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INTRODUCTION Earthworms are considered as one of the most important biotic components of the soil. They participate in mineralization and breakdow of organic matter, in formation of the soil structure and humus, thus providing maintenance of the soil fertility. The significant importance of earthworms in these processes was emphasized already by C.Darwin (Darwin, 1881). During the course of several years earthworms may process all the surface of the soil through their digestive systems. In the intestinal tract of earthworms forms the so-called caprolite - a well structured mass of the soil and organic waste. In comparision with the surrounding soil, the casts are less acid, more humid, and they are richer in nutrients available to plants and microorganisms. Casts significantly improve physical and chemical properties of the soil. Earthworms is one of the most investigated animal groups in the world (Lee, 1985), however many of the functional aspects related to the earthworm activity are still uncertain. Lately, increases researcher interest on the effects of earthworm activities- both on the soil processes and in level of the ecosystem (Frelich et al., 2006; Coûteaux, Bolger, 2000). Earthworms are often reffered to as „engineers of the ecosystems” (Lee, 1985). Earthworms are sensitive to different agrotechnical and forestry acitvities, as well as to the anthropogenic pollution. They are an appropriate soil quality change bioindicator, as they are relatively less sensitive to the influence of different natural external factors (Christensen et al., 1987; Paoletti, 1999). In Latvia reasearches on earthworms are fragmentary and incomplete. The most significant researches have been conducted under guidance of V.Eglītis in the middle of the last century, covering mainly agricultural lands (Эглитис, 1954). In the seventies nearby Broceni cement plant, M.Šternbergs carried out observations on lime dust impact on the earthworm populations in natural forest biocommunities (Штернбергс, 1985). Since the ninties of the last century, the author of the doctoral paper at Biological institute of University of Latvia has carried out systematic reasearches on Latvia’s earthworm ecology. Researches have been carried out on the earthworm species structure and the population dynamic dependency on different 4
environmental factors, as well as on their bioindicative significance. The doctoral paper includes the author’s reasearch results on the earthworm species communities changes due to the agrotechnical activities in the most common agricultural soil varieties, as well as due to the industrial pollution and recreation in transformed pine forest soils, in all cases having regard to the fluctuations of meteorological factors as one of the major factors. In reasearches of agricultural communities agricultural soil monitoring data were used, in obtaining of whom the author took part during the period from 1992 to 1998. Researches on the effects of industrial pollution were carried out from 1989 to 1991 near Saulkalne dolomite processing plant. Researches on the recreation effects on earthworm species communities were carried out in the territory of Jurmala city from 1989 to 1990. The objective of the paper: The objective of the doctoral paper is to clarify the role of earthworms on the soil characterisation against a background of different antrophogenic factors interaction with natural environmental factors significant to this organic group, and to assess the bioindicative significance of earthworms. The tasks of the paper: - To clarify the structure of earthworm species communities in the most common agricultural soil varieties; - To clarify the impact of agricultural activities on the composition of earthworm species and quantity dynamics in agricultural lands in interaction with meteorological factors; - To clarify changes of earthworm species communities and their population density in pine forest soils transformed by calcium-containing emissions of the building material factory; - To clarify changes of earthworm species communities and their population density in oligotrophic pine forest soils due to the load of permanent recreation; - To evaluate the indicative significance of different parametres characterizing earthworm communities structure. 5
Page 1 and 2: UNIVERSITY OF LATVIA FACULTY OF GEO
Page 3: CONTENTS CONTENTS .................
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 and 20: 3. CHANGES OF EARTHWORM COMMUNITIES
Page 21 and 22: ubidus tenuis, whose propotion is i
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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