Rit (Vísindafélag Íslendinga) - 01.06.1975, Page 121

river banks. Particularly noteworthy here is the abundance of
Anthoxanthum odoratum which comes close to the character spe-
cies in physiognomy and covering. Salix glauca occurs to a greater
extent than usual. Analyses 9 is from Nefsholt in Holt, from the
bank of a stream in a well sheltered spot. Analyses 10 is from the
vicinity of a drainage canal in Flói where a Carex mire has been
drained. Most of the principal species of the Carex mire have been
drastically reduced or completely disappeared by the drainage, but
Equisetum has increased and gramineous vegetation has taken root
in the sociation. C. nigra has been best preserved, but is, however,
much less noticeable than before. This development can be traced
through its stages from the canal into the mire tract which has
not been affected by the drainage. It is most surprising of all how
rapidly this transitional cycle has been completed, for the drainage
canal was only 4-5 years old when the observation was made. The
abundance of Agrostis canina is characteristic, but this is always
the first gramineous species to benefit from the draining of mires.
Analysis 11 is from damper ground than usual for this sociation.
This is clearly indicated by the increased HH percentage.
69. E. palustre — C. nigra sociation
(Tab. XV A-B 1-7)
The observations of this sociation are from Húnavatnssýsla, Rang-
árvallasýsla, Vopnafjörðm-, Snæfellsnes and Eyjafjörður. There are,
however, no analyses available from the area last mentioned, but
the sociation is widely distributed throughout Eyjafjörður. The so-
ciation is closely related to the preceding one, 68, and it mostly
consists of the same species, with the exception of the gramineous
vegetation which is much less here.
The biological spectrum is markedly different. The A percen-
tage becomes higher here than the E percentage. Ch occurs to some
extent, and the H percentage fluctuates more in the analyses. This
sociation thrives in more varied moisture conditions than 68. Some
areas are quite moist, but it also occurs in the driest mire tracts.
Analysis 1 is from Helguhvammur in Vatnsnes. There the sur-
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