NOVEMBER, 1930 MONTHLY WEATHER REVIEW 455
(e) That, while division and section mean monthly
temperatures are of some value for purposes of comparison in more or less level areas, they are of little use for that
purpose in many rugged or mountainous regions. How-
ever, mean monthly temperatures in such rugged regions,
if arranged and averaged by elevations, may serve many useful purposes, and tend to establish practically the effect of altitude on temperature, just as in the more level areas
north to south division mean temperatures establish the
variation due to latitude.
For instance, in the published climatological data for Colorado for A ril, 1927, there is no separation of the
stations are arranged alphabetically in one list. The
mean temperature for the entire State was computed from the several mean temperatures in this list by averaging
them in one operation, and was found to be 44.2.
If, however, we arrange stations and compute mean
temperatures by altitudes from lowest to highest in sev-
eral zones, say of 1,000 feet each, we have, beginning with
the lowest zone, results as follows: 3,000 to 4,000 feet, 6 stations, mean temperature, 52.1; 4,000 to 5,000 feet,
16 stations, mean temperature, 49.9; 5,000 to 6,000 feet,
13 stations, mean temperature, 48.6; 6,000 to 7,000 feet, 14 stations, mean temperature, 44.5; 7,000 to 8,000 feet,
8 stations, mean temperature, 40.3; 8,000 to 9,000 feet, 11
stations, mean temperature, 36.0; 9,000 to 10,000 feet, 4
stations, mean temperature, 35.5; 10,000 feet and higher,
4 stations, mean temperature, 33.2. This arrangement and averaging shows a more or less
gradual drop in mean temperature from the lower to the
higher zones. The average altitude computed from the
elevations of the entire number of stations in the list is
State into sm a i er divisions, but cooperative and other
6,416 feet, which falls in the 6,000 to 7,000 foot zone, the mean temperature of which, as obtained above, is 44.5,
only 0.3 higher than the mean temperature for the State
(44.2) as printed. Similar results have been secured
from the data for other mountain States.
(d ) That, while the demand for climatological data is
constantly growing, and while inquiries are ever increas- ing in variety, response to which requires more and more
time for special compilation, the limits of the publication
have remained practically constant for more than a decade.
The need for more detailed data on storm damage alone would frequently justify the extension of the printed matter by practically a page; and if we could insert in
this publication data to answer inquiries regarding fre-
quency of rainfalls and snowfalls of stated amounts, river stages and flood conditions, more complete information
as to the effect of weather on crops, etc., still another page
would be none too much. Such questions as those briefly discussed in this paper,
together with many others, some general, some pertinent
to individual sections, are the problems of the Weather Bureau section director in serving the public interest.
Their consideration, it is believed, should receive the
attention of more than the individual official in his section;
and in conclusion the writer begs leave to express the hope that at some time in the future i t may be found
practicable for the officials in charge of the climatological work of the bureau, both at the central office and in the
field, to congregate from time to time to discuss in body these and similar questions, and to provide as far as prac-
ticable uniform and increasingly effectual methods of
handling and publishing these valuable records of the
cooperative climatological service.
FOREST-TREE DISEASES CAUSED BY METEOROLOGICAL CONDITIONS 
By ERNEST E. HUBERT, Professor of Forestry
[School of Forestry, University of Idsho]
When crops are poor, when epidemics of human dis- ease are prevalent, or when forest l2es rage over a wide
territory, we are constantly reminded Its the weather. The weather appears to be held responsible for many
things, including rheumatism and the irregularities in the yearly growth of trees. Now come the forest path-
ologists to fill the cup to overflowing by stating quite calmly that meteorological conditions are responsible for
a considerable number of important tree diseases. For-
tunately, many of these diseases are of minor importance
economically and do not greatly affect the life of a stand
of timber. Others, however, cause considerable loss.
