Náttúrufræðingurinn - 1961, Blaðsíða 19

NÁTTÚRUFRÆÐINGURINN
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of Iceland (Tables 1—3) during the years 1924—1945. However, these quoted
results tnust be treated somewhat cautiously like many other earlier soil
temperature measurements, since prior to readings each thermometer had to be
withdrawn from its otherwise normal position. None the less, it seems possi-
Ule that the annual march of temperature for the 100 cm and 200 cm soil
depths at Reykjavík will resemble tliat shown in Fig. 1, although the tempera-
ture levels by tliemselves may be inaccurate.
As regards the data shown in Table 4 no information about instrumentation
has been discovered nor is the exact locality of measurements known.
The secoiul part of the paper deals with some of the authors own results,
but must all be regarded as preliminary. Table 5 sunnnarizes few observations
ntade during the sumrner 1957.
Table 6 shows preliminary results from a more systematic study initiated
by the author (cf. Helgason, B., 1961. „Some Observations on Soil Tempera-
tures in Iceland". Nature (Loiulon) 191: 939) in summer 1960, and
which it is hoped to continue over a period of several years. In this connection
observations regarding minimum temperatures at night and the occurrence
of night frosts were also made. These are summarized in Table 7. The incresased
outward-radiation at night from the exposed soil as compared with that under
permanent grass, — restdting from the free heat exchange between the ex-
posed soil and the air above, is clearly indicated by these data. It is further
shown by the occurrence of night frosts which were recorded above the grass
as follows: 1 in june, 1 in July and 2 in August but none above the exposed
soil. In September l'rost was recorded on 4 nights above the grass, while on
2 nights above the exposed soil.
The paper concludes witli a few remarks about tlie necessity of extending
the above observations into proper systematic study to be continued over a
period of years. Its usefulness, especially in relation to seeding and planting
in spring, occurrence of night frosts during the growing period, the effective
use of fertilizers and the penetration of frost during winter, is pointed out.