DEOEMBEE, 1914. MONTHLY WEATHER REVIEW. 671
(4) Made, H. Ueber den Druck in Gasen unter dem Einfluss atarker elektromotoriacher Kriifte. Sitzungsb., R. Akad. d. Wieaen- ach. Abt. IIa, Wien, 1898, 107: 708. Easchek, E. L Mache, E. Ueber den Druck im Funken. ibid., 1898, 107; Annalen d. Ph aik (Wied.), N. F., 3899, 68: 740. 15) Mach. E. & Weltrubskv. f. v. Ueber die Fornieu von Funken- weh& Sitzunib., 6. Akd.'!. Wie-aensch., Wien,-1878, 78: 551. (6) Wolff in Annalen d. Phyeik (Wied.), N. F., 1699, 69: 339. (7) Lummer. Ueber dieTheoriedes Kmllee. Schlesischeu Geeells. f. vaterl. Kultur, 11. Abt., 1905, 83. Jhrb. \8) Mach, E. L Gruss, G. 0 tische b%ersuchung der Funken- we len. Sitzungab., R. Akad. 8. Wiaseua., Abt.IIa, Wen, 1878, 78: 479.
(9) Dljrr, J. R. Ueber die Fernwirkung der Explosion am Stein- felde bei Wiener-Neuetadt (1912, Juni 7). Sitzungsb., K. Akad. d. We- sens., K1. Ha, Wien,. 1913, 1% O : 1683.
(10) Walter, B. (n Phys. Ztschr., 1902,8:168; also Hamburger wiwene. Anatalt-a, Jhrb. 1503, BO
. 3.
*', 3 ; ." - ,. *'j 1 2 t. THE PUCE OF FORESTRY AXONC) NATURAL SCIENCES.'
By HENRY 5. GRAVES, Chief, United States Forest Service.
[Extracts from an address delivered before the Washington Academy of Scicnres, Dec. 3, 1914.1
Forestry as a natural science deals wit.11 tahe forest as a community in which the individual trees influence one another and also influence the character and lifc of the community itself. As a comniunity the forest, has indi- vidual charac.ter and form. It has a definite life 1iist.oi.y; it grows, develops, matures, and propngatcs itself. Its form, development, and find total product inay be modi- fied by external influences. By.el)use it mtiy be gmatly injured, and the forest as H, living ent,ity may even be
destroyed. It responds equally to care, and niay be so molded. by skillful treatment as to produce n high quality of product and in greater amount and in a shorter t,iiue than if left to nature. The life history of this forest community vanes accordin to the species composing it,
of different a es are grou ed, the climatic and soil factors
The sim lest form of a forest c.ommuiiity is that coni-
When several species and trees of different ages occupy the same ground, the forni is more coniples, the crowns overla pin and the roots occupying different layers of the sol. 'fhus, for instance, when the ground is occupied with a mised stand of Douglas fir and hemlock, tho former requiring more light occupies the u per stor , and he-
strata of the soil. The hemlock, on the other hand, which is capable of growing under shade, occupies the under sto , and having shallow roots utilizes largely the top sox * * * In a forest there is altogether a different climate, a dif- ferent soil, and a different ground cover than outside of it. A forest cover does not allow all the precipitat.ion that falls over it to reach the ground. Part of the pre- cipitation remains on the crowns and is later evaporated back into the air. Another part, through openings in the cover, reaches the ground, while a third art runs down along the trunks to the base of the trees. &any and exact measurements have demonstrated that a forest cover interce ts from 15 to SO per cent of recipitation, accorrl-
forest, and other factors. Thus pine forests of the North intercept only about 30 per cent, spruce about 40 per cent, and fi nearly 60 per cent of the total precipitation that falls in the open. The amount that runs off along the trunks in some species is ver small-less than 1 per cent. In others-for instance, {eechbit is 5 per cent.
the density of the stand, t E e manner in which the trees
which affect t % e vigor an T; growth of the individual trees.
posed o P trees of one species and all of t,he same age.
