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BIDRAG TILL SKÅNES FLORA 37. QUERCUS PKTRAEA
201
in »usually poorer ground here and there everywhere» (transl. from
the Swedish).
In the preceding pages it has been emphasized that Q. petraea
occurs within the province of Skåne for the most part in precipices,
upper slopes and hill tops. This seems to be the rule also in other parts
of the distribution area (Krasan 1886, Moss 1913, Salisbury 1918,
Salisbury & Tansley 1921, Seitz 1924—26, Tansley 1939), and may
be a parallel phenomenon to its preference for coarse material (Büsgen
1911, Olsen 1938, Tansley 1939). In localities of this type the ground
is often leached (Salisbury & Tansley 1921, Tansley 1939), and the
upper layers are more or less deficient in water. Q. petraea is in
accordance with these ecological features more xeromorphically organized
than is Q. Robur. The leaves are thick, bright and shining on the upper
surface and covered with stellate hairs beneath.
Soils of the type described above have an acid reaction, and on
account of the stronger leaching this is more pronounced in regions
with a higher precipitation (Salisbury & Tansley 1921, Tuxen 1937,
Tansley 1939). The effect of the oceanic climate on the soil — the
formation of raw humus and the leaching — may have a greater
ecological influence on the development of the sessile oak than has the
direct climatic effect, apart from the duration of the winter. These
conditions apply not only to Q. petraea but very probably also to most
of our suboceanic species, for with few exceptions they are confined
to soils poor in nutrition. As has been pointed out by Mård (1924)
the areas of the suboceanic species in reality correspond very much to
(hose of the oligotrophic types.
The distribution of Carex magellanica and C. pauciflora, two
pronouncedly oligotrophic species, is illuminating in Ibis connection.
These species, which are index species in the poor fens of the province
(Waldheim & Weimarck 1943), have an area in Skåne practically
identical with that of the sessile oak.
The province of Skåne is situated in the border land between the
Suboceanic Flora province and the more continental »Middle Baltic»
province. The precipitation is rather low. The yearly rainfall reaches
800 mm furthest to the north, in the south-west it only amounts to
500 mm. During the summer season (May—October) the rainfall is
highest in the north-western corner, 450 mm, lowest in the
southwestern, 300 mm (Wallén 1945). The humidity is higher in north
and central Skåne than along the coast [Hesselman 1932). On account
of the relatively low rainfall only the pure gneiss moraines in the
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