The Botany of Iceland - 01.12.1930, Page 75

STUDIES ON THE VEGETATION OF ICELAND
65
number of species and density are comparatively high, on an average
c. 40 species in 25 sq. m. with a density of c. 14. The southern
species play a much greater part than the arctic species; of the
life forms 14 predominate wilh an average percentage amount of
more tlian 50. Ch attain their minimum here; both above and
below tliey constitute a larger percentage amount of the vegetation
than here. The G percentage is somewhat higher tlian in the nio.
With regard to the (loristic composition, we find not only a
number of species from the mo, such as Empetrum nigrum, Vac-
cinium uliginosum, Salix herbacea, Polggonum viviparum, Thalictrum
alpinum, Agrostis canina, Festuca rubra, F. ovina, and Carex rigida,
but also a number of species which must be said to he peculiar
to the jaöar. Of these Deschampsia cœspitosa, the typical dominant
for the jaðar, must especially be noted, even though its F.-percenlage
is not always very high. Further Agrostis tenuis, Carex sparsi/lora,
C. capitata, Taraxacum offtcinale, Cardamine pratensis, and Viola
patustris, as also the Salix species, S. phylicifolia and S. lanala. Most
oí these speeies attain their maximum development liere. Of plants
peculiar to the mýri Carex Goodenoughii is the only one which
plavs any great part in the jaðar vegetation.
The Salix Mýri. Table 15 A—B, 4—6.
Similarly to the jaðar this formation has a large average
number of species and high average density, though not as high
as in the jaðar. While grasses were dominant in the jaðar here
‘t is the Cyperaceae, and the result is a great decrease in the H
percentage and a corresponding increase of the G percentage in the
biological spectrum. HH are graduallv gaining ground and are
represented by c. 6—8 p. c. in the spectrum. The Ch percentage is
soniewhat higher than in the jaðar. The jiroportion ol A and F
species is practically the same for this and the above-mentioned
lormation, hut there is a displacement within the suhgroups. Ihe
i- 2 percentage is comjiaratively high in the former, considerahly
lower in the latter formation.
Floristically the Salix mýri dilTers from the jaðar in that the
grasses play a very slight part, while the Salix species are the same.
Crom the Betula nana mýri it is distinct by the absence of the
characteristic species of tliat formalion, Betula nana, but it has llic
same cyperaceous llora. The dominant species are Garex Goode-
aoughii, Friophornm polyslachyum and the Saiix spp. especially
Hie Rotnny of lcelnml. Vol. III. 5