cause of its deeper root system exten t; s to the r ower-lying
ing to t R e species of trees, density o P the stand, age of the
1 Reprinted from Journal, WE&. Acad. Ed., Jan. 19,1915,641-50.
Thus if a certain locality receives 50 inches of rain, the ground under the forest will receive onl 40, 30, or 20
from the totnl circulation of moisture over the area occu- pied by the forest. The forest cover, besides pre~eiit~iiig all of the precipitation from reaching the ground, simi- lmly keeps out li ht, heat, and wind. Under n forest
light chiate xiid a different relative humidity tlinn in the open. * * * The effect which trees in a stand have upon each 0 t h is not confined merely to changes in their external form and growt,li; it extends also to their internal struct,ure. The specific gravity of the wood, its composition, and the
differ in the same species and on the same soil an in the matonicd structure which determines its specific
same climate, according to the position which the tree occupies in the stand. Thus in a 100-year-old stand of spruce and fir bhe specific gravity of wood is greatest. in trees of the third crown class (intermediate trees). The ratio of the thick wall portion of the annual ring to the thin wall of the spring wood is nlso different in trees of
different crown classes. The difference in the size of the tracheids, in trees of different crown classes, may be so reat that in one tracheid of B dominant tree there may f e placed three tracheid cclls of a suppressed tree. The amount of lignin per unit of weight is greater in domi- nant trees than in suppressed trees. * * * Forestry, unlike horticulture or a iculture, deals with wild lants scarcely modified by cu ff' tivation. Trees arc
also !&-lived plants; from the origin of a forest stand to its maturity there may pass more than a century. Foresters therefore operate over long periods of time. They must also den1 with vast areas; the soil under the forest is ns a rule unchanged by cultivation, and most of the cultural operations applicable in arboriculture or
agricblture are entirely impracticable in forestry. For- est,s, therefore, are largely the product of nriture, the re- sult of the free lay of natural forces. Since the foresters had to deal wit.[ natural plants which grew under natural conditions, they early learned to study and use the naturitl forces affecting forest growth. In nature the least change in the topogritpliy, exposure, or depth of soil, etc, means n change in t.he composition of the forest, in its density, in the charactcr of t,hc ground cover, and so on.
As a result of his observat,ions the forester has developed definite laws of forest distribut.ion. The forests in the diffnreiit regioils of the countr;p have been divided into natural typcs wit.h corresponding ty es of climate and site. These iiotural forest types, whici, by the way, were also developed long before the modern conce tion of lant formations came to light, have been laig at the foundation of nearly all of the practical work in the woods. A forest type became the silvicultural unit, which has the
same physical conditions of growth throughout, and therefore requires the same method of treatment. The manlier of rowth and the met,hocl of nt~turd re ener&
same type no imitter where it occuis.
After the relation between a certain natural type of forest and the climate and topography of a region has been established, the forest growth becomes the living espression of the climatic and physical factors of the locality. Similarly, with B given type of climate and locality it is possible for the forester to conceive the t of forest which would grow there naturally. The sp" OF
ester, therefore, ma speak of the climate of the beech
pine forest. Thus, if in China, which may lack weather observations, we h d a beech forest similar to one found
inches. Thus 10, 20, and 30 inches wi 9 be withdrawn
cover, therefore, t P iere is altogether a different heat and
tion, oncc f ercloped for n forest t,ype, hold true f or the
forest of the Engemann 9 spruce forest, of the yellow-
672 MONTHLY WEATHER REVIEW. DECEMBER, 1914
1983-81.. ................................... -1 .... ./. .........
1885-86 ...................................... !..........I..... -4 ................................... .......... 1 M ..
1886-87 ...................................... 1 -5 188748.
lS90-81.. ........................................................ .................................... G
............................................. --s I
1SsIwo.
1891-92.. 1892-9c..
1894-85.. ........................................................ 1897-9s..
1900-1901. 1803-04.. .................................... -S -5 1904-05.. .................................... -4 ..........
190s-09.. ,._I
.I: : : : :
...................................................................
9 .....................................
t i
1s!xi44.. .................................... I: .........
.................................................................
.......................................................
.....................................................
in northern New York, we can be fairly certain of the climatic similarities of the two regions. More than that, a type of virgin forest growth may serve as a better indi- cation of the climate of a particular locality than me- teorological records covering a short number of years. A forest which has grown on the same ground for many generations is the result not of any esceptional climatic cycle, but is the product of the average climatic condi- tions that have prevailed in that re 'on for a lon time.
factor, but is the product of all the climatic and physical factors together. Similarly, the use of the natural forest types for determinin the otential capacity of the land
more and more appreciated. When the climatic char- acteristics of a certain type of forest, for instance, those of Engelmann spruce in the Rocky Mountains, is thor- oughly established, the potential capacity of the land occupied by it for agriculture, grazing, or other pur- poses is also large1 determined.
