Flóra: tímarit um íslenzka grasafræði - 01.06.1968, Side 49

In the lowland heath the number of species and the heterogenity
per 10 square meters, increases in proportion with the microrelief, from
very homogeneous flat heath to the most heterogeneous hummock
heath. In tlie latter one can find one hummock dominated by Empe-
trum, the next by Betula nana, the next by Salix phylicifolia, etc. There
is some heterogenity in the grooves too, which may be completely cove-
red by Loiseleuria procumbens in one place and by cryptogams like
Drepanocladus uncinatus, Hylocomium splendens, Rhacomitrium ca-
necens ericetorum, Ptilidium ciliare or Cetraria islandica in other
places. Only in Ljósavatn valley I saw a regular pattern with Arctosta-
phylos uva-ursi on the top of each hummock and Betula nana on the
sides, partly overgrowing the depressions.
An important part of the Icelandic heatli are the Vaccinium com-
munities: V. uliginosum and V. myrtillus, in places — most slopes stee-
per than 20° (fig. 1) — where the snow stays longer than elsewhere in
the vicinity. (Steindór Steindórsson.) Often I found at the border of
such a snow patch a small strip with Calluna vulgaris on a less steep
surface. Heather seldom dominates in the lowland heath of Suður-Þing-
eyjarsýsla (fig. 2), I think because the peaty soil is rather thick. In places
where the base rock is quite close to the surface, as, e.g., is the case in
extensive areas in the Faroes, one can find a heath dominated by Col-
luna. The sarne I noticed on the mountain slopes of the fjords district
in the East of Iceland. (fig. 3)
Crossing the heath in Suður-Þingeyjarsýsla I came to the neighbour-
hood of the hot spring area of Hveravellir—Reykjahverfi. The hot
spring next to the farm Bláhvammur yields a rather large quantity of
hot water, which largely runs down freely in three streamlets to the
Reykjakvisl creek. Only a small percentage is economically used for
heating purposes of the farm and a little greenhouse. I charted some
J
Fig. 2. Section of heath vegetation near Goðafoss. Note the special place of Juni-
perus nana. I ^ The flat patch at A. is dominaled by Calluna vulgaris, Peltigera
spec. and Ptilidium ciliare.
TÍMARIT UM ÍSLENZKA GRASAFRÆÐI - FlÓra 47