In many arable soils, earthworms form the key component of the soil animal community and greatly contribute to soil quality. Our goal was to identify variables that can explain the variation of earthworm communities across Finnish arable fields by focusing on both regional aspects, such as climate and inherent soil properties, and local aspects, such as field management practices and field margins. We sampled the earthworms during the autumn of 2004 and 2005 at 53 sites of cultivated fields and margins, distributed to 11 localities ranging from the southern parts of Finland to the Arctic Circle. Simultaneously, information was collected on topsoil properties, cultivation history, and climatic factors. We found that soil type was by far the best regional variable to explain the variation in total earthworm density, the density being highest in medium coarse soils, i.e., silts and very fine sands. However, soil type had a significant interaction with soil C:N ratio. After accounting for the effect of soil type, no clear geographical trends remained in the regional variation, except that coastal areas with thin snow cover and deep frost had lower earthworm density than inland areas with deep snow cover and shallow frost. Of the local variables, tillage frequency, grazing, and field margins were the most influential. Frequent tillage led to earthworm communities heavily dominated by endogeic species, while grazed pastures had more than three times the earthworm biomass in comparison to non‐grazed fields. Field margins harbored over twice the density and almost double the number of species in comparison to the adjacent cultivated fields, and eight of the nine species had wider regional distribution in the margins than in the fields. Inside the fields, species richness tended to decrease gradually with increasing distance to the margin. Our results suggest that, while soil texture and climatic factors set the general limits to earthworm communities in Finnish arable soils, field management practices can override these limits at the local scale. Cultivation in general simplifies the earthworm community, and this is particularly clear in the fields that are frequently tilled, whereas pastures and field margins seem to effectively preserve the biomass and diversity of earthworms.

No abstract

No abstract

No abstract

Abstract.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 (N 2 O) and carbon dioxide (CO 2 ) 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 (CH 4 ) were variable and had no consistent difference between the midden and non-midden areas. Removing the midden did not affect soil N 2 O and CO 2 emissions. The laboratory results were consistent with the field observations in that the emissions of N 2 O and CO 2 were on average 27 and 13 % higher in mesocosms with than without L. terrestris. Higher emissions of N 2 O 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 CO 2 emissions in the laboratory. In the field, the significantly elevated macrofaunal densities in the vicinity of middens likely contributed to the higher emissions from areas occupied by L. terrestris. 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 N 2 O emission. Our results suggest that high N 2 O emissions commonly observed in no-till 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.