The Botany of Iceland - 01.12.1930, Síða 173

STUDIES ON THE VEGETATION OE ICELAND
163
By the investigations described in the present treatise it has
been shown how, within 3 areas in normal Icelandic physical con-
ditions, favourable conditions for southern species are created, and
thus a vegetation, the luxuriance of which permits of grazing or
haymaking. These areas are either soils protected by water or by
snow, or moderately moist soils which combine the favourable
temperature conditions in winter of moist soils with the favourable
temperature conditions in summer of dry soils.
The value of these areas for farming is caused by the fact that
southern species and life-forms are larger and more vigorous, pro-
duce more matter than northern ones. Hence one of the chief
ainis in cultivating infertile areas should be to make such changes
111 the prevalent external factors that from being favourable to Ch
they become favourable to H or G, according as the soil to be cul-
tivated is comparatively dry or comparatively moist. The means
employed for this purpose liave been, partly a change in the con-
ditions of moisture, partly in the conditions of nutrition. The re-
sults have, however, been very varied. The experiments have been
most successful in the case of mýri, which it has been attempted
cultivate partly by irrigation, partly by draining. It is obvious
that irrigation must result in favourable conditions for southern
P'ants, since it increases the medium of protection against the winter
cold. If the water is drained ofl' in tlie summer, this will merely
he a further advantage, since a lot of heat which would otherwise
be latent in the water now becomes available for the plants. As a
matter of fact, the transformation of mýri into irrigated mýri plays
a prominent part in Icelandic farming.
The second way in which mýri may be transformed is by
draining. In that way moist soil is transformed into moderately
m°ist soil, mýri to tún. This change in moisture in connection
'vith tlie addition of manure will have the efffect of gradually re-
placing the sedge vegetation of the mýri, rich in G, by the grass
'egetation of the tún, rich in H — a vegetation identical with the
jaðar vegetation. Thus draining also produces a more southern
vegetation, and the causes have previously been mentioned.
In the cultivation of the mo it has especially been attempted
*() transfonn il into tún. By treating the soil and adding manure
lo it, it has been attempted to make the jaðar plants grow here,
ar*d with some success. Hitherto, however, the object has been to
transform a less soulliern to a more southern type of vegetation
n