growth naturally brought out facts with regard to the effect of forests upon climate, soil, and other physical factors and led to the development of a special branch of meteorolo y, known as forest meteorology, in which
are some phases in forest meteorology which still allow mom for disagreement, some relationships established b foresters are widely accepted. One of these is the e h ect which forests have upon local climate, especially that of the area they occupy and of contiguous areas. Every farmer who plants a windbreak knows and takes advantage of this influence. Another relation is that between the forest and the circulation of water on and in the ground, a relation which plays such an important part in the regimen of streams. Still a third one, as yet beyond the possibility of absolute roof, is the effect of
upon the humidity and temperature of far-distant regions lying in their lee. * * *
It expresses not only the result o P one single cfmatic
occupied by them B E or di erent purposes, is becoming
Observations o 9 the effect of climate upon forest
the foresters % ave taken a prominent part. While there
forests in level countries, in the pat E of prevailing winds,
. E' (7 L '
-; 1 ..........
I -4
-6
.............................. ....................
;I .......... ........ .................... I ..........
I --
.......... I.. ........ ..........I .......... I .......... 5
-s ......... -s .......... -7 ..........
4 ..........
WHY SO35 WINTERS ARE WARX AND OTHERS COLD IN THE EASTERN UNITED STATES.
1911-12..... ................................. 5 1912-13 ...................................... 4
.... .
By W. J. HUYPHBEYB, Professor of Meteorological Phyaica.
[Dated Weather Bureau, Washington, Feb. 1,1915.1
INTRODUCTION.
As ever one knows, no two winters are exactly. alike.
eastern United States that here some winters are much colder than the average while others are exceptionally mild. Of course, many other laces ex erience similar
their seasons, and to each there necesiily%elongs an interesting study of how these differences occur and why. In the present paper, however, only exce tional wint.ers
Even a s K ort memory will convince one living in the
differences in the severity, or, i P one pre ers, eniality of
in the eastern United States will be consi t; ered.
LIST OF ABNORMAL WINTERS.
An examination of the climatological records shows that beginning with December, 1880, the earliest date for which we have sufficient and convenient data for the resent study, the enstern United States has had a num-
ger both of exce tionally mild and of exceedingly cold winter months. &he more pronounced of these are listed
-s .................... 9 1 ..........I
5
in Table 1, in which the numbers give, rou hly, each the
normal.
TABLE l.-EzcesSive monthly tern eralure dtpartwes in the eaatern United
avera e temperature de arture for the mont % in question, over t % e eastern Unite B States, from the corresponding
{h.%S.
__--
ISSBSl ............................... lllS2 ............................... 15S4-S ............................... lS9-W ............................... 1903-04 ............................... 1912-13.. .............................
OF. 1 ~1 .. .................................... ........ 1881-82.. .................................... ..........
Cold .......... Warm ......... Disagreement. Warm .............. do ......... Agrsement. Cold .......... Cold .......... Do. Warm ......... Wann ......... Do. Cold .......... Cold .......... Do. Wann ......... I Iyak;icient
(?!.
PREPONDERANCE OF LOCAL OVER QENERAL CAUSES.
If we omit isolated months and consider only entire winter seasons, i t will appear that usually the tempera- ture departure of the eastern United States has been of the same sign as that of the whole world, which in turn seems to depend upon the combined influence of sun spots and volcanic dust (1). This general agreement shown in Table 2, it should be remembered, is between the annual temperature departure of the world as a whole and the winter temperature departure of only the eastern United States. Therefore, agreements and disagreements in their signs, since the periods are not the same and since the local seasonal departure often is from 10 to 20 fold that of the world-wide annual departure, probably have but little meaning. Nevertheless, if the number ot cases were sufficient.ly large there probably would be rather more instances where the signs of the departures were the same than where they were different : hence, though the period covered is too short satisfactorily to test even this point, it seems only fair to give the comparison table for what- ever, if anything, it may be worth.
TABLE 2.-Comparison of seasonal local (winter, eastern United States) and annual world-wide temperature departu~es.
On its face this table indicates decided1 more agree- ments than disagreements, but, as alrea d y stated, the local winter temperature departures under consideration are so man times greater than the world-wide annual
having their influence, clear1 can not be the chief cause departures t Tl at the causes of the latter, though, of course,
of the former. Neither do t E e former, pertaining to but