Ársrit Ræktunarfélags Norðurlands - 01.01.1975, Page 41

ENGLISH SUMMARY
In the years 1969----1973 studies of the soil fauna were carried out at
the field station Katla, situated on the west side of Eyjafjörður, Nortli-
Iceland.
Samples were taken from special plots with different vegetation
cover and from some other sites selected in relation to vegetation,
altitude etc. The depth of the samples was 2.5 cm, the areal 20 cm2,
the volume 50 ccm. In most cases two series of 5—6 samples were tak-
en in successive depths or at regular intervals, one for arthropods (insect
larvae, Collembola and mites), the other for worms and worm-like
animals. Classical methods were used for extraction (Tlullgren and
Baerman apparatus respectively) Counting was done on a counting
plate by aid of a stereo-microscope.
The results are represented in Tables 1—7. In Tbs. 1—5 the samples
from each of the vegetation complexes are grouped together, the
numbers being the sum of animals counted in the whole section of
5—6 samples, i. e. the number per 20 cm square. Average numbers per
20 cm2 and 1 m2 are also showed at the end of the tables. For the
Nematods two numbers are usually presented, one (a) is the counted
number, the other (b) is a caculated number.
In Table 6 the average numbers per square metre from the five
vegetation types are compared. The highest number in each animal
group is underlined. The total number of animals is highest in the
hay field (tún), owing to a very high number of Collembola, which must
be rather exceptional. The mites are most numerous in the heath
vegetation, and so are also the Nematoda according to the calculated
numbers. Insect larvae, Enchytraeidae (potworms), and Rotatoria
(Rotifers) are most numerous in the bogs, and Crustaceans are only
to be found there. The lowest total number, however, is to be found
in the mires, owing to a low number of Nematoda there. The average
number of Collerribola and mites is nearly equal in the five vegetation
types.
In Table 7 the average numbers of animals in different depths is
presented for three main types of habitats, i. e. hay field, heath, and
bogs. If the Nematoda are neglected, more than half the total number
of animals is to be found in the uppermost layer of 2,5 cm, which is
the sward layer, very rich in plant remains.
Most animal classes do not penetrate beneath 10 cm, although mites
and Collembola may be found down to 17 cm in a moderately wet soil.
The Nematoda are much more evenly distributed in relation to depth
than other soil animals observed in the present study, and they do
penetrate at least down to 45 cm.
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