Assessing earthworm diversity and population dynamics in agroecosystems

Earthworms play a fundamental role in the maintenance of soil health, and managing agroecosystems in ways that help earthworm populations to flourish is increasingly being recognised as a possible way to tackle the global issues of soil degradation and food insecurity. In order for this to become a reality, existing knowledge gaps surrounding the effects of different land use practises on earthworms need to be addressed. In addition, better management of earthworm populations will require more
extensive population monitoring, as to date they have been severely under-recorded. This thesis aims to investigate how changes in land use, particularly temporary arable conversion to ley, affect earthworms in agroecosystems. It also aims to demonstrate the feasibility of a novel soil eDNA sampling technique for monitoring their populations, and assess its effectiveness relative to traditional methods. To do this, a novel mesocosm experiment was performed which investigated how earthworm activity and population variables respond to different land use practises, under varying climatic scenarios. Earthworm eDNA sampling in the field was also carried out alongside traditional hand-sorting, and laboratory experiments investigated earthworm population responses and associations with other soil quality indicators. Consistent positive effects of arable to ley conversion on earthworms were found, indicating that ley farming can significantly boost earthworm activity, abundance, biomass and diversity across short time scales. eDNA sampling also proved to be an effective tool for monitoring earthworms in agroecosystems, which found more species per sample when compared with hand-sorting. The eDNA technique was able to detect fine-scale changes in arable earthworm communities bought about by recent conversion to ley, indicating that it could also be a useful tool for monitoring the effectiveness of changes in land use aimed at improving soil health. Taken together, the results in this thesis offer new insights into the protection, restoration and monitoring of earthworms in agroecosystems, whilst also highlighting the need for greater consideration of these important animals and opening up new avenues for future research.