Chronosequence of former kaolinite open cast mines suggests active intervention is required for the restoration of Atlantic heathland

Abstract

Atlantic lowland heath (ALH) is a priority conservation habitat in Western Europe, but restoration efforts have met with mixed success due to the complexity associated with replicating establishment conditions. By virtue of their impoverished, often acidic soils and geographic location in areas naturally occupied by ALH communities, former kaolinite mine sites may offer an excellent opportunity for heathland restoration. Using a chronosequence of former open cast kaolinite mines in South West England (0, 2, 27, and 150 years since mining ceased), we determined the ability of