Summary

obviously is related to the already mentioned reduction of factory operational
activity.
3.5.3. Pollution impact on the earthworm populations
Changes in the earthworm population in the sampling plots are related to the
factory emited pollution impact on the pine forest biocenosis. As evident from the
obtained data, in Saulkalne 1 and Saulkalne 2 the relatively high concentration of
calcium and magnesium in the soil does not have a direct impact on the earthworm
populations. The other way round, Saulkalne 2, where the highest concentration of
these metals in the soil surface was found, the highest total average all season
earthworm density was observed. It should be concluded that the calcium and
mangesium compund impact on the soil acidicity is more critical to the earthworm
populations. In all the sampling plots of transect the found soil acidity is relatively
low (Table 3.5). In the closest sampling plots to the emission source, it is evaluated
as a fairly acid- neutral or even alkaline. Also in the two furthest sampling plots, pH
values in the soil surface are relatively high and correspond to acid or moderately
acid soils. Due to the soil acidicity reduction, increases activity of microorganisms,
improves plant growth conditions, lowers proportion of C:N (Zelles et al., 1990), as
well as reduces the deliquescence of aluminium compounds and improves Ca and
Mg consuming to the soil organisms (Аристовская, 1980; Cronan, Grigal, 1995). In
the closest sampling plots to the emission source, the C:N proportion is favorable to
earthworms and other organisms of the soil. In the both furthest sampling plots, its
values are under 20, that indicates on the mineralization processes activization.
3.5.4. The earthworm communities structure in Saulkalne sampling plots
Comparing the density of Dendrobaena octaedra, no considerable differences
are observed in the sampling plots. In the furthest sampling plots routinely was found
another species of acidic soils- Dendrodrillus rubidus tenuis. The increase of the
population of this species in the forest areas where lime has been applied was
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