Full resolution (JPEG) - On this page / på denna sida - Sidor ...
<< prev. page << föreg. sida << >> nästa sida >> next page >>
Below is the raw OCR text
from the above scanned image.
Do you see an error? Proofread the page now!
Här nedan syns maskintolkade texten från faksimilbilden ovan.
Ser du något fel? Korrekturläs sidan nu!
This page has never been proofread. / Denna sida har aldrig korrekturlästs.
12
average of 10 estimations I obtained 0.s;4 mg., which is 41 % above
the normal. Since nearly all the values were taken in the day-time
under full sun, they represent amounts which really stand at the
disposal of the assimilaling vegetation.
The great variations are naturally associated with air-currents.
The estimations were carried out in the day-time with a fresh
breeze blowing over the tree-tops. On the ground only light puffs
were observed. The minimum value, 0.62 mg., was obtained with
obviously moving air, the maximum value, 1.25 mg., when the air:
was almost still. The estimation of Aug. 31, from 9.45 a. m. to
12 noon, when the value 0.71 mg. was obtained 2 metres above
the ground, shows that the higher CO, percentage reaches a little
way up from the surface of the earth.
In the literature there are very few statements as to the CO, per-
centage of the air in the forest. The most detailed investigation
seems to have been carried out by EBERMAYER (1885). From 84
estimations on the air of Bavarian forests he obtained the average
value of 0.0329 volumes per cent. Some of his values however are
almost twice as great. In thick beech-woods the maximum values
of 0.05149 and 0.0535 were found. The lowest values, 0,0:09 4 at a
minimum, were obtained in pinewoods, with a layer of moss cover-
ing the ground. EBERMAYER’s values therefore agree well with my
own experience. Since he sucked in the air from a height of 13
—2 m., the figures indicate that the air at the level of the under-
growth must have been considerably above the normal.
In tropical rainy forests still higher values than the above-men-
tioned might be expected. I have been able to find only two
estimations in the literature, viz. those by Mc LEAN (1919, p. 157),
carried out in the tropical forest near hio de Janeiro. Using
PETTENKOrER’s method he found 0.::» and 0.31% CO,, more than
10 times the normal therefore.
How matters are in regard to the CO, percentage higher up in
the wood, on a level with the tree-tops, has not yel been investi-
gated. I have only made a couple of estimations of air from an
oak-tree in Ulagap Bog. In the upper part of the head of the tree,
11.5 m. above the ground, the value 0.17 mg. per litre was obtained.
The same CO, percentage was found in the air around the lower
side of the tree-top, 525 m. above the ground. A simultaneous
estimation from a Siellaria nemorum-association a little distance
away gave 0.69 mg. per litre. On the occasion in question (July
<< prev. page << föreg. sida << >> nästa sida >> next page >>
