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earthworm species were found in density up to 164 worm m -2 (Ventiņš, 1991). In Luthuania’s pine forests were found 4 earthworm species. The dominant is Dendrobaena octaedra up to 3 worm m -2 . Is mentioned negative effect of conifers on earthworms (Атлавините, 1976). T. Timm (Timm, 1970; 1999) indicates on Dendrobaena octaedra and Lumbricus rubellus as the domimant species in Estonian coniferous forests. Routinely found is also Dendrobaena octaedra and Lumbricus rubellus, but in deciduous forests- Dendrobaena octaedra and Lumbricus rubellus. In the coniferious forest of North-West Russia the dominant are such species as Dendrobaena octaedra and Lumbricus rubellus in density up to 1 - 7 worms m -2 . It is possible that earthworms in the Western lowlands of Russia spread from the Eastern coast regions of the Baltic Sea. Freeze resistance, parthenogenesis, acido-tolerance, ability to feed on low quality food, made such species as Dendrobaena octaedra suitable to colonize the acid soils. With earthworms spreading into the forest soils, organic and mineral soil horizons were gradually mixed (Tiunov, et al., 2006). With change of the climate in the postglacial period and spread of deciduous tree species, podsol began to change to the brown soils. That enabled also introduction of other earthworm species (Räty, Huhta, 2004). The big endogeic earthworms, e.g., Aporrectodea caliginosa, have greater impact on soil processes than the epigeic species however their spread in the boreal pine forests is restricted by soil acidity and freeze. In Finland’s pine forests (type Vaccinum) dominance of Dendrobaena octaedra is almost of 85%. That is a species with the widest habitat spectrum, however, in greater density it usually is found in richer forest types, soils treated with lime, or in forests with great admixture of deciduous trees. However, in the pine forests, earthworm density is not greater than 4 – 36 worms m -2 (Haimi, Einbork, 1992). In Sweden’s and Norway’s pine forest soils (soil pH 3.5 – 4.5), the dominant are Dendrobaena octaedra, Dendrodrillus rubidus tenuis, seldom Lumbricus rubellus 1,4 - 20 worms m -2 . Other species are rarely found (Abrahamsen, 1972; Persson, 1988). According to the observations of the author of the doctoral paper (unpublished data), in Sweden’s central part pine forest areas alongside with Dendrobaena octaedra usually is found also Dendrodrillus 20
ubidus tenuis, whose propotion is increasing in the forest areas terated with lime. 3.2. Earthworm fauna changes due to forest liming Although the boreal pine forest eutrophication and trasnformation processes may be observed close to every bigger city of Northern and Central Europe, as well as in territories where dynamic optional acctivities are being applied, therefore the literature lacks of data on what effect do such changes have on the soil animals, and, what is the possible soil animal impact on these processes. In Western Europe the pine forest transformation problems are being considered by another point of view, that is, in relation with forest liming, which is being implemented in order to improve tree growth in poor soils and to reduce soil acidity caused by pollution (Robinson et al., 1992a). Several essential factors for earthworms are being changed by lime applicationsoil acidity, content of calcium changes appear in microorganism consistence, which are the potential nutritients, and others. After lime application, the earthworm density as a rule increases. In Finland, after forest treatment with lime, esentially increased population of Lumbricus rubellus, while population of Dendrobaena octaedra did not change. It was observed that presence of Aporrectodea caliginosa reduces population of Dendrobaena octaedra (Persson, 1988; Robinson et al., 1992). Usually the most important reason of live animal population density increase is the improvement of the nutritient base, or changes in the mutual competition of live organisms (Persson, 1988). After lime application, reduces proportion of C:N in the organic horizon of the soil (Zelles et al., 1990). Proportion C:N is one of the most important earthworm population limiting factors (Lee, 1985). Conifers, moss and lichen contain considerably less N and mineral substances than decidious trees and vascular plants (Аристовская, 1980). Presence of vascular plant remains in O horizon’s considerably favours increase of earthwomn population (McLean et al., 1996). If soil acidity reduces, nitrogen mineralization happens faster, and increases contrentation of the available nitrogen forms in the soil (Robinson et al., 1992a). Earthworms facilitate different processes in the soil, including also formation of 21
Page 1 and 2: UNIVERSITY OF LATVIA FACULTY OF GEO
Page 3 and 4: CONTENTS CONTENTS .................
Page 5 and 6: environmental factors, as well as o
Page 7 and 8: Aprobation of te Results Te results
Page 9 and 10: 1. EARTHWORMS IN AGRICULTURAL LANDS
Page 11 and 12: Summing up data of numerous researc
Page 13 and 14: 1.3. Earthworm impact on gricultura
Page 15 and 16: period. The samples were hand sorte
Page 17 and 18: Figure 2.1. All season mean density
Page 19: 3. CHANGES OF EARTHWORM COMMUNITIES
Page 23 and 24: soil liming has facilitated great b
Page 25 and 26: 3.4.2. The total earthworm populati
Page 27 and 28: population of earthworms in all of
Page 29 and 30: of Aporrectodea caliginosa, emerge
Page 31 and 32: Table 3.5 The chemical properties o
Page 33 and 34: For the reciprocal comparision of t
Page 35 and 36: observed by the author of the docto
Page 37 and 38: Figure 3.3. Possible process of pin
Page 39 and 40: CONCLUSIONS 1. Reasearches conducte
Page 41 and 42: LITERATURE Abrahamsen, G. 1972. Eco
Page 43 and 44: Latvian Academy of Sciences, B, 7 (
Page 45: беспозвоночныхмор

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