Ilkka Markkula

Ojituksen ja NPK-lannoituksen vaikutus keidasrämeen maaperäeläimiin

Markkula I. Ojituksen ja NPK-lannoituksen vaikutus keidasrämeen maaperäeläimiin.

Tiivistelmä

The numbers of soil mites, springtails and enchytraeid worms were compared on virgin and forest-ameliorated parts of a bog in Lammi commune, southern Finland (N 61o 02’ E 24o 58’). The study site was an ombrotrophic raised bog with Calluna vulgaris - Empetrum nigrum - Sphagnum fuscum-hummocks and Eriophorum vaginatum - Sphagnum angustifolium-hollows. Part of the bog was drained in 1966 and fertilized in 1970 with urea (100 kg/ha) and PK-fertilizer for peatlands (400 kg/ha). The drainage had lowered the ground water level by 10-15 cm. The vegetation of the ameliorated site had also changed. Sphagnum-mosses had decreased but Eriophorum, Culluna, Empetrum and Pinus sylvestris growed more vigorously than on the virgin site. Samples were taken from both virgin and ameliorated part of the bog in may-november 1975 and may-september 1976. In the seasonal fluctuation of the three mite groups (Oribatei, Prostigmata and Mesostigmata) maximum numbers occurred generally in spring and autumn (figs. 1 and 2) with the exceptions of mesostigmatid and prostigmatid mites in the hollows of the virgin study site. No clear trends were found in the seasonal fluctuations of the numbers of Collembola and Enchytraeidae (figs 2 and 3). During the winter 1975-76 a severe decline occured in the numbers of enchytraeid worms. The reason was most probably the hard frost in early winter 1975 when the snow cover was thin and could not protect the animals. The oribatids did not suffer from the frost. In the mean numbers of oribatid mites there was no significant difference between virgin and ameliorated site. The numbers were slightly smaller in the hollows than in the hummocks (table 1). The numbers of mesostigmatid mites in the hollows were greater at the ameliorated site than at the virgin one. In the hummocks there was no difference between the sites. Upon the all remaining groups, Prostigmata, Collembola and Enchytraeidae, the forest-amelioration had a similar effect. These animals had increased in the hollows but at the same time decreased in the hummocks. At the virgin site, the hummocks seemed to be preferred microhabitat but at the ameliorated site more prostigmatid mites, springtails and enchytraeid worms lived in the hollows. A probable reason of the general decrease in the animal numbers in hummocks is that drainage makes the environment too dry for the animals. In the hollows, on the other hand, drainage and fertilizing probably had caused changes favourable for the animals. The oxygen content of the peat had increased and the quality of the litter improved from the viewpoint of soil invertebrates (more Eriophorum instead of Sphagnum-litter). Because five years had passed since the fertilization, the direct "shock-effect" of fertilizers most probably had no significance any more.

Vastaanotettu 31.10.2017 Julkaistu 1.1.1982

Katselukerrat 1181

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