The Botany of Iceland - 01.12.1942, Blaðsíða 64

62
JOHS. GRONTVED
or valllendi (cp. T.T., 1914, p. 337). The subsoil consists mainly of
coarse sand and gravel, deposited by streams from melting snow. The
surface soil is a thin layer of humus. As already mentioned, the vegeta-
tion chiefly consists of grasses. This type of vegetation is here placed
under the designation “Grass Heath”.
The following list is taken from Molholm Hansen (1930, p. 52,
table 12 A) and gives the typical species from Deschampsia caespitosa•
valllendi in Lyngdalur, S. Iceland (D. 1) :
Agrostis tenuis
Festuca rubra
Deschamþsia caespitosa
„ flexuosa
Carex rigida
Viola palustris
Galium boreale
Equisetum pratense
Agrostis canina
Polygonum viviparum
Galium verum
In some places, however, Salix lanata and S. phylicijolia dominate
physiognomically, especially on freshly formed soil. Other chamaephytes,
such as Vaccinium uliginosum, Salix herbacea, S. glauca and Empetrum
nigrum occur more sparingly. Of other plants the grasses predominate;
otherwise, the same species are met with in the Sa/ix-valllendi as were
mentioned above in the Deschampsia caespitosa valllendi (cp. M.H.,
loc. cit.).
b. The Ling-heath (The Dwarf scrub vegeta-
tion). The heath formation in Iceland covers the lower part of the
mountain-slopes, extending as far upward as about 300—400 metres
above sea-level. Above this level it is replaced by the open fell field
vegetation (H.J., 1900, p. 69). At a lower level, below the mountain
slopes and in the lowland valleys, the heather mó is met with.
The species characteristic of the heath vegetation are the following
undershrubs:
Empetrum nigrum coll. Arctostaphylos Uva-ursi
Vaccinium uliginosum Calluna vulgaris
„ Myrtillus
These are the principal species, and each of them may be dominant
in patches, which naturally gives to the heath a very variegated ap-
pearance. A single species may in places predominate over a larger area,
thus we may speak of an Empetrum heath, an Arctostaphylos heath, a
Vaccinium heath, etc.—Pure Calluna heath is rarely met with.
Two other dwarf shrubs occur, namely Loiseleuria procumbens and
Cassiope hypnoides; usuallv these two species grow in patches, but