The daily morning journal and courier. [volume] (New Haven, Conn.) 1894-1907, 1901-08-10
ARCTIC VEGETATION.
Light Compensates for Inadequate
Warmth

|
Warmth
Professor J. Wiesner, of Vienna Tn
iversity, who for some years has beer
engaged in researches on the require
ments of plants in the matter of light
| has come to the following conclusions
with regard to the plants of the arctic
regions. The demonstration previously
put forward by him with regard tc
| the increase of latitude the light re-
| quirement of plants also rises, has beer
| shown, by observations made in Nor
! way and at Advent Bay, Spitzenbergen
| 1912 north latitude, to apply equally to
| sub-arctic and arctic regions. The rea-
sons for this marked need of light are
! the low temperatures which prevail at
the vegetative period, the want Of heat
being made up for by excess of light,
the amount of which must therefore in
crease with the decrease of tempera-
! ture. 1t thus comes about that a limit
Is set to the migration toward the Pole
Of bush and tree vegetation less by the
cold of winter than by the constantly
increasing need OF light, which can, of
course be less and less satisfied. AS a
rule the plants of the far north can
stand but small diminution of their
quantum Of light, such as is caused by
the interruption of the suns rave
through the configuration of the coun-
try.
Dr. Peucker's researches on noun
tain shadow have shown how the
amount of light required can be laid
down with precision In each particular
case. The intensity of the~ direct SUM-
light to which arctic plants are ex-
posed is very slight for it only becomes
perceptible when the sun reaches an
altitude Of fifteen degrees above the
horizon, whereas in the most favora BILE
case, on June 81, the sun only attains,
at Advent Bay, an altitude Of thirty to
thirty-five degrees. Direct sunlight
here at best reaches the strength of the
light radiated from the whole expanse
of the sky, the so-called "diffused
light" so that the whole illumination
availa BILE for polar plants is at most
double the amount of the diffused light.
The high Alpine plants of mean lati-
tudes, on the contrary, enjoy an
amount of illumination which may be
estimated at a maximum of at least
four times that due to the diffused
light the sun reaching a midday alti-
tude in summer of sixty nine degrees.
These differences result, as BONNER
has shown, in considerable varia tons
in the organs Of plants of like species,
which occur both in high Alpine and
high Arctic regions. In middle lati-
tudes the effect of aspect on vegeta-
ton is very striking, the northern as
pect on vegetation is very striking, the
northern slopes of mountains being Of
ten bare of plants. But in view of the
much nearer approach to a complete
circuit round the horizon made By the
sun in arctic ATTITUDES it is easily seen
that this influence is less felt there
than anywhere.
OF much interest, lastly, is the de-
morstration of the influence exercised
by differential lighting on the form of
trees the low angle at which light is
received especially favoring the pyra-
this is by no means detrimental under
the more nearly vertical lighting of low
ATTITUDES. The expresses of the south
are. in fact, protected by their form
from the injurious effects of a vertical
sun while the same form enables the
and Sweden to make the most of the
horizontal rays of the northern sum-
British Geographical Journal.