Earthworms and soil mesofauna as early bioindicators for landfill restoration

Landfill activities physically disrupt soil habitats, leading to the destruction of native soil biological communities and negatively impacting soil quality. Where landfill is restored to ‘soft’ end uses such as woodland, appropriate stockpiling and reapplication of native topsoil, or provision of a suitable soil habitat, may enhance soil fauna recolonisation and reduce restoration timeframes. Our aims were to identify the influence of reclamation practices on earthworm and mesofauna communities of two reclaimed landfill sites, and evaluate the role of earthworms and soil mesofauna as bioindicators of early landfill restoration success. We investigated soil physico-chemical parameters, and earthworm and soil mesofauna communities at two newly restored landfill sites and the surrounding land uses. Alongside traditional soil fauna community analyses, we applied the QBS-collembola (QBS-c) and QBS-earthworm (QBS-e) index techniques for the first time in a reclaimed landfill setting. Natural colonisation of reclaimed landfill by earthworms occurred rapidly where original site topsoil was stockpiled, reapplied, and revegetated following established best practice techniques for reclamation. Where best practice approaches were not followed (e.g., sowing grass cover, loose tipping, and sub-soiling), soil compaction and absence of ground vegetation cover were associated with extremely low earthworm populations. Both QBS-e and QBS-c index indicated that the most disturbed sites generally had the lowest soil biological quality. Mesofauna richness and abundance were generally higher in the low-disturbance sites compared to the surrounding land.; overall, reclaimed soils possessed lower springtail total abundance and species richness, and a mite community dominated by disturbance-specialist groups in relation to the surrounding land. Our findings demonstrate the value of recording a range of soil invertebrates during the investigation of land reclamation, since different soil bio