The Botany of Iceland - 01.12.1945, Blaðsíða 94

436
STEINDÓR STEINDÓRSSON
I shall briefly mention here what earlier authors say about this
formation. Stefánsson (1895, p. 196 ff.) describes the two closely
allied formations Empetrum and Betula nana mó, and in addition the
“mosathemba”, i. e. the Grimmia heath. J ó n s s o n does not mention
the actual dwarf shrub heath, either; the willow scrub described by
him is rather the Salix scrub found along rivers and brooks, and, as
pointed out above, the dwarf willow vegetation is largely a snow-patch
vegetation. This is a natural consequence of the fact that these two
authors never made the vegetation of the interior of the country the
subject of research. The first author to mention the actual dwarf shrub
heath isThoroddsen (1914, p. 315), who says: “Above the up-
per limit of the birch region an osier or a willow region may
be said to occur—in the centre of the country at an altitude of 500-800
metres, in other places somewhat lower—where willows are dominant
among the woody plants, although they have their greatest distribu-
tion at a far lower level, in the birch region itself. At this altitude they
do not form any coppice proper, but occur as flat expanses of low
prostrate shrubs. Above the birch region it is especially Salix herbacea,
S. lanata and S. glauca which are the dominants; Salix phylicifolia
retires, although low specimens of the latter are now and then met with
even at this altitude. Salix lan-ata, and to some extent S. glauca, occupy
large areas of the Iower parts of the plateau.” The same author goes
on to say (1. c. p. 340) : “As stated above, Salix lanata and S. glauca
are distributed over extensive sandy areas, and occur there, together
with some other plants, as dominants; in other places they occur on
dry, flat, clayey tracts, as scattered shrubs of low growth (20-60 cm.)
with an undergrowth of heather, Elyna Bellardi, various species of
grasses, etc.”
It is evident from this description that it is the dwarf shrub heath in
entirely the same extent as assumed by me which Thoroddsen men-
tions here. I should think, however, that his estimate of its vertical dis-
tribution (500-800 m) is too high. The lower limit, according to my
experience, is very nearly correct, whereas a closed Salix heath will
hardly be found at greater altitudes than 650-700 m. The Salix vegeta-
tion found at higher levels is a snow-patch vegetation. M 01 h o 1 m
Hansen describes a formation on Lyngdalsheiði (I. c. p. 53) at an
altitude of c. 200 m, which he refers to the valllendi vegetation (grassy
field). As far as I can see from his description, it is a shrub heath with
dominant Salix lanata. Noteworthy in this connection is M 0 1 h o 1 m
Hansen’s observation that this Salix lanata formation is principally