The Botany of Iceland - 01.12.1930, Síða 171
STUDIES ON THE VEGETATION OE ICELAND
161
The knolly mo...... 6.8, 6.8, 6.4, 6.2 average 6.5
Jaðar.............. 6.2, 6.2, 6.1, 6.1 — 6.2
Mýri............... 6.3, 6.1, 6.0, 5.9, 5.9, 5.6 — 5.9
Geiri (Geranium belt) ... 6.5, 6 4 — 6.3
— (bottom veget.) .... 6.3, 6.1 —
Thus the Icelandic soils all seem to be slightly acid; no degrees
of acidity above the neutral point were measured, nor did any very
strongly acid soils occur. The highest value measured in pH was
6.9, the lowest4.8; according to C. Olsen, the corresponding values
íor Denmark are respectively 8.0 and 3.4. There is this connection
between the moisture of the soil and its degree of acidity tliat in-
creasing moisture produces increasing acidity, i. e. decrease in pH
value. In melar pH is about 6.7, in the mo 6.3—6.5, in jaðar 6.0—
6.2, and in mýri 5.2, 5.5, and 5.9. An increase in the depth of
snow-covering shows the same relations: in melar pH is 6.7, in mo
6-3—6.5, and in geiri 6.1—6.3.
The investigations described in the present treatise are not only
ot phytogeographical and botanical interest, but would also seem
to have some bearing on practical matters, partly in agricullural
research, and partly more directly in farming. Since, however,
these matters liave not been subjected to special investigation and
are outside the scope of the present treatise, I shall merely make
brief mention of a couple of questions connected herewith.
Under the treatment of the vegetation the appearance of the
surface in the individual types was described. A comparison be-
tween this and the species group spectra reveals the following facts.
Wh en the E percentage is high, i. e. when the vegetation
consists of southern species, the surface is always level,
without any formation of knolls, whether the high E per-
centage is caused by a deep layer of snow or by the soil being
covered with waler. If, reversely, the vegetation consists
niainly of arctic species, solifluction is always seen. If
the vegetation consists of an equal mixture of A and E
species knolls will always be met with.
This difference between the types of surface connected with
the diflerent types of vegetation must be assumed to be a result of
the same external factor that determines the differences in vege-
tation, in this case the cold. In geiri and flói (snow-patch and
The Botany of Iceland. Vol. III. U