slowest growth, 19 millimeters in 1876 to 1885, corresponds with the decade 1870 to 1879, which was by far the rainiest, while the two periods of most rapid growth, 1826 to 1835 and 1896 to 1905,
correspond with the two decades of least rainfall. There are no available records for the Forest of Dean previous to 1820, and a comparison of the growth of the yew from
1750 to 1820 with Doctor Glasspooles fi ures for the
zine for February, failed to show any definite relationship. If the hypothesis that the yew grew best in dry weather is correct, we should infer that in the Forest of Dean the years 1803 to 1813 were rainy and the years 1780 to 1790 dry; it would be interestin to know if local non-
eral results of the comparison are not very convincing, however, and do not make it probable that we shall ever be able to write the history of our rainfall from the rings of our trees, as has been done so successfully in the west of America, even if we can find trees of suflicient age.
whole of England, published in the Neteoro 70 gical Hug&-
instrumental records confirm or (B isprove this. The gen-