Effects of earthworms on bulk density: A meta‐analysis

Abstract Although a comprehensive understanding of soil systems is needed to sustain soil functioning, our scientific knowledge of the underlying processes, for example, on the impact of earthworm activity on bulk density, is still limited. Using meta‐analysis, we quantified earthworm effects on bulk density and investigated the influence of driving factors. Earthworm effect sizes were species‐specific and depended on soil texture and earthworm body mass. Effect sizes were not unambiguously dependent on ecological groups, land use, experimental duration, abundance or initial bulk density. The paucity of data did not allow testing of interactive influences through meta‐analysis. Consequently, this study reveals important knowledge gaps in our understanding of earthworm effects on bulk density. Comparative studies taking the soil's complexity into account are still highly necessary to further our understanding of biotic interactions with soil‐structure dynamics. Highlights The effects of earthworms on bulk density were evaluated by meta‐analysis. Earthworm effects are species‐specific and depend on soil texture and earthworm body mass. Effects do not unambiguously depend on land use, duration, abundance and initial bulk density. Knowledge gaps regarding species, soil characteristics and interactive effects are identified.