In a discussion of tree diseases, it is always helpful to
group them under two main heads-(1) diseases caused by organic agencies such as fungi and mistletoes and
(2) diseases caused by physiogenic agencies such as heat, frost, wind, and similar physical causes. The physiogenic
diseases include all causes of disease which are produced
by various atmospheric changes and disturbances, as fol- lows: Sunscald, drought, wilting, frost cracks, frost heav-
ing, frost bite, wind breakage, wind throw, wind deforma-
tion, red belt, sun scorch, too much or too little light, lightning injury, ice injury (sleet storms), snow break-
age, snow smothering, snow heating, subsnow fungi, root suffocation (too much rain), gas injury, and dust injury.
FROST INJURY
Much has already been written on the cause and con-
trol of frost injury brought about by low temperature.
I Presented before the American Meteorologic81 Society, Psciflc Division of the A. A. A. 8.. Eugene, Oreg., June 20,1930.
3200-1-2
In the literature are to be found several types of frost
injury designated by various terms. Early and late frost injury, discoloration, wrinkling, slitting of leaves, and
frost cracks are common injuries which result from the
effects of direct freezing. Other types of injury such as red belt and a closely related one which may be aptly termed sun scorch or sun burn appear to be caused
primarily by low temperatures but require the action of meteorological factors other than frost to bring about
actual damage and the accompanying symptoms. Frost injury in one form or another is fairly common
in all regions where the temperatures fall below the freez- ing point of water. In the colder climates severe injury
frequently occurs in seedling stock grown in forest nur-
series and to transplanted stock. In the forested regions certain areas are known as frost pockets or frost centers
in which frost injury is apparently more prevalent than in the adjacent areas. Topography and exposure are fac-
tors of importance which may account for such areas.
Sun scorch and red-belt injury are confined to the conif- erous forests and are most commonly, if not exclusively,
reported occurring in the western coniferous belt. Wilting takes place after severe frost injury and is fol-
lowed by discoloration of the leaves and later on by a
water-soaked appearance of the tissues. In some species
the young bark turns a dark color. Tender tips and
stems and young leaves are most susceptible and for this reason nursery stock often suffers severely. Another common symptom of frost injury is the well-
known frost crack or frost split which occurs in the trunks of some of our forest and ornamental trees. These radial
456 MONTHLY WEATHER REVIEW NOVEMBER, 1930
cracks are usually found in the lower trunks, originating in the hollows of the root collar between the root spurs and extending several feet up the tree. They usually
show considerable callus growth where healing of this typezof wound is in progress. Repeated opening of the
healed crack by subsequent frost and wind action forms
on either side of the crack large callus growths which pro-
ject some distance out from the normal circumference of the trunk and are often called frost ribs: These cracks
also extend into the heartwood for considerable distances
and render the lower trunk useless for high-grade lumber or timber. Circular cracks or frost shakes are formed in some trees by low temperatures. Gummosis and resinosis
are signs accompanying such injuries.
Since the younger and more delicate tissues are most
susceptible t? low temperatures, injury to leaders and to branch tips is of common occurrence in the frost belts.
The resulting wiltmg and die-back are also symptoms of fungous diseases and care must be exercised in determin- ing the original agency causlng the prime injury. The
tips of young trees in our western conifer forests fre-
quently suffer from a peculiar type of frost or winter injury. The leader and one to several whorls of branches
down from the top turn a bright wine red soon after bright sunlight followed a cold snap. The whorls on the
lower trunk which were buried in snow or otherwise
protected from rapid thawing by sunlight remain green and the branches above snow level, or those exposed to
the sun, become reddish in color. The tips and discolored branches die, causing deformed tops. In severe case
the young growth is killed back until the tree has developed an abnormal bushy form.
Temperatures below the freezing point of water (Oo
Centigrade or 32 Fahrenheit) are indicated in the use
of the term frost as an agency of tree diseases. Late frosts in the spring injure tender growing tissues while early frosts in the fall injure older plant tissues before
they have become fully prepared for winter dormancy.
