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We studied the effect of the deep-burrowing earthworm Lumbricus terrestris on the greenhouse gas (GHG) fluxes and global warming potential (GWP) of arable no-till soil using both field measurements and a controlled 15 week laboratory experiment. In the field, the emissions of nitrous oxide (N2O) and carbon dioxide (CO2) were on average 43 and 32% higher in areas occupied by L. terrestris (the presence judged by the surface midden) than in adjacent, unoccupied areas (with no midden). The fluxes of methane (CH4) were variable and had no consistent difference between the midden and non-midden areas. Removing the midden did not affect soil N2O and CO2 emissions. The laboratory results were consistent with the field observations in that the emissions of N2O and CO2 were on average 27 and 13% higher in mesocosms with than without L. terrestris. Higher emissions of N2O were most likely due to the higher content of mineral nitrogen and soil moisture under the middens, whereas L. terrestris respiration fully explained the observed increase in CO2 emissions. The activity of L. terrestris increased the GWP of field and laboratory soil by 50 and 18%, but only 6 and 2% of this increase was due to the enhanced N2O emission. Our results suggest that high N2O emissions commonly observed in no-tillage soils can partly be explained by the abundance of L. terrestris under no-till management and that L. terrestris can markedly regulate the climatic effects of different cultivation practises. [ABSTRACT FROM AUTHOR]

Abstract: Macroporosity of soil and earthworm abundance in relation to the distance from subsurface drain lines were determined to investigate the effect of subsurface drainage on the spatial variation of clay soil structure. Our hypothesis was that soil macroporosity near a drain line location would be greater than the macroporosity at a midpoint between two drain lines where the groundwater table remains theoretically at a higher level. The experimental site was located on a post-glacial clay soil classified as a very fine Aeric Cryaquept (Vertic Cambisol). The area of the field was 1ha and the slope varied from 2 to 4%. Measurements of soil properties were carried out along four subsurface drain lines installed 50 years before soil sampling. In each drain line, vertical soil profiles were examined at different distances from the drain: (1) above the drain, (2) 2m from the drain, and (3) midway between two drains (6–7m from a drain). In each vertical profile, soil macroporosity, number of earthworm burrows and root channels, and saturated hydraulic conductivity (K sat) were determined in three soil layers to the depth of 50cm. In addition, the field saturated hydraulic conductivity (in situ) and the number and fresh mass of earthworms were determined. The results showed that the number of earthworm burrows was 44% (90 burrowsm−2) greater above a drain than at a distance of 6–7m from the drain. There was also an indication of higher earthworm density above the subsurface drains than between them. The other measures of soil physical properties were not clearly related to distance from the drain. One reason for the small differences in soil properties in relation to drain position was probably the groundwater level that in our clay field varied less in relation to drain location than was expected. Spatial variation of the investigated soil properties was mostly explained by the slope of the field. Even though the groundwater table was shallower at the downslope part compared with the upslope part of the field, the number of biopores, K sat and the number of earthworms clearly increased downslope. [Copyright &y& Elsevier]

Sampling strategy, in terms of physical size and positioning of the sampling units, may affect strongly the results of spatial surveys. The aim of this study was to analyse the effect of sampling unit size on the perception of spatial patterns of earthworm (Lumbricus terrestris L.) middens. The implications for optimal sampling strategy for spatial interpolation were assessed. Spatial variation of midden density was investigated in Vaisakko forest, south-western Finland, using 225 sample points distributed on a square grid with a minimum distance of 25 m between samples. At each point, middens were counted within samples of sequentially increasing size (sample surface 0.125, 0.25, 1 m2) and analysed by means of geostatistics. The results showed significant spatial continuity of midden distribution in all cases. Whereas, neither the estimate of mean middens density nor the global distribution pattern were markedly affected by sample unit size, the total variance increased considerably with decreasing sample unit area. Isotropic variograms for different sample unit sizes were all spherical but large discrepancies in the model parameters were observed. The nugget variance tended to decrease with increasing sample unit size while the spatial variance increased slightly. Since changing sample unit size affected the variogram we also investigated the consequences in terms of optimal sampling strategy for spatial interpolation by punctual kriging. Increasing the quadrat size from 0.25 to 1 m2 and simultaneously increasing the sample spacing from 25 to 50 m, so that the sampling effort was constant in terms of total surface investigated, did not affect the kriging standard deviation. The positive effect of increasing quadrat size was thus enough to compensate the negative effect of the correspondingly sparser sampling grid. The results showed that while the sampling unit size did not have strong effect on the perception of general midden distribution in the forest, it did have marked consequences in the spatial modelling of the phenomenon. The issue of sampling unit size is clearly worthy of careful consideration in the planning of field studies and geostatistical tools can be put to good use in evaluating the pros and cons of different sampling strategies. [Copyright &y& Elsevier]

