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BIDRAG TILL SKÅNES FLORA 37. QUERCUS PKTRAEA
197
humus layer (A0) is a few or rarely up to 8 cm thick, whereas the
leached I ayer (Aj) usually amounts to 10—20 cm, sometimes, however,
to as much as 40 cm.
The rust-coloured horizon of deposition (B) occupies in the
moraines usually 30—50 cm, in the coarse material deposited in glacial
rivers it forms a much thicker layer: 50—100 cm, sometimes still more
(fig. 5).
Great soil samples have been taken for mechanical analysis in the
B or when possible in the C horizon. As the soils mainly contain a large
% of stones, pebbles and coarser fractions it has been necessary to take
verv great samples, usually between 15 and 20 kg. The larger stones
(>60 mm) were previously detached and have thus not been counted
in the analyses. After the samples had been dried in the sun Ihe first
sieving was made already in the field with a 20 mm sieve. Stones with
a diam. of 20—60 mm were then weighed. Further analyses were made
in the soil laboratory of the Botanical Institute, Lund. The results of
these investigations appear in table 1, where samples have been brought
together into two groups: nr. 1—26, 39, 40, which represent material
assorted by glacial rivers, and nr. 27 - 38, 41, 42, which belong lo gneiss
moraine.
In the first mentioned soils the finest fractions, »very fine sand»
and smaller particles, in most cases constitute a comparatively small
pari of Ihe whole, but these fractions have a greater significance in the
moraines.
In the profiles I have laken smaller soil samples in the different
horizons and subhorizons for the determination of soil reaction. The
samples from the uppermost layer (A0) had a pH from 3.6 to 4.3; in
only one case (nr. 19) was pH as low as 3.3 and in one (nr. 21) as
high as 4.4.
At greater depths and with diminishing proportion of humus pll
rises and reaches mainly 5.3—5.8 in 1—1.5 m. In layers deposited in
glacial rivers I have not reached the substratum in all cases. Fig. 5
represents such a case. pH here comes up to 6.3 in the layer with
subsoil water.
For studying Ihe root system of the oaks soil profiles have generally
been cut close to Ihe stems. A great number of roots run out more or
less horizontally near the surface of the ground in the A horizon and
the upper layers of the B horizon. In larger Irees a few roots are
moreover sent down to a greater depth, 1—2 m or still deeper. It seems to
be a characteristic feature that the roots that go down some distance
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