Very susceptible young tissues may be injured at tem- peratures slightly above 3 2 O F. When the tissues of leaves and young stems are frosted
water is either withdrawn into the intercellular spaces
where ice crystals are formed, or the ice is formed partly
or wholly within the cells. In either case water is ex-
tracted from the protoplasm and wilting takes place due
to the reduced turgidity of the cells. If thawing is brought about slowly the water is reabsorbed by the cells without resulting damage and the plant again resumes
its erect position. There are differences of opinion as to when and how frost action may prove fatal to the plant. Hartig (l), discussing the various angles of this problem,
points out that the death of a plant by frost during winter
bears a close resemblance to the effects of drought. Thus red-belt injury may be caused by a sudden thawing of the leaves in the crown accompanied by transpiration
which removes more moisture from the leaves than can
he supplied by the frozen trunk and roots. If the water deficiency in the frozen cells exceeds a certain limit and
this amount can not be replaced by the adjacent tissues or
supplied by the roots, the tissues die. Neger (2) has found that sunlight plays an important part in the revival
.of chlorophyll tissue which has been frozen. Conifers subjected to low temperatures revive fully if allowed to recover slowly in darkness, but develop discolored needles
and cast them, in the case of spruce, if the frozen plants
are allowed to thaw out in full sunlight. Photosynthetic activity during the time when little water is available and the cell sap is highly concentrated may bring about chemical changes which result in the death of the proto-
plasm. Hartig indicates that drought during open sunny
winters when the roots are frozen accounts for consider- able winter-killing. The conclusion is that death due to
frost takes place at the time of thawing even in such cases, for it is upon the return of temperatures favorable to
metabolism that the cells become active and die from
lack of sufficient water.
RED BELT
In typical red belt there is a tendency for the older needles to be cast first and for t,he youngest needles to remainuninjured and attached to the tree. This is partic-
ularly noticeable in such species as Douglas fir (Psewlot- suga taxifolin) and Englemann spruce (Picea engelma.nii), where all the needle,s but the youngest are cast and in
addition the buds are often killed. In such cases the char- acteristic red crown is missing. Red belt is most pro-
nounced on trees exposed to the east, south, and west, and on t,hose borderin the stands or on isolated trees.
There is a marked ban%ing or grouping shown by the dis- colored trees which seems to follow the conforma;tions of
the topography, in some cases almost parallelmg the contour lines (1, 3, 4, 5). These bands may be quite regular or irregular and may vary in width. Again, as in
tmhe 1924 winter injury to conifers in the Montana, Idaho, Washington, and British Columbia areas, the discolorn- tion was fairly general with no distinct banding in evi-
dence. Whenever the lower branches of red belt, winter- kill, or sun scorch trees are buried in the snow they usually
escape injury and bear a full set of healthy green needles. With regard to gross symptoms and primary agencies the
two diseases known as red belt and wmterkill may well be identical.
The syniptoms of another type of winter disease known
as sun scorch, sun burn, and sun scald are somewhat different from the above. Discoloration and death of the
needles and tops, sometimes the entire tree, occurs on exposed trees, particularly the smaller isolat,ed trees
bordering a dense stand or growing along the edges of
highways and railroad rights of way. The color is a bright wine red to reddish brown depending upon the
species, and the discolored needles usually cling to the branch for a considerable period after injury has taken
place. The lower crowns or individual branches, p ~o -
tected by snow banks, snow coverings or by neighbonng trees, remain green. This presentas a characteristic ap-
pearance-a dead and discolored upper crown with a green lower crown. The south, southeast, or southwest sides of
aff ecbed trees show the greatest amount of discoloration and injury and tre,es growing in situations exposed to sun-
light show the most severe damage. Many of the white
firs (Abies grand.is) aud western red cedars (Thuja plicata) show a dwarfed or bunchy type of growth due to thekilling
of the leader and some of the upper branches. Examina-
tion of the stems of sun-scorched conifers in the region
helow and iminediately above the edge of the dead tissue
disclosed no signs of frost rings in the annual rings of the
wood.