The Hebrides of Scotland constitute a unique set of island environments with a long history of human settlement and agriculture. Earthworm community surveys were undertaken in selected agricultural landscapes of Inner (Isle of Rum) and Outer (North and South Uist) Hebrides. On North Uist, earthworms were sampled from areas of Blackland (organic, anthropic, acidic agricultural soils) and on South Uist in machair (sandy, fertile, low-lying grassy pasture). Specific grassland and cultivated areas with various organic additions - including dung and seaweed - were targeted, using hand-sorting of soil for earthworms plus mustard vermifuge extraction. Work on Rum investigated earthworms in ridge and furrow (lazybed) agricultural systems, abandoned almost 200 years ago and since uncultivated, but grazed by ungulates. On the Uists, nine earthworm species were identified, representing all three ecological categories, but dominated by the epigeics, Dendrobaena octaedra and Lumbricus rubellus. Densities and biomasses across Blackland soils ranged from 10-130 ind. m−2 and 2.3–33.7 g m−2, respectively. Here, 5 species were present, and management had a significant effect on species richness and abundance with most earthworms present in recently restored lazybeds. In the machair soils, the corresponding measurements were 4–220 ind. m−2 and 0.8–89.0 g m−2. Significantly higher earthworm densities and biomasses were recovered below cattle dung pats compared with dung-free areas. Cultivated areas in machair were less diverse and had lower earthworm densities than uncultivated. On Rum, ridge and furrow abundances did not differ clearly with 24–102 and 34–112 ind. m−2 respectively and biomasses of 7.4–26.3 and 8.8–30.8 g m−2. Here, Aporrectodea caliginosa (49%), L. rubellus (23%) and Dendrodrilus rubidus (19%) dominated of the seven species found. Further research on earthworms in the Hebrides is warranted. • In abandoned lazybeds, ridges and furrows were similar for earthworm abundance and biomass. • OM addition to Blackland soils increased epigeic numbers and biomasses four-fold. • In machair soils, dung presence supported higher earthworm abundance. • Hebridean earthworms benefit from brown seaweed and dung application. [ABSTRACT FROM AUTHOR]

Abstract: An inoculation of the deep burrowing earthworm Lumbricus terrestris L. was carried out for soil amelioration purposes at an arable field on heavy clay in southern Finland. L. terrestris, whilst entirely absent from the field and its immediate surrounding, was present in many other local soils. Prior to inoculation, field management was changed in favour of L. terrestris by improving the subdrainage and by implementation of reduced tillage. In Autumn 1996, 82 earthworm inoculation units (EIUs) were introduced in three transects at one end of the field, one transect lying within a permanent grass strip outside the cultivated area. In Autumn 1998, L. terrestris had persisted outside the cultivated area with maximum density of 28 ind. m−2 (median: 0 ind. m−2). No individuals were found inside the field. In Autumn 2003, maximum density was 43 ind. m−2 (median: 9 ind. m−2) outside the cultivated area, with evidence for 8 m dispersal from inoculation points (1.1 m year−1). In 2003 individuals were also found in low densities inside the field, close to subdrains, with a maximum density of 4 ind. m−2. Results call for critical evaluation of this inoculation practice. [Copyright &y& Elsevier]