New-York tribune., 1901-08-04
ARCTIC VEGETATION.
LIGHT coMPENsATF:s FOR INADEQUATE WARMTH
From The British Geographical Journal

LIGHT coMPENsATEs FOR INADEQUATE WARMTH,
From The British Geographical Journal
Professor j. Wiesner. of Vienna University
VINO Tor some years has been engaged in re
searches on the requirements of plants in the
matter of light has come the following con-
clusions with regard to the plants of the arctic
regions The demonstration previously put for
ward by him with regard to low and middle
ATTITUDES, that with the increase of latitude the
llSht require rement of plants also rises has been
SHOWN by observations made in Norway and at
ADVENT iiay. SpItzenherSen, IS:l2 north latitude,
TO apply equally TO Sub-arctic and arctic re-
Rlons The reasons for this marked need of
light are The low temperatures which prevail
at the Vegetattvc period, the want OF heat be
ing made W for by excess of light the amount
of which must therefore increase with the Ge-
crease OF temperatures. 1t thus comes about
that limit is set Ia the migration toward the
Pole of bush and tree vegetation less 10y the
cold of winter than 10y the CONSTANTS Increasing
less satisfied As rule, the plants Of the Far
North can stand nut u small diminution Of their
quantum OF hcht such as is caused hy the in
Perception of IN" suns rays through the con-
fSuratDn Of the country.
Dr. PcucEcr'S researches mountain shadow
have shown how the amount Of light required
can be laid down with precision in each par
ticular case. The intensity of the direct
liSht 10 which arctic plants are exposed is very
light for it only becomes perceItible when the
sun reaches an altitude Of II degrees above the
horizon. whereas in the most favorable case. on
June II the sun only attI:nS, at Advent Bay,
an altitude of 30 L. - degrees. Direct sun
light here al best reaches the strength of the
sky, the s"-called "iinused light" 81 that the
" hole Illumination available for polar plants
is AZ most double the amount of the difused
light. The high Alpine plants Of mean ATTITUDES.
on the contrary enjoy an amount of lumna
! ton which may be estimated at maximum
OF at least four times that due To the diffused
| light, the reaching a midday altitude in
, summer 0f 81 to - degrees. These differences
J result. BONNER has shown in considerable
variations in the organs of plants of like Spe
Cics. which occur both in high Alpine and high
Arctic regions. In middle ATTITUDES the effect
3 OF aspect vegetation is very striking, the
northern slopes Of mountains being often bare
/ OF plants But in view of the much arer APP
pruaCh 10 complete circuit round the horizon
made by the in arctic latitudes u is easily
seen that tins influence is less felt there than
anywhere.
OF much interest. lastly. is the demonstration
Of the influence exercised 10y diffcrentia lighting
on the form of trees, tn" low angle at which
! light is received especially ia vorinE the pvra-
midal shape in arctic ATTITUDES. though this is
by rScanS 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 Verti-
/ cal sun. while the same form enables the frs,
, pines and white poplars of Norway and Sweden
| to make the most Of the horizontal rays of the
/ Northern