Earthworm community development in organic matter-amended plots on reclaimed colliery spoil

Abstract

Earthworms were sampled at a semi-restored colliery spoil site at Chisnall Hall in Lancashire, two and a half years after the site had been experimentally treated with a number of organic matter applications of anaerobic digestate and compost-like output, in isolation and in combinations. This gave six treatments including a control with no amendment. The material was mechanically dug into the site into replicated 20 x 10 m plots. Within each plot, 4 types of plant, ash, cherry, willow and reed canary grass, were introduced. Results showed that all organic treatments gave rise to significantly higher community densities of earthworms, with the greatest (638 earthworms m-2) in the high digestate application (1875 t ha-1) treatment, compared with 192 earthworms m-2 in the un-amended control (p<0.05). Species that contributed to greatest numbers were Allolobophora chlorotica (the green worm) and Aporrectodea caliginosa (the grey worm), both shallow-working, and Aporrectodea longa (the black-headed worm), a deep burrower. Nine earthworm species were encountered in total. Planting type had no significant effect on earthworm density. Addition of organic matter to a colliery spoil site greatly enhanced earthworm community density, through a combination of immigration from surrounding areas and increased reproduction.