It is believed that, in all the types included under this group of physiogenic diseases, the direct cause of death
is a shortage of water making itself felt in the needle or leaf tissues. In drought it may be the rapid lowering of the soil water table, a porous and shallow soil, injury to the root system, too rapid transpiration, prolonged hot,
dry periods in the growing season, sudden exposure b thinning or removal of trees. In the case of winter&
and red belt, death is apparently caused by excessive
transpiration of the needles during warm, sunny periods in the winter when the ground, roots, and trunk of the
NOVEMBER, 1930 MONTHLY WEATHER REVIEW 457
tree are frozen. Such sudden warm periods or chinooh,
as they are known in the northwest, usually follow a
period of unusually low temperatures. Durin this warm
activity and sufficient transpiration takes place to exhaust
the available water. In this way the water column is
broken since no water is obtainable from the frozen branch and trunk and the needles are unable to continue
their normal activity and soon die.
Bright sunlight and rising temperatures, following a
sudden period of low temperature, appear to be responsi- ble for the injury known as sun scorch and the character-
istic symptoms help to bear out this assumption. Neger
(2) states that it is not so much the freezing action that
causes the damage as it is the action of direct sunlight
in rapid thawing and activating the photosynthetic cells of the needles. He conducted some interesting freezing
experiments with spruce branches and found that the
frozen branches which were revived in the direct sunlight developed discolored needles which were later shed, while
those branches revived in a dark chamber recovered completely. Similar experiments were conducted by
myself on branches of Douglas fir, lodgepole pine, yellow pine, western white pine, B-estern hemlock, lowland white
fir, concolor fir, Engelmann spruce, western red cedar, western larch, and jack pine. Two sets of branches of
the above species were placed in an electric refrigerator
a t a minimum temperature of 18 F. for 16 hours. At
the end of this period one set of branches was placed in the direct sunlight, their stems in water, while the other
set, also supplied with water, was placed in a darkened cupboard. At the end of a 12-hour period the set ex-
posed to sunlight showed a large number, nearly 50 per cent, of its needles discolored a light reddish brown and
a casting of the injured needles had already begun on
the Douglas fir, spruce, and larch branches. The set which thawed out in darkness under ordinary room tem-
peratures remained reen and healthy in appearance. The bronzing of froadleaf foliage (6) niay have its
origin in a deficiency of water and it is common during dry seasons to find the leaves of mountain alder (L41nu8
tenuifolia), serviceberry (Amelanchier alnijolia), and occasionally of birches (Betula spp.) showing typical
reddish brown discolorations in the leaf areas between the principal veins, known as the intercostal areas.
The direct cause of death in all such cases where frost and other agencies such as sunlight and rapidly rising
temperatures seem to be coordinated, is the subject of
much discourse. Is it the freezing or the formation of
ice crystals that kills? Or is it the withdrawal of neces- sary water or a disturbance of the chemical balance within
the frozen cell that results in injury or death? Abbe (7) ably summarizes the present concept regarding these
questions as follows:
As the temperature of the plant cools the water exuding from the
individual cells leaves a more condensed sap behind and the inter-
cellular spaces are filled with purer water. Owing to capillary phenomena this water is not easily frozen until it has been cooled
several degrees below the freezing point, and then its temperature suddenly rises to 32 F., as in the ordinary experimentation of the
physical laboratory. The water within the cells is of course not yet frozen, being a more condensed sap, whose freezing point is
usually lower than that of pure water. If now the temperature falls still lower, the ice cools, and eventually the sap within the cell is not more than sufficient to fill up the space formerly occupied
by the water t b t exuded. I f now the plant thaws out, the great
mass of intercellular mater escapes by transpiration. A little niay go back into the cells, but this is a small percentage and oftentimes none. Further- more, a chemical change takes place in the cells by the excretion
of pure water, and the cell sap that is left behind constitutes a new chemical compound. Such cells now change their character and
period the heat and sunlight stimulate the 5 eaves into
The plant wilts by the rapid loss of this water.
