Summary

soil liming has facilitated great bulk of calcium and mangesium descending into the
forest soils. Due to what reduces acidity in the upper layer of the soil, changes the
upper layer structure and humus matter, and increases biomass of live organisms
(Мелецис, 1985; Laiviņš et al., 1993).
Most of the pine forests in Latvia are oligotrophic and mezotrophic dry forests.
In such forest types, mostly in suburbs and in towns, forest transformation processes
are more evident. Natural pine regeneration in such transformed forests is negligible.
Forest transformation is directly related to gradual eutrophication of the soils, due to
which increases the nutritient amount necessary to plants; and is related to reduction
of acidity, which significantly facilitates introduction of new species. The boreal
forests (Vaccinio vitis idaea-Pinetum, Vaccinio myrtilli-Pinetum) transform into
societies of much wider ground cover and underbrush content (Sambuco recemosae-
Pinetum). Forests become more shady and humid. The typical raw humus changes,
forming a transition form (moder humus) between mor and mull humus (Laiviņš,
Laiviņa, 1991; Laiviņš, 1998).
3.4. Earthworm species communities changes due to transformation of Jurmala
forest soils
3.4.1. Description of the sampling plots and sampling procedure
For the sampling plots was chosen Vaccinio myrtilli – Pinetum forest growth
type. In little transformed pine stands underbush and moss layer is well outlined,
whereas the transformed stands are easy to recongise for the uncharacteristic species
content and structure- dense bush, broad-leaved tree sprouts and vascular plants. It
allows both to assess the transformation level of the pine forests and to display main
stages of antropogenic succession (Laiviņš, 1998).
Earthworm material was sampled in September 1989 and May 1990 and
September of the same year, in the sampling plots of different eutrophication stages.
Sampling areas were chosen of similar relief location, humidity conditions, forest
stand age (middle age and adult stands) and soil composition. Soil type- typical
podsol on sand.
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