Fróðskaparrit - 01.01.1968, Síða 118

126
Gróðrarleivdir (sáð) av dvørgabjørk
washing a peat sample from Boðanes, Streymoy, a fruit of Be-
tula pubescens was found. At Gjógv, Eysturoy, a peat bog
covered with beach gravel contained a lot of birch wood with
its bark on it. However in this bog there was also driftwood
of Picea (or Larix), so probably tihe birohwood has been
washed up from che sea. These are the only two findings of
macroscopic birchremains in Faroese paatbogs. The fruit and
the wood must have been transported to the Faroes by flhe
wind and the sea respectively because under the microscope I
have found no evidence to support the view flhat birch has
been growing in the islands«.
My diagram from Hoydalar shows these percentages for
Betula: at flhe bottom 8%, rising to 50%, and again falling
to 8°/o in the uppermost samples.
By size statistical meflhods it is possible to distinguish B.
nana from tihe tree species. In four levels — A, B, C and D
— I have measured the size of the Betula pollengrains. Especi-
ally HF and acetolysis will influence the size of the pollen
grains strongly, but wihen all the material which shall be
compared is treated in che same way, che effect on the size
will be tihe same for all the pollengrains.
The result is seen in fig. 2 and must be irtterpreted in this
way.
A 8°/o Betula. Tree species — longdistance transport.
B 15% Betula. The rise is partly due to B. nana, while
still most of tihe Betula pollen is transported from tihe neigh-
bouring countries. Until more localitiies from the Faroes are
investigated it is not possible to decide whether an immi-
gration of B. nana comes from other countries or only from
other parts of the Faroes.
C 50% Betula. It is now B. nana pollen which is com-
pletely dominating. We still have tihe same amount of long-
distance transported treepollen, tihe percentages now being
suppressed by B. nana.
D 8,5%. The three species again dominate, but it seems
that there is still some B. nana left. We may assume that it