their relation to the growth of the plant. Many of the excrescences aiid the diseases formerly supposed to be due to bacteria, or fungi, or parasites are found to be due to the chemical changes that have
taken place within the cells in consequence of freezing. Thus Hartig shows that the frost krebs, or excrescence on treee, is a growth due to the effort of the lant to get rid of or cover up the dead cells produced by frost. &hen a frozen plant is young and
tender and its leaves immature, the exudation through its tender cell walls may lie directly on the outside of the cuticle, but as the cuticle hardens in the mature plant, and the development of sto-
mata becomes more complete, the greater part of the exuded water and its resulting ice is in the intercellular spaces. When the frozen plant is thawed out and evaporation is rapid, the loss of water either from the surface of the tender plant or through the
stomata of the mature plant is much more rapid than under normal conditions and the plant wilts, but when there is no evaporation, the sap has time to return into t,he cells, and the wilting is not so
severe. Therefore it is proper to say that the injury is not done by the more or less rapid thawing, but by the more or less rapid evapo- ration that accompanies the thawing. If similar plants are thawed
out under warm aiid cold water, respectively, the rate of thawing has no influence on ita health, as was shown by Sachs long ago.
It is now seen that this is because in both these cases there is no special chance for evaporation, and the sap was able to go back into the cells; the contrary occurs when the plant thaws in the open
air.
EFFECT OF HEAT
High temperatures cause wilting and heat lesions in
seedlings and transplants, usually resulting in death; and,
furthermore, may kill tender, frozen, or exposed young bark tissues causing a canker formation on the trunk, limb crotches, or larger limbs. The conditions, other
than temperature, surrounding the plant a t the time of injury are important with respect to the amount of
damage caused. Heat cankers or bark scorch may be produced on the southwest sides of tree trunks when such trees are suddenly released from a dense shaded stand
through logging operations, openings made for roads, highways, rights of way, fire lanes, or by the death of
neighboring trees. These injuries, if severe, may girdle the tree, otherwise they form infection courts for the
entrance of wood-inhabiting fungi. The color of the
soil very markedly controls the damage caused by the
high temperatures of direct sunlight. The darker soils, particularly the fire swept, charcoal covered soils, due to their high and rapid absorption of heat cause death to
seedlings growing on them. Hartley (3)) specifying measures to prevent stem lesions or whitespot injury of
seedlings due to heat, says Soil with loose texture or dark surface is presumed most likely to overheat a t the surface.
A record, made by Forest Service investigators a t the Wind River Valley Experiment Station, Washington, of seedling survival on two areas-one having ti mineral soil,
the other a black charcoal surface resulting from fire-
showed tt surface soil temperature of 143 F. and a loss of 100 per cent of t8he seedlings in three days time, while on
the yellow soil the temperature reached 125 F. with but
a 16 per cent loss of seedlings. Neger (2, p. 25) states that spruce and pine seedlings can bear a maximum
te,mperature of 54 C. without serious injury. Both broadleaf and coniferous trees are subject to this
type of dise,ase. The more tolerant species, those pos- sessing thin bark and those growing in moist sites, when
exposed to sunlight, suffer severely. The most common examples of bark scorch and heat canker are to be found
on orchard, shade and orntbmental trees. Of the shade trees the maples, birches and beeches appear to be quite susceptible to this injury. Among the conifers, the white
pines, certain spruces, Douglas fir and the true firs are
sensitive to heat when the young tender bark becomes exposed to sunlight. The primary cause of injury in this type of disease is
the high temperatures affecting young, tender tissues.
