Ecological and soil development of 19th Century iron and coal mine wastes at Bryn Defaid, South Wales

Abstract

Prior to modern regulatory control, mine wastes were typically abandoned and left with minimal disturbance or improvement at the former mine site. Bryn Defaid is one such example and is located on the western slopes of Aberdare Mountain, Rhondda Cynon Taff, Wales, where spoil materials from iron and coal mining were deposited from the mid-1800s. In this study, we investigated the relationship between varied extents of floristic development (including mosses, heather, acidophil grasses and diverse communities of lichens), and the development of incipient soils after 150 years of pedogenesis. We hypothesised that observable categorical changes in the floristic development would be reflected in differential soil development and in its associated microbiota. Ecological development was classified into six floristically defined categories: Bare ground, Primary colonisation, Lichen dominant, Moss-lichen mix, Moss-vascular plant mix and Moss heather mix. Soil chemistry showed no significant effect of floristic development on pH (ca.4.5–5.0) and basic cations but a significant effect on soil organic matter and total nitrogen and phosphorus. These higher concentrations were typically found in the moss dominated sites. Soil microbial biomass was also high under mosses, particularly the moss-heather community. Abiotic and biotic conditions under lichen communities were not significantly different to those under later floristic communities, suggesting that other factors (potentially spoil stability) are affecting the development of lichen communities. Overall, there was a relationship between some key soil properties and the extent and stage of floristic development. We conclude that plant-soil feedbacks may play an important role in controlling the development of post-mining plant ecology and related pedogenesis.