The Botany of Iceland - 01.12.1930, Page 183
STUDIES ON THE VEGETATION OF ICELAND
173
of the three types of soil. Very striking is the daily variation in
temperature, this is not onljr rather small at the surface, but already
at very slight depths it is practically nil.
Table 36 shows the average daily variation in temperature for
sandy soil, clayey soil, and boggy soil, with or without a covering
of vegetation i. e. of cornfield or wood. These investigations show
the same conditions as table 35, viz. that sandy soil has a greater
daily variation of temperature than boggy soil at the same depth,
and that the daily variation in temperature penetrates to greater
depths in sandy than in boggy soil. If the soil is covered with
vegetation, i. e. wood or cornfields, the result will be in the flrst
place a decrease in the daily variation of temperature.
Table 37. Annual Variation of Temperature
in Soils witli different Vegetable Covering in Heináis, Finland.
After Th. Homén 1890, p. 147.
U « C3 'S February Marcli < May June July August September October November December Year DifTerence
Firwood 0.50 m 1.0° 1.2 1.0 1.1 4.1 10.4 12.6 12.8 10.7 6.5 3.7 2.1 5.7 11.8
1.00 > 2.3 1.8 1.4 1.3 2.9 7.5 10.0 11.0 10.0 7.3 4.7 3.1 5.3 9.7
2.00 » 3.6 2.9 2.4 2.2 2.6 4.7 7.0 8.5 87 7.7 5.8 4.3 5.0 6.5
BirchwoodO 50 m 1.0° 0.4 ci •I- 0.3 2.3 7.5 10.2 10.9 9.4 5.6 3.0 1.6 4.3 11.1
1.00 > 2.0 1.5 1.0 O.S 1.8 4.9 3.4 8.7 8.4 6.3 4.3 2.9 4.2 7.9
2.00 » 3.5 2.9 2.6 22 2.3 3.9 5.7 7.0 7.5 6.8 5.6 4.4 4.5 5.3
Grassfleld 0.50 m 1.1° 0.6 0.3 0.4 1.0 4.6 8.5 9.8 8.7 5.6 3.3 1.6 3.8 9.5
1.00 » 2.0 1.4 1.0 0.9 1.1 3.3 6.5 8.1 7.9 6.1 4.2 2.7 3.8 7.2
2.00 » 3.1 2.4 2-0 1.7 1.6 2.3 4.3 5.8 6.4 5.9 4.9 3.8 3.7 4.8
A similar series of investigations on annual variations in tempe-
rature and temperature conditions is only found respectively for
sunny open and wooded sandy soil, but unfortunately not for damp
soil, whether such as is constantly damp throughout the year, or
Slich as is damp in winter but dry in summer Table 37 (after
Homén 1896) shows the annual mean temperature at various depths
f°r respectively sunny open and wooded soil, the mean temperature
°l each month and the difference between the lowest and highest