Establishment of Aporrectodea longa and measurement of dung carbon incorporation in soils under permanent pasture

• At three sites of recent Aporrectodea longa introduction dung incorporation was limited.
• At a fourth site, where A. longa had been present for a few decades more dung was detected at depth.
• For A. longa to influence bulk soil C their abundance needs to be higher than 50 m−2 and potentially close to 200 m−2.

Earthworm populations often have a large biomass in pasture soils and can significantly accelerate the disappearance of organic matter from the soil surface and its accumulation in soil layers. This field study investigated the influence of the anecic earthworm Aporrectodea longa on bulk soil C in permanent pastures two years after their introduction. We used the approach of measuring soil C and 13C after the application of C-enriched dung to paddocks with and without established A. longa populations (∼50 m−2). At three sites with differing soil types, dung incorporation into the soil was limited, suggesting that densities were still too low to influence bulk soil C. In a fourth pasture where A. longa had been present for 23 years, and had reached a density of 190 m−2, more dung-derived C was detected to 300 mm depth in the soil profile compared with the control without A. longa.