Fróðskaparrit - 31.12.2000, Blaðsíða 42

46
A REVIEW OF PLANT COMMUNITIES OF THE FAROE ISLANDS
The Racomitrium lanuginosum heath is de-
scribed by Ostenfeld (1905-1908) as a veg-
etation type found on sloping terrain on rel-
atively dry soil protected from wind.
Racomitrium lanuginosum is widely dis-
tributed at all elevations, while R. cane-
scens is only found at altitudes above 300
m.a.s.l. (Jensen 1901). Bócher (1937) di-
vided Racomitrium vegetation into two
main types: Racomitrium lanuginosum rich
vegetation and Racomitrium canesces rich
vegetation. He found that the R. canescens
associations are typical snow-bed associa-
tions with Sibbaldia procumbens and
Veronica alpina. The Racomitrium cane-
scens association was dominated by Bistor-
ta vivipara, Agrostis canina, Sibbaldia pro-
cumbens, and Salix herbacea. Two snow-
bed associations were described: (1) the Al-
chemilla alpina — Sibbaldia association
with considerable amounts of Racomitrium
canescens', and (2) the Salix herbacea -
Carex bigelowii association, with consider-
able amounts of Bistorta vivipara, Agrostis
canina, Thalictrum alpinum, and Anthelia
nivalis. Hobbs and Averis (1991) described
one snow-bed association where snow was
found in late July. This association is sim-
ilar to the British Salix herbacea -
Racomitrium heterostichum association,
with Kiaria starkei, Salix herbacea, Anas-
trepta orcadencis, and Barbilophozia ly-
copodoides. These associations usually
make transitions to Nardus - Racomitrium
associations (Ostenfeld, 1905-1908),
which usually are found in snow-free areas
on the edge of snow-bed vegetation.
Bocher (1937) found one species-rich
Racomitrium lanuginosum heath at lower
altitudes (400-600 m.a.s.l.) where Festuca
vivipara was the dominating species, and
one species-poor Racomitrium lanugi-
nosum heath from higher altitudes (600-
882 m.a.s.l.) where Salix herbacea was the
dominating species. In the species-rich R.
lanuginosum heath, he defined two associ-
ations, one Festuca vivipara - Racomitrium
lanuginosum association and one Em-
petrum - Festuca vivipara - Vaccinium
myrtillus - Racomitrium lanuginosum as-
sociation. The first association had a con-
siderable amount of Thymus praecox, Al-
chemilla alpina, and Agrostis canina, while
the second had Galium saxatilis in addition
to the three mentioned from the first associ-
ation. In the species-poor R. lanuginosum
heath. Bðcher (1937) defined three associ-
ations, the first is a Salix herbacea -
Racomitrium lanuginosum association, the
second is a Bistorta vivipara - Racomitri-
um lanuginosum association, and a third is
a Carex bieglowii - Racomitrium lanugi-
nosum association. A Salix Herbacea - Bis-
torta vivipara association was described by
Hansen (1967). Hobbs and Averis (1991)
compared the Racomitrium heath with the
equivalent in Britain, the Carex bigelowii -
Racomitrium lanuginosum association Si-
lene acaulis sub-association. They found
that the Faroese type is more extensive and
descends to a lower altitude. On alpine
slopes, Bocher (1937) described a Nardus-
Hylocomium association with Agrostis can-
ina, A. cappilaris, and Festuca vivipara.
Dominating mosses in this association
were Rhytidiadelphus loreus and R. tri-
quetrus.