Review or “Hotspots of microbial activity induced by earthworm burrows, old root channels, and their combination in subsoil.
Hoang D.T.T. et al. Biol Fertil Soils 26 September 2016, generously shared by the authors on Research Gate.
Great article -- reports that Microbial Biomass and Soil organic matter is orders of magnitude increased in earth worm burrows as compared to bulk soil. Interestingly they show that the quality of the organic matter correlates with the microbial biomass. Also show that levels of critical nutrients like N and Phosphorous are significantly higher in the burrows where they increase the quality of the nutrients. They compared biopores made by worms with those, made by decaying roots and those made by root biopores with worms. The increase in microbial biomass is attributed not only to the increase in substrate but to the quality of the organic material that is created by earth worms as they process soil as shown by the superiority of the burrows inhabited by both decaying roots and worms.