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Density-Mediated Earthworm Effects on Soil Respiration

Uvarov A. V.

Polish Journal of Ecology

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2016

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Vol. 64, nr 4

534--546

EN

Earthworms, as ecosystem engineers, strongly regulate microbial activities and microorganism-mediated processes in the soil; their effects differ among species and ecological groups. Lumbricids are suggested to have density-dependent regulation of species populations, but it is not known whether their effects on soil processes are density-dependent. In a field experiment, litter/soil microcosms contained monocultures of five common lumbricid species belonging to epigeic, anecic and endogeic ecological groups, at various density levels. After 6 and 15 weeks, respiration rates of soil systems were measured and (after subtraction of approximately calculated earthworm respiration) microbial respiration rates estimated. In the presence of earthworms, respiration of soil systems tended to increase. After 6 weeks, this increment was explained by earthworm's own respiration. However, after 15 weeks earthworm respiration comprised 12–80% of the respiration increment; hence, microbial respiration was stimulated by earthworm activities. In any earthworm species, total community and microbial respiration were correlated with its density increase. However, specific respiration increments (per unit earthworm biomass) were not significantly affected by lumbricid density. The lack of density-dependent patterns indicates a weak impact of lumbricid intraspecific interactions on soil respiration. However, specific respiration increments and stimulation of microbial respiration varied across earthworm species, being higher for endogeic than for epigeic/anecic species. This is explained by a relatively lower microbial grazing by endogeics and a depletion of litter (a resource and environment for the microbial community) by epigeic/anecic earthworms. Overall, the results support the view that microbial community adapts to the presence of earthworms by switching to a smaller, but a more active one.

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Landscape Patch Pattern Effect on Relationships between Soil Properties and Earthworm Assemblages: A Comparison of two Farmlands of Different Spatial Structure

Regulska E., Kołaczkowska E.

Polish Journal of Ecology

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2015

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Vol. 63, nr 4

549--558

EN

Our survey was carried out in two study sites of approximately 3.3 ha each located in the Suwałki Lake District in NE Poland in the year 2008. Earthworms and soil samples were collected during two campaigns (spring and autumn) from 25 × 25 cm and 30 cm deep sampling points. The complex arable landscape (CAL) supported higher earthworm diversity, density and biomass than the similarly managed but homogeneous arable landscape (HAL). The spring and autumn earthworm sampling campaigns revealed very different patterns, and we conclude that autumn sampling is the most adequate for biomonitoring. On the other hand, the spring collections were significantly correlated to soil physical parameters, thus spring sampling is more suitable for studying such correlations. Significant correlations occurred almost exclusively for CAL and the soil parameters significantly relating with earthworm community were: soil moisture, nitrogen and organic carbon contents. The possible reason for it is the presence of numerous refuges for lumbricids offered by field margins, balks, woodlots and meadows in the CAL and lack of them in the HAL.

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Earthworms (Lumbricidae) as bioindicators : the relationship between in-soil and in-tissue heavy metal content

Tischer S.

Polish Journal of Ecology

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2009

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Vol. 57, nr 3

513-523

EN

The heavy metal (Cd, Zn, Cu, Pb, Ni, Cr) accumulation in earthworms was measured and evaluated on 84 differently managed and polluted sites (field, grassland, deciduous forest, coniferous forest, alluvial sites, mine spoil) together with selected soil properties, like pH and C[org]-contents. The uptake of heavy metals by the earthworms was correlated with in-soil metal amounts and it showed a considerable variation between land use types and the individual lumbricid species. An important positive correlation was determined between in-tissue contents of earthworms and in-soil contents for all studied heavy metals: Cd (R[^2] = 0.72), Cu (R[^2] = 0.65), Cr (R[^2] = 0.54), Pb (R[^2] = 0.51), Zn (R[^2] = 0.47), Ni (R[^2] = 0.45). Mostly Cd and Zn are accumulated by earthworms. The uptake of Cd and Zn by epigeic earthworms is stronger than by other endogeic and anecic species. The highest metal amounts of Cd were accumulated in the following species: Aporrectodea caliginosa (Savigny) (18 mg kg[^-1] dw) Lumbricus castaneus (Savigny) (17 mg kg[^-1] dw), Octolasion cyaneum (Savigny) (17 mg kg[^-1] dw), Lumbricus rubellus (Hoffmeister) (14 mg kg[^1] dw). The highest uptake of Zn was found for the species: L. castaneus (623 mg kg[^-1] dw), Lumbricus terrestris (Linnaeus) (433 mg kg[^-1] dw), A. caliginosa (416 mg kg[^-1] dw), and L. rubellus (339 mg kg[^-1] dw). The lowest contents of Cd (3 mg kg[^-1]dw) were calculated for Aporrectodea longa (Ude) and for Zn - Allolobophora chlorotica (Savigny) (168 mg kg[^1-] dw). Transfer ratios (TR) (ratio of in-soil heavy metal content to the in-tissue metal content in earthworms) ranged for Cd - from 6 in alluvial forest sites to 64 in coniferous forest sites and for Zn - from 2 in alluvial grassland to 12 in coniferous forest. Cd and Zn are more strongly taken up by the epigeic species like Dendrobaena octaedra (Savigny) (TR: Cd = 47, Zn = 8), L. rubellus (TR: Cd = 21, Zn = 5), and L. castaneus (TR: Cd = 12, Zn = 5) than by the other endogeic and anecic species, with TR values accounted from 9 to 21 for Cd and 2 to 5 for Zn, respectively. For risk assessment of habitats cadmium is the more important heavy metal due to its high transfer rates into the tissues of earthworms.

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Lumbricidae communities in soil monitoring sites differently managed and polluted with heavy metals

Tischer S.

Polish Journal of Ecology

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2008

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Vol. 56, nr 4

635-646

EN

Species composition, density and biomass of earthworms were studied on 84 differently managed and polluted sites (field, grassland, deciduous forest, coniferous forest, alluvial sites and mine spoil). All these sites are constantly monitored since a decade. In 13 sites amounts of heavy metals increased from: Cd - 3 to 6 mg kg[^-1], Zn - 303 to 606 mg kg[^-1], Pb - 95 to 317 mg kg[^-1], Ni - 31 to 55 mg kg[^-1], Cr - 58 to 80 mg kg[^-1], and Cu - 59 to 114 mg kg[^-1] soil, that is up to 2000, 880, 1090, 295, 320, and 520% higher, respectively, than in unpolluted field sites. Results show that metal pollution is not a dominating factor determining the species diversity and densities of earthworms. Remarkable differences in the distribution of ecological groups were found between biotope types. The endogeic species (Aporrectodea caliginosa Savigny, Aporrectodea rosea Savigny, Allolobophora chlorotica Savigny, Octolasion cyaneum Savigny) dominate in field and grassland habitats. The anecic species (Lumbricus terrestris L., Aporrectodea longa Ude), however, appear mostly in grassland. Epigeic species (Lumbricus rubellus Hoffmeister, Lumbricus castaneus Savigny, Dendrobaena octaedra Savigny) are found exclusively (in addition to the other two life forms) in grassland and the forest habitats. Differences in earthworm biomass between monitoring sites are not related to ecological risk assessment. These differences may be largely dependant on soil properties e.g. pH and organic matter. A matrix with the ecological requirements of earthworm species was developed.