The Botany of Iceland - 01.12.1945, Page 156

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STEINDÖR STEINDÓRSSON
Table XXVII gives the results of a series of analyses made on the
north-facing side of the mountain Sáta. Here we obtain a somewhat
different picture from that gained on the south side of Loðmundur,
in spite of the small distance and though the rock is the same in both
mountains. The lowest-lying locality is here found at an altitude of
c. 600 m, and above this the analyses were made at intervals of c. 50 m.
Analysis 1 was made on a damp flat dominated by Calamagrostis; the
snow-covering lingers fairly long here, and the analysis was poor in
species.
In Sáta, which is exposed towards the north, the whole vegetation
is far more scattered and mosses are more conspicuous physiognomically
than on the south-facing side of Loðmundur. At an altitude of c. 700 m
the Grimmia heath replaces the brekkur formation, which, however,
is never pure, but is strongly marked by the moss heath, though Grim-
mia is less dominant than in the typical Grimmia heath and is mixed
with several species of mosses. Analysis 2 and 3 were made in this
mixed vegetation, 4 and 5 in the pure moss heath.
A comparison of these two altitudinal series shows that the analyses
from Sáta from 600-800 m correspond almost perfectly to those from
Loðmundur from 700-900 m altitude, i. e. analyses 4-7 in Table XXVI.
Notably the A percentage is almost the same, while the Ch percentage
is generally higher in Sáta than in Loðmundur. Since other conditions
than the exposure can be said to be the same in the two localities, it
is very tempting to ascribe the difference in the vegetation to the in-
fluence of the exposure. It causes the curves for the same Ch and A
percentages to lie c. 100 m higher in places with a southward than in
places with a northward exposure. This difference is even more distinct-
ly manifested in the physiognomy of the vegetation than it can be
expressed in tables.
As an account has now been given of the life-forms, it will be
natural to consider the vertical distribution of the individual species in
these two localities. I have divided the species occurring in the analyses
from Loðmundur into five groups according to their vertical distribu-
tion. Their occurrence in the analyses from Sáta is indicated in a special
column.
Group I. Species common in all the analyses, i. e. such as are apparent-
ly indifferent to the altitude.