The Botany of Iceland - 01.12.1945, Side 89

The Botany of Iceland - 01.12.1945, Side 89
THE VEGETATION OF CENTRAL ICELAND 431 vegetation period is reduced, so that it will be too short for them.” (translated from the Danish). Although my observations here are too few to warrant perfectly valid conclusions, I should think that up to an altitude of c. 650 m the snow-covering in the snow-patches will further the growth of the southern species, if we are not concerned with “extreme” snow-patches. Beyond this altitude the time which the snow-patches will afford the plants for their growth is too short for the southern species. In the life-form spectrum similar fluctuations will be seen as in the species group spectrum. Especially the Ch percentage is somewhat lower than the A percentage except in group I, where the Ch percentage is particularly high. The H percentage agrees fairly well with the flora spectrum, but decreases considerably with the altitude. The geophytes generally show much higher percentages in the snow-patch spectra than in the flora spectrum, from which we might perhaps conclude that the snow-patches afford comparatively favourable life conditions to this life-form. The Th percentage is altogether lower in the snow- patch spectra than in the flora spectra, but show no special tendency to change with the altitude. It is fairly evident that the hemicrypto- phytes decrease in the snow-patches with increasing altitude, and they are likewise as a rule reduced in the “extreme” snow-patches. M 01- holmHansen’s contention (1930, p. 154) that “... where the snow-covering is deepest, H play the most pro- minent par t”, accordingly only holds good until the snow-cover- ing attains a certain duration. If this limit is exceeded, the hemicrypto- phytes will be reduced, mostly for the benefit of the chamaephytes. Below I have divided the snow-patch associations according to the thickness of the snow-covering in the particular places into three groups. As no measurements are at hand, this estimate of the depth of the snow is, of course, based on a consideration of the terrain, but it is hardly far out. Group A: snow-covering scanty compared with other snow-patches, Ass. 1, 2, 3, 8. — B: snow-covering moderately thick compared with other snow- patches, Ass. 4, 5, 7. C: snow-covering thick compared with other snow-patches, Ass. 6, 9, 10, 11. Finally I mention the species occurring in the snow-patches in- vestigated by me. I have arranged these species into two groups, of which group I is divided into two subgroups.
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The Botany of Iceland

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