Rit (Vísindafélag Íslendinga) - 01.06.1975, Page 30

depending mostly on the different moisture content. Although E.
angustifolium is a hygrophilous plant it does not tolerate too much
water. If a dam develops in the flói, so that vegetation is suhmerged
for a longer or shorter period of time, the plant disappears alto-
gether e.g. in those places where ridges have formed and it is then
most often replaced by Carex nigra. The same has happened, where
dam irrigation projects were built in the Eriophorum flói, e.g. in
the Flói Irrigation Project. The surface of the Eriophorum flói is
mostly level, although its drier sections may be patterned by small
mounds, since they often come quite close to the mýri. However,
the water content of the Eriophorum flói is often highly variable.
In the wettest section, where E. angustifolium is pin-est, water
always reaches the surface level making this part of the flói
difficult to traverse on account of rot in the grass roots, although
the depth of the Eriophorum root is considerable. In other places it
dries out somewhat in summer, but the ground water always re-
mains at a high level, and during periods of rain water sparkles
everywhere amid the blades of grass.
Peat formation generally occurs everywhere and it is even abxm-
dant in the lowland but almost non-existent in the highland as
stated earlier.
The Eriophorum flói would appear to be rather unstable with
respect to vegetation, if the soil water is subject to change. It has
already been mentioned, how it can be transformed into a Carex
flói, if dams develop. Around ponds and pools rot patches often
occur in the grass roots, if the land absorbs some water e.g. after
two or more rainy summers in succession. By the same token E.
angustifolium quickly disappears, if the flói dries up to any extent,
in which instance it can be changed in incredibly short time into
meadow, where Agrostis canina is dominant. I have studied this
vegetation change in several areas in the proximity of drainage
ditches, which have been dug through the flói. E. angustifolium is
also vulnerable to haymaking and even grazing where it is inten-
sive. Where an E. flói has been mown annually for any length of
time, the growth of E. angustifolium diminishes and various spe-
cies come to the fore, which otherwise do not belong to that associa-
tion. This was very clear in Flói (Std. 1943 p. 31). Intensive grazing
can exert this same influence but on a smaller scale.
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