Addition of composted green waste and ericoid mycorrhizal fungi fails to facilitate establishment of Atlantic heathland species

Abstract

Post‐mining restoration of heathland habitats has met with mixed success. Failures are often ascribed to the complexity of replicating soil conditions: a scarcity of organic matter and microbial symbionts in stored overburden used for restoration is frequently implicated. Nonetheless, systematic investigation of the role of both interventions is lacking. Using a greenhouse trial and a large‐scale field experiment within a commercial kaolinite mine site, we explored how the addition of ericoid mycorrhizal fungi (ErMF) and organic matter influenced the establishment of dwarf ericoid species that characterize NW European Atlantic lowland heaths. Neither intervention had any positive effect on ericoid establishment in field or greenhouse conditions. In the greenhouse experiment, organic matter (from commercial refuse) increased heather (Calluna vulgaris) cuttings mortality, although surviving plants showed enhanced shoot growth when ErMF were added. All field plots were dominated by combinations of grasses, gorse (Ulex europaeus), and bare ground. Establishment of ericaceous plants was remarkably low (<4%) after 3 years and Erica tetralix and C. vulgaris abundance in organic matter (which increased pH) or ErMF treatments was reduced compared to untreated control. Although our experiments suggest that research on soil manipulation treatments is required to elucidate the conditions necessary for heathland establishment, corroboration of our greenhouse trial results in field conditions highlights the value of the former in informing the latter. We identify low pH, high lignin (e.g. pine) litter as one potentially worthwhile soil amelioration treatment and suggest how the use of naturally colonized/preinoculated “nursemaid” plants could facilitate heathland restoration.