The Botany of Iceland - 01.12.1930, Síða 181
STUDIES ON THE VEGETATION OF ICELAND
171
Table 35. Average Maxima, Minima, and Amplitudes
of various Soils. After Homén. 1897, pp. 47—48. The investigations
cover the period 10—13 August 1893.
Granite Sandy heatli Bog
Max. Min. DifT. Max. Min. Diff. Max. Min. Diff.
Air temperature G° . . . 22.7 9.6 13.1 » » » » » »
Vegetable covering ... 32.5 12.6 19.9 37.7 6.4 31.3 32.8 2.2 30.7
0 cm 34.8 14.5 20.3 42.3 7.8 34.6 27.7 6.3 21.4
1 » 33.1 15.2 17.9 1 35.9 9.7 26.2 23.9 8.9 15.3
2 » 31.9 15.8 16.1 30.6 11.3 19.3 20.6 11.1 9.6
5 » 30.4 16.6 13.8 24.7 12 8 11.8 16.7 13.9 2.8
10 » 28.9 17.2 11.7 22.2 14.4 7.8 16.2 14 8 1.5
20 » 26.1 18.2 7.9 19.4 15.5 3.9 15.3 14.9 0.4
30 » 24.3 19.1 5.2 17-7 15.9 1.8 14.3 14.2 0 1
40 » 22.9 19.5 3.4 16.2 15.5 0.7 13.5 13.4 0.05
50 » 21.7 19.6 2.1 15.0 14.8 0.3 12.4 12.4 »
60 » 20.9 19.6 1.4 14.2 14 1 0.1 11.7 11.6 »
clothing of vegetation liave been made in Finland by Th. Homén
nnd described in a series of works (1894, 1896, and 1897). Tables
35, 36, and 37 give the chief data of these works. Table 35 com-
prises the daily heat maximum, heat minimum, and amplitude for
granite, sandy soil, and boggy soil, respectively a solid, a loose, and
a damp rock. The figures are the mean values of a series of in-
vestigations. Table 36 shows the daily amplitude for various kinds
of soil, sandy soil, clayey soil, and boggy soil with or without wood
or a covering of cultivated plants (cereals). Table 37 shows the
annual mean temperature, the annual variation in temperature, i. e.
the difference between the mean temperatures of the coldest and
vvarmest months and the mean temperature of each month at different
cíepths in soils with a different clotliing of vegetalion, thus at 0.5,
10, and 2.0 m for open grassfield, birchwood, and firwood.
A comparison between the temperature conditions of solid rock
and loose sandy soil shows a much greater current of lieat in the
solid than in the loose soil. Taking the average of 4 days, the
surface of a granite rock will be lieated to 34.8° by day. The heat
accumulated at the surface will comparatively rapidly spread down-
wards so as to make the temperature maximum at a depth of 60 cm
no less than 20.9; for sandy soil the same figures are respectively