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festuca polesica in denmark
357
found at Ihe Festuca polesica - stations, and therefore we come lo Ihe
conclusion that the species may be a rather recent immigrant, which
in future may extend its area in the most continental and dry parts
of Denmark (the Great Hel t- and Isef jord-areas). Another possibility
that the species formerly covered a larger and more close area and
owing to present infavourable conditions now only grows in a few
suitable places is much less probable. In the locality Klitborg the
occurrence of Festuca polesica coincides with an isolated station for
Cetraria nivalis, which according lo Böcher & Skytte Christiansen
has a split-up range in Denmark and is very rare. Nothing, however,
argues that Cetraria nivalis is a relic. Its occurrence at Klitborg is due
to the combination of gravelly poor soil and exposition lo the wind,
which in oilier places, e.g. on the island of Læso in the Kattegat,
characterizes the habitat of this lichen.
Andersson & Waldheim i 1946) have studied some South Swedish
communities very rich in Festuca polesica. Here the species grows
together with Koeleria (jlauca, Dianthus arenarius and Tortella inclinata
on sandy rather calcareous soils (pl! 7—8) or together with Koeleria
and Rhacomitrium canescens on circumneutral soils poor in lime. In
Germany and Czecho-Slovakia i( occurs in corresponding communities
[cp. Festuca glauca var. psammopliila - Koeleria glauca - Assoziation
described by Klika (1931) and Libbert 1932], Libberts community from
Neumarck is developed on moderately acid and sandy soil and is referred
lo the Corgnephorion. The plant lisl, however, contains a great number
of continental species which are here called »Begleiler». The more
exclusive species (Assozialionscharakterarten) are likewise continental,
while almost all typical plants of the Corgnephorion have a suboceanic
distribution. In Central Europe as well as in the localities described
by Andersson & Waldheim Festuca polesica grows in grasslands which
may belong to Ihe steppe-alvar group and not to the main group of
West European dry grasslands ((]orijriephoriis-group). In Denmark, on
the other band, Festuca polesica partly occurs in communities with
predominance of continental and subcontinental species (Tab. 1, nos.
3—4) partly in such with predominance of suboceanic dry soil species
(nos. 1—2). Furthermore, as already mentioned, it grows on rather
markedly acid soil. This is a very peculiar feature and an interesting
deviation from the rule that continental plants at their western limits
prefer or select calcareous soils (see examples in Böcher, Christensen
& Skytte Christiansen). Festuca polesica is a continental dry soil
plant which as to Ihe hydrogen ion concentration of the soil is rather
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