Soil mixing by earthworms can have a large impact on the fate of nutrients and pollutants and on the soil's ability to sequester carbon. Nevertheless, methods to quantify earthworm ingestion and egestion under field conditions are largely lacking. Soils of the Fennoscandian tundra offer a special possibility for such quantifications, as these soils commonly lack burrowing macrofauna and exhibit a well-defined O horizon with low bulk density on top of a mineral soil with higher density. Since ingestion-egestion mixes the two soil layers, the temporal changes in the bulk density profile of such soils may be useful for estimating field ingestion rates. In this study, we applied a model for earthworm burrowing through soil ingestion to observed changes in soil densities occurring in a mesocosm experiment carried out in the arctic during four summers with intact soil. The earthworms present in the mesocosms were , a, and (fourth season only). We show that changes in soil density profiles can indeed be used to infer earthworm ingestion rates that are realistic in comparison to literature values. Although uncertainties in parameter values were sometimes large, the results from this study suggest that soil turnover rates and endogeic earthworm soil ingestion rates in tundra heath and meadow soils may be as high as those reported for temperate conditions. Such large ingestion rates can explain observed large morphological changes in arctic soils where dispersing earthworms have resulted in complete inmixing of the organic layer into the mineral soil. Our approach is applicable to soil profiles with marked vertical differences in bulk density such as the soils of the Fennoscandian tundra where earthworms are currently dispersing into new areas and to layered repacked soil samples that are incubated in the field.

中文翻译：

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根据垂直容重分布的变化量化蚯蚓对土壤的摄入

蚯蚓混合土壤会对养分和污染物的命运以及土壤固碳的能力产生很大影响。然而，在野外条件下量化蚯蚓摄入和排泄的方法却很缺乏。芬诺斯坎苔原的土壤为这种定量提供了特殊的可能性，因为这些土壤通常缺乏穴居大型动物，并且在密度较高的矿质土壤顶部呈现出轮廓分明的低容重 O 层。由于摄入-摄入混合了两个土壤层，因此此类土壤的容重分布的时间变化可能有助于估计田间摄入率。在这项研究中，我们应用了蚯蚓通过土壤摄入挖洞的模型来观察在北极进行的中生态实验中土壤密度的变化，该实验在四个夏天使用完整的土壤进行。中宇宙中存在的蚯蚓是 、a 和（仅限第四季）。我们表明，土壤密度分布的变化确实可以用来推断与文献值相比更现实的蚯蚓摄入率。尽管参数值的不确定性有时很大，但本研究的结果表明，苔原石南和草甸土壤中的土壤周转率和内生蚯蚓土壤摄入率可能与温带条件下报道的一样高。如此大的摄入率可以解释在北极土壤中观察到的巨大形态变化，其中分散的蚯蚓导致有机层完全混合到矿质土壤中。我们的方法适用于容重垂直差异显着的土壤剖面，例如芬诺斯坎迪亚苔原的土壤，其中蚯蚓目前正在分散到新的区域，以及在田间孵化的分层重新包装的土壤样本。