458 MONTHLY WEA
Whether these high temperatures cause death of the tissues by Billing or inactivating the rotoplasni in the
the literature on the subject. It would seem that the
lowering of the available water supply to a critical point through dessication would be a very important factor in
reducing the resistance of the younger bark tissues to the
injurious action of overheating. The overheating of
leaves when a very high relative humidity is present,
according to Neger (2, p. 24), results in a defoliation which is frequently more pronounced within the crown than on
the outer parts. Heald (8, p. 174) is of the opinion that winter injury is
probably a more common cause of canker on both fruit and forest trees than the high temperatures due to bright
sunlight. He states, however, that sun scald of some thin barked trees results from overheatins during the
intense sunshine and high temperatures of midsummer, coupled with a drying out of the tissues. A t8ype of sun
scald called winter sun scald is due to a combination of
freezing temperatures followed by exposure of the frozen tissues to direct sunlight of sufficient intensity to cause
injury .
cells or by a form of dessication is not c 7 early indicated in
SMOKE INJURY
The gases escaping into the air as the result of the in- complete combustion of coal, or the smelting of sulphurous
and other ores, cause symptoms in trees which are re- cognized as signs of smoke injury. While the above
two sources of harmful gases are the most important economically, there are a number of other sources which are accountable for similar, if less harmful, diseases.
Sulphur dioxide (SOa) is perhaps the most common and the most injurious of the gases found in smoke. Hydro-
chloric acid, hydrofluoric acid, chlorine, as well as the
finely divided solids found in smoke, have been recorded
as harmful to forest trees. Previous work has shown,
however, that smoke dust plays but a minor part in
causing injury to forest trees. While gases from industrial plants diffused iu the air
axe the prime cause of the disease of conilers and hard- woods resulting in a wine red to reddish brown disclora-
tion of the foliage, the part played by the relative hnmid-
ity, sunlight, and air currents is so important that I have included this disease in my discussion. Smoke injury
takes place only under specific conditions; i. e., when the
relative humidity is fairly high, when sunlight activates
the foliage, and when air currents move the fumes to the susceptible trees rapidly enough to prevent too great
diffusion of the harmful gases. In this manner meteoro-
logical conditions play most vital parts in the injury and
death of forest trees by gases in the air. The effect
produced on the host by smelter fumes, for example, so
closely resembles the symptoms of several other diseases
of conifers, including the various types of winter injury, that great difficulty is experienced in diagnosing the true
cause of the damage when it occurs.
RAIN, HAIL, AND SNOW INJURY
These meteorological agencies cause injuries which are usually of the type of wounds in the tender bark tissues
or of direct breakage of tips or branches. These injuries
are important in that they frequently form the infection
courts for parasitic and heartrot fungi. The sleet storms
common in the Lake States and North Atlantic States
often residt in very serioiis damage to trees over large areas.
An estimate of the total weight of sleet borne by poles supporting telephone wires during R severe sleet storm in
THER REVIEW NOVEMBER, 1930
Wisconsin during the early part of March, 1922, gives
us some idea of the strain which forest and shade trees are under when severe snow and sleet storms visit a
region. Estimatin that each linear foot of wire sup- ported 4 pounds o f ice, the 32-wire line with a span of
120 feet between poles had to carry a weight of 15,360
pounds in the face of a terrific gale. Even under such conditions the failures in the line were frequently traced
to poles which had been weakened by decay a t the ground
line.
WINDFALL OR WINDTHROW
While not, a true agency of disease excepting cases where prevailing winds acting upon exposed trees, such
as in high elevations, cause a deformity of the branches
and crown, yet wind action is an important factor in causing considernble loss in timber stands. Trees
weakened by such factors as decay fungi, shallow root systems, moist, loose soils, sudden exposure by cuttings,
site, etc., nre very prone to be ove.rturned by the force of strong winds. Within recent years large areas of
timberland have suffered this type of injury. The
breakage of tree trunks and of branches often results from high-velocity winds.
Such blowdowns, as they are termed along the
Pac,ific coast, have occurred in recent years along the Olympic Peninsula, where large areas of mature timber
have been swept to the ground. The tangled condition resulting from windfall and the isolated areas in which
they frequently are found, makes it impossible to salvage the timber before deterioration of the sapwood takas
place. Within two to three years much of the sapwood and some of the heartwood is deteriorated through sap
stain and decay fungi.
ELECTRICAL OR LIGHTNING INJURY
Lightning, aside from the setting of forest iires, causes
considerable injury to trees in a forest. The breakage of
tree parts and the splitting and shattering of tree trunks are the more conspicuous signs of lightning inury. How-
to spray lightning, for example, is often hidden beneath the bark
and reveals itself only as lightning scars in the annual
rings. These false rings along with those produced by frost and other pathological agencies are a common source
of error in counting the annual rings of a tree in an
attempt to determine accurately it,s age or an historicnl date in the life history of the tree.
Lightning rings are common in certain species of trees
and in trees growing in lightning zones. Sitka spruce, prized for its strength properties and light weight in air-
plane construction, frequently shows these false rings
caused by lighhing. As defects in airplane wood or
woods requiring rigid strength specificat,ions, these hidden
injuries are of considerable. e.conomic. importance, sincc failure under stress is most likely to t,ake place along a
false ring.
Before closing it will be of interest to dwell for a moment on the topic of ring or annual growth measurements in trees and their significance. Insufficient, precipitation
and the consequent lowering of the available water level
in the soil is responsible for more injury to forest trees than most of us appreciate. Drought injury not only causes reduced growth and reduced vigor in trees, but it
also predisposes the tree to attack by or anisms which
represents an appreciable loss and this brings before us
the interesting relationship between annual growth measurements mid periodic changes in annual precipita-
ever, the injury due to minor lightning bots, 1
hasten its death. The reduct,ion in annua k growth alone
NOVEMBER, 1930 MONTHLY WEATHER REVIEW 459
tion.
growt,h activity caused by a large number of fac,tors of which the annual supply of moisture is but, one. Any- thing, froni inseck attnc.ks, fire injuries, crowding of indi- vidual trees, sun sc.orch, to a variety of fungous and para-
sit,ic plant pest,s, mag leave their record in de,crerrsed
width of annual rings. The gre.at problem is to eliminate
all fac,t.ors but one in each study. It is also a well-known fact that the width of the same annual rings varies con-
siderably in different parts of t'he trunk. This makes it HARTIG, B. necessary to de.pend upon borings in various parts of the 1894. Diseases of trees. Pp. 282-294. The Macmillaii Co. t'runk from base to top. The frequent occurrence of false 2. NEQER, F. W.
rings, double rings, and the absence of certain rings all 1919. Die kraiikheiten unserer waldbaume (und wichtigsten
contribute, to the difficulty experienced in reading accu- 3. gartengeholae), c. p. viii, p. 286, 22-25. Stuttgart.
rately t,he past history of the t,re,e from the face of the 1912. Notes on winter-killing of forest trees. Forest Club
stump. (Nehr.) Annual, 4: 39-50.
I point out these facts to emphasize the large number 1918. Stem lesions caused hy excessive heat. Jour. Ag.
of variables involved and the need of accuniula.ting a 4. HEDacocK, Res. 14: G. 602. G. grent number of data on such growth c,orrelation studies 1912. Winter-killiug a i d smelter iiijiiry in the forests of
before conclusions may be hazarded. Montnua. Torreya, 12: 25-30.
-4n interesting piece of work of this nature has been 5. ~IUBERT, E. E. 1918. -2 report on the red belt injury of forest trees. done in our Idaho forests by Marshall (9), who found by
measuring the ring growth of western white pine trees 6. sTONE, G. E.
t,hat the climate of northern Idaho has exhibited distinc.t 1916. Shade trees, characteristics, adaptations, diseases,
wet. and dry periods, varying in length from 20 to 40 or more Mass. Ag. Exp. Sta. Bul. 170: 199-212.
pears. The wet periods he found to be from 1706-1745, 7- c. 1895. The influence of cold on plants--n r6sum6. Exp. 1785-1825, and froin 1846-1885. The dry periods were
sandwiched in between the wet periods and were from 1746-1785, 1826-1845, and from 1886-1925. 1926. Manual of plant ditieases. Pp. 136-138, 173-176.
These brief accounts represent but a few of the most
important tree diseases which may be placed a t the door 1927. Influence of precipitation cycles on forestry. Jour.
of the weat.her man. There are a number of minor dis-
-4 tree reflect.s in its annual rings any reduction in 5 turbances of the functions and damages to parts of trees
which have not been touc,hed upon. Enough has been presented to indicate the important rBle that meteoro-
logical conditions play in cmsi!ig economic losses in our timber stands. Windthrow, winte,r injury, and drought injury are done responsible for a very formidable loss
over a period of years.
LITERATURE CITED
Mont. - State Forester, Bien. Report, 5: 33-38.
and care.
Sta. Record, 6: 777-781.
.McGraa-Hill Book Co.
For. 25: 416-429.
8. HEALD, F. D.
9. hlarsha,l, R ,
THE RAINFALL OF SALVADOR1
By ADELBERT K. BOTTS
[Clark University, Worcester, Mas., Decsmber, 19301
The rainfall of Salvador is an esce.llent esaniple of Salvador, 2,076 feet above the sea, has one cont8inuous
west coast trade wind precipitation on the nort,hern wet season lasting froni April to Noveinher. It seem
margin of the equatorial rainfall belt. The awrage reasonable to assume that e.levation is t.he controlling aimual rainfall of the country is 75 inches, nn rt.inount factor in this situation, since a study of data for other
which is usually considered very bountiful. However, stations verifies the assumption and since t,he differences the distribution, both seasonal and areal, tends to restrict in latitude between the various stations is so slight as
the benefits to certain rather definite periods and places. to be negligible. Salvador is located on the western side of the Central Another modification resulting from increased eleva- American Cordilleras between the latitudes 13' and 14' tion is decreased variability in amount of rainfall re-
30' N. The central part of the country is occupied by a ceived from year to year. This fact is made evident by
belt of volcanoes, the highest one less than 8,000 feet a comparison of the differences in the absolute extremes
high, and most of the peaks less than 5,000 feet high. of rainfall by months for the various stations. On the
The ridge is high enough, however, to affect the distri- Cutuco chart the vertical lines between extremes are
bution of the rainfall. (Fig. 1.) The rainfall is con- very long. The length of corresponding lines for stations siderably heavier on the side exposed to the ocean than at higher elevations is generally sh9rte.r. A short line
it is in regions farther from and protected from the for any inonth indicates a slight vanabdity in the rain-
ocean. It is generally true that the amount of rainfall fall for that month, which amounts in fact to greater
varies directly with the altitude of the land. uniformity from year to year. San Salvador, the station
A comparison of the average annual rainfall conditions at the highest elevation, has, generally, the least monthly
of four representative stations shows further consistent variability in rainfall from year to year. That seems to
modification with elevation. (Fig. 3.) Cutuco has two indicate that rainfall over a period of years is somewhat
periods of ma-ximum rainfall, one occurring in June and more uniform at high than at low elevations.
the other in September. They are separated by a period Rather important in the seasonal distribution of rain- of distinctly diminished rainfall in July. For each of fall is the fact that a low total for a year does not imply a
the remahung three stations the sharp distinction be- consistently dry year, nor a high total a consistently wet
tween wet and dry periods during the summer months is year. For Cutuco, the year wit>h the least total ramfall progressively modified with increasing altitude. San (dotted line) shows rainfall niuch above the average for
the first part of the rainy period, with June for that year was presented to the Association of .h,merican Oeogrqpbera, in their twcnty-soven% annual meeting heid at Clark Uuiversity Worcester Mass. DW. 2v t'he wettest! June on IY3md. In that case the second Lo 31 1930. Acknowledgment for the data upon which tbis btudy is bn& mud bo mnde to d r . Fred Lavls, resident of Internationd Krbiiaays of Ckntral Amenca, who srnt lbe
materid to Clark Sniversity. ye was made RISO or hIr. W. W. Reed's article. Cli- t,ot,al while the first half of the summer was wetter than
usual. msblogIsal Data for Central America, in the bhNTE1.Y WEATHER HEVIEW, vol. 51,
p. l33.
(Fig. 2.)
I This stud
part of the rainy period was the one which cut down the