The Coconino sun., 1927-04-15
Sometimes Much Warmer
On Top of Peaks at Night
Than It Is in Flagstaff

G. A. Pearson, director Southwest
Forest Experiment station, near
Flagstaff, has just completed and sent
to Washington a book on forest types
and climate based on his findings as
silvirculturist during a ten-year
period just ended. Mr.. Pearson's long
study of the subject qualities him as
an authority. He spoke this week at
Santa Fe on this subject.
Following is a brief outline of his
findings and his methods of gathering
data:
Forest Types and Climate in Ari-
zona and New Mexico is the title Of
the report, which is soon to be pub
lished.
1t is matter of common knowledge
that as one ascends a mountain slope
the climate changes. In high mount
aims several climatic belts of zones
are encountered, each characterized
by distinctive kinds of vegetation.
The San Francisco mountains are
especially noted for their well defined
climatic zones. In timbered regions,
the various zones are readily recog-
nized by the trees which grow in
them, and for this reason foresters
call the zones forest types. In the
southwest, little natural tree growth
of any consequence occurs below
attitudes of 5000 feet, except along
water courses The lowest tree belt
is made up of pinons and jumpers,
or sometimes evergreen oaks. Above
this come the yellow pine forests such
as are found around Flagstaff; still
higher up in the mountain sides are
the fir forests, and finally the spruce
forests which occur only on relatively
high mountains.
Until recently, little has been
known about the climate in the high
mountains of the southwest, beyond
the general observation that it grows
colder and there is more rain as we
go up. In order to obtain more
definite information on this subject,
the experiment station in 1917 estab-
lished a series of weather stations in
the San Francisco mountains, begin
ming in the cedars at about $500 feet,
, and extending up the mountain at
intervals of from 1000 to 1900 feet to
timber line at II, 800 feet. BY means
of self-recording instruments, it was
possible to obtain continuous records
by visiting each station once week.
During the winter it was sometimes
impossible to reach timberline, but
the spruce station at 10000 feet was
visited regularly. In addition to
measurements of temperature and
precipitation, studies were made of
soil temperature, soil moisture and
vegetation. In connection with the
latter, pine, fir and spruce were all
planted in the different climatic zones
of forest types in order to see how a
tree behaves when taken out OF its
natural environment.
From the desert of southern Ari-
zona the timberline on the San Fran
cisco peaks, we have a range of
climatic conditions seldom encount-
cred within an equal horizontal
distance. Here, in an airline distance
of little more than hundred miles,
the change in temperature is as great
as that experienced In going from the
Gulf of Mexico to northern Canada.
At Phoenix, the mean annual tenn
perature is 695 degrees and the mean
annual precipitation is 7.53 inches.
Some so miles north in the pinon-juni-
per type (cedars) at an altitude OF
5000 feet, the temperature is about
SO degrees and the precipitation
about 16 inches. A rise of 1000 feet
takes one into the yellow pine type.
Here the temperature has fallen to
around 46 degrees and the precipltat-
ion has climbed to between 20 and "a
inches. At 5000 feet the yellow pine
has been replaced by frs, of which
Douglas fir is most prominent. The
temperature is in the neighborhood OF
al degrees and the precipitation close
to 80 inches. Ascending the slope
of the San Francisco mountains to
10.5OO feet puts us in the heart of the
dense spruce forest. Snow may be
found here up to July /, or even later.
The temperature has declined another
5 or 6 degrees and the precipitation
has increased to about 81 inches.
Another thousand feet takes us up to
timber line. All trees have disap-
reared except the spruce, and it has
become scraggly bush or is flat
tened out against the rocks like a
vine. Records show that the temper
ature is only degree or two lower
here than in the typical spruce forest,
but this along with shorter growing
season evidently is enough to pro-
hibit normal tree growth.
On the average, a rise OF iUOU Ieet
in altitude lowers the mean temper
ature by little less than degrees,
but the change iS not uniform. Inc
davs are invariably much cooler IN the
high attitudes, but this is not always
true Of the nights Many a person
who gazed at the sncW-ciad peaks on
a moonlight night speculating as to
the number of degrees below zero
would be surprised to learn that IT
was 5 or 10 degrees warmer on the
peaks than in Flagstaff. But on q
warm day In June when the mercury
passes the 90 mark in Flagstaff it
barely reaches So degrees at timber
line.
While temperature decreases with
a rise in altitude there is an equally
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