The Salt Lake herald. [volume] (Salt Lake City [Utah]) 1870-1909, 1908-10-11
BY r. Z.
Chief Inspector U. S. Forest Service.

SnieI inspector u b Forest Service.
] believe il was the day of my arrival
~ a Ioes.ns camp IN wyoming. my first
Trip INTO the irrigated region of the west
some eight years ago, that 1 was drawn
INTO an gum about the influence Of
nne forests on the climate and water sup
Ply, ana nave been arguing ever since.
me question appears to be equally as
STUBBORN of settlement as that of the
precise nature of electricity. and like them
IL VIII Tor a long time offer opportuni-
Hes Tor argument and conjecture. The
Factors which control the climate are too
indefinite, too difficult of measurement
and accurate observation, to permit Of
an explanation which will satisfy all the
natural laws involved. The more import
ant facts and principles have. of course.
neen observed, but the experts still find
II impossible TO lay down exact laws
or cause and effect or to forecast re-
suits in particular cases with any hope
of accuracy.
The question is. however. and particu-
iariy that part which relates to the eff
Iect on the water supply, one of vital
Importance to the American people and
ito the west especially, owing to the large
NUMBER OF uses 10 which water can be
put IN this region and the meagerness of
the supply as compared with that of the
eastern states.
The fact should not be lost sight of that
the scientists of the government prophesy
the exhaustion OF the coal supply in a
comparatively short time and that water
seems 10 afford the only feasible means
of providing power to replace steam. Al
ready the great railroad systems are pre-
karlns to e~lectrify their lines. and manu-
facturers all over the country are be-
coming anxious TO install electric plants
IN the place of steam.
OF Vital Importance.
Looking at the subject from every side
IL is plain nat the climate and the water
supply OF the country are of vital i'm
pcrtance 10 the nation and a collection
of the proven facts in regard TO the in
fluence of them on the forests will prob
aoly be OF considerable interest to the
people of Utah and adjoining states.
] cannot do better to start with than
quot from one of the highest authorities
on forestry. who p~refaces his discussion
OF forest influences with this statement:
The effects of these agencies nave been
observed and recorded from ancient times
down TO the present, and hundreds OF
pages could be filled with the record of
instances in which forest vegetation has
affected. or has been believed to have af-
Iected, the climate. the rainfall. the regu-
tation of moisture. the stability Of the
soil. the healthfulness of countries and
allied matters: if quantity of evidence
alone were wanted, the case might he CON
1t appears then, that from the earliest
times. there have been misconceptions i'm
regard to the actual effect of forests. and
a large portion of the supposed evidence
has been nothing. but opinions. and the
same can be said OF the present. The
proven facts are surprisingly few and
can all be set forth shortly under the
following headings:
Effect of Forests on Temperature.
Observations Of the temperature of the
arr IN forests covering a long term of
years shows that the whole effect of a
complete forest growth is a reduction in
the annual temperature of about l de-
gree.
BY seasons the effect is much more pro-
bounced the temperature in the forest he |
Ing about the same in the winter. l de-
gree cooler in the spring, , degrees in the
summer and l degree in the fall than in
the open. Again, the comparison of the
course OF the temperature during the day
IN the forest and in the open is a little
more striking. In the summer time at
night the air is > to 3 degrees warmer
IN the woods, IN winter only slightly
warmer. In the hottest part of the dav
IN summer the woods are as much as 7
degrees cooler, and in winter 2 degrees
cooler than in the open. / think this fact |
IT Is Just ABOUT the difference which can
be noticed in a change from the heat i'm
the business district of the CITY and the
cool shade OF the trees in the suburbs or
in Liberty park.
In short. the forests lower the tempera-
ture of the air during the dav and in
crease il during the night. and the diff
ference is most pronounced in the sum-
mer time In other words. the forests
tend to moderate the extremes of heat
The above figures apply only locally.
of course Attempts have been made 10
determine the effect of large areas of
forests. and while the indications are that
the moderating effect is considerable.
there are 50 many stronger influences
attitude. air currents, presence of large
sheets of water. swamDs. etc. that an ac- |
curate deduction cannot be made.
Temperature of the Soil.
Since the temperature of the soil must
follow that of the air, the same differ
ences between the temperature of the soil
IN forests and in the open. as were noted
IN the air, are found. The difference in
the winter : almost inappreciable. while |
In summer The soil in the forests is from
s to ! degrees colder than soil in the
open. Also the difference is much great
er in evergreen forests than in one COM
posed of trees which shed their leaves.
This effect of forests in lowering the tenn
perature of the soil is important. in as
much as II shortens the season of growth.
vegetation in forests starting later in the
spring ana stopping earlier in the fall
than in the open.
Effect on Air Moisture.
on the absolute humidity of the air.
or the weight of water in a given uuan-
uty of air. forests have only a very
slight, if any. effect.
Their effect on the relative humidity.
however. or the degree of saturation is
pronounced. since the air in the forests
IS cooler than in the open and can alb
sorb A smaller amount of moisture than
the warmer air outside the forests With
the same absolute humidity cold air will
be nearer the point Of saturation, or the
PUNT at WHICH, lHt moisture or the air will |
be condensed inJo the water. and this
fact may be of great Importance in the
effect of the forest on the rainfall of a
region.
\ long series of experiments proved that
the relative humidity of the soil in for
ests ranged from 3 TO 10 degrees higher
than in the OPEN. the difference being
greatest at high attitudes.
This last fact every one in the west
is aware of. for it is evidenced by the
ease with which clouds form on mountain
ranges As CDmnITRn with tho ruaTIa,-- 81
deserts.
The kind of trees which compose the
forests appears to have some effect on
the relative humidity. it being greater in
dense spruce forests than in forests of
hardwood or pine.
Influence of Forests on Rainfall.