Rit (Vísindafélag Íslendinga) - 01.06.1975, Side 40

which are continuously flooded by water, but not deep enough for
a dam proper to form in the long run. The water is deep enough
to reduce the growth of E. angustifolium and C. rariflora, neither
of which tolerates substantial damming, although they are hygro-
philous. On the other hand species appear here which otherwise
do not actually belong in Eriophorum flói areas. Among these is
first and foremost Carex Lyngbyei and, to be sure, the hybrid
C. Lyngbyei x C. Bigelowii, which can also grow in various flói
areas. The topography and physiognomy of vegetation at the ob-
servation sites were determinative factors. I accordingly classified
these vegetative areas with the E. angustifolium — C. rariflora
sociation, although they differ somewhat. These observation sites
are also good examples of the change which takes place when the
water level in the flói alters. Analyses 13-16 are all from Gnúp-
verjaafréttur. Number 13 is from a hollow in a Palsamire (flá),
but the others are from the great flói tract Nauthagi, which is to
the south of Hofsjökull. With respect to its development the flói
there is akin to the Eyjabakka-area, i.e. the bottom layer is fluvio-
glacial and peat formation is probably non-existent on top of the
base layer. The fluctuation of the ground water is probably con-
siderably more pronounced than prevails as a rule in the flói. The
sociation there occurs in shallow depressions, but the intervening
undular formations are covered with Carex Lyngbyei — C. rariflora
— Salix glauca sociations (Tab. V 9—10). It is difficult to explain
how C. Lyngbyei can disappear altogether to be replaced by E.
angustifolium, but it should be noted that E. angustifolium is less
frequent here than normally applies in the Eriophorum flói. C.
rariflora is dominant everywhere in covering and in many places
much more abundant than E. angustifolium. Moss is considerable
and in some parts some Sphagnum, so that the surface becomes
pattemed with knobby mounds. Although the Eriophorum and
Carex Lyngbyei associations are intertwined in a mosaic of sorts,
the border between them is sharply drawn by extremely narrow
transitional belts. When the area is surveyed it changes colour
distinctively between the hght green C. Lyngbyei association and
the hazel E. angustifolium — C. rariflora association. As far as I
could determine the relationship of the sociations is as follows: The
entire area is dissected by shallow brooklets more or less filled with
40