Rit (Vísindafélag Íslendinga) - 01.06.1975, Blaðsíða 16

by Bjöm Jóhannesson the PH is usually between 5 and 6, higher
in the North of Iceland than in the South. Thus the PH proved to
be 5.4 in mýri tracts in the South whereas it was 5.9 in the North.
It is therefore obvious that Icelandic mýri areas are less acid than
such areas in neighbouring countries. It should also be noted that
PH is often higher in the top layer of the soil, 10—15 cm., than in
the next layer below, and here the acid increasing effect of wind-
transported mineral dust is clearly evident (Jóhannesson, l.c., p. 54).
The constant transferral of mineral matter both by adfluvial
water and loess has probably contributed to the retention of pro-
ductivity of the mýri tracts for centuries on and without any efforts
having been made for improvement or cultivation.
Mound Patterns
The greater part of Icelandic mýri tracts is patterned, and the
mounds vary. The wettest mýri tracts, flói (level mire) and flæði-
mýri (alluvial mire) are almost always level. Upwards from the
flat plains there sometimes occur low ridges or hróf, which rise
slightly above the surrounding mire and coinciding with a sinking
of the ground water level. These ridges are almost without excep-
tion pattemed. Medium wet mýri tracts on lowland are almost al-
ways pattemed. Occasionally the mounds are low and level, at
which point the distinction between moimds and hollows becomes
blrnred. More often than not, however, the mounds are sharply
distinguished from the hollows although the mounds are never
very pronounced in normal mýri tracts. Much has been written
about the formation of mounds, which I have no reason to elaborate
here. It seems that mounds in general accompany a certain climate,
but I consider that the main reason for mound formation may
doubtless be traced to frost effect and solifluction. I simply want
to call attention to a few points, which all contribute to mound
formation.
1. Moisture content of the mire. It has already been mentioned that
the wettest mýri tracts are always level in the main. If we examine
a tract of mýri proceeding from its extreme border toward the center,
it is clear that closest to the border, where conditions are at their
16