Heathland Restoration after Mineral Extraction

Abstract

Restoration Ecology has been developed over the last 40 years in efforts to better understand how to restore, recreate or reclaim land damaged by human activities. Lowland heath is one of the more difficult habitats to recreate due to the complicated interactions of soil chemistry and plant physiology and structure. This study investigated the ecological restoration of heathlands at a china clay mineral extraction site in the UK. Assessment of historical restoration practices revealed that previous work carried out on the study site is not achieving Atlantic Lowland Heath (ALH) and that specific amendments might be necessary. Consequently, work carried out in the greenhouse assessed the effectiveness of commercial Ericoid Mycorrhizal Fungi (ErM, Rhodovit) and organic matter (compost) on the growth of Calluna vulgaris. The highest survival of plants was observed in the stored topsoil, followed by stored topsoil with commercial ErM. DNA analysis confirmed the presence of ErM fungi in the order Heliotales on root hairs of plants grown in the ErM treated soil. Chemical analyses of topsoil stored in soil berms for up to five years identified some changes, in particular, downward movement of some chemical elements. While the soil remained suitable for restoration use after prolonged storage, the results indicated that amendments to achieve a higher soil C:N ratio may improve ALH establishment. Using methods developed from analysis of historical restorations, a large-scale field trial evaluated the effect on successful heathland restoration of adding plant accessible nutrients, organic material or ErM, as well as combinations of these treatments. The results showed that the addition of seeds to stored topsoil resulted in the highest number of C. vulgaris plants germinating in the final field season. Unfortunately, none of the treatments successfully created ALH within three field seasons. The conclusions reached from field trials and detailed analyses of stored topsoil point towards the importance of adding organic matter that specifically elevates the C:N ratio of the substrate to be restored. This merits further investigation. Overall, this work supports the work and the findings of previous studies detailing that the successful establishment of ALH is a complex undertaking, requiring minimal intervention with controlled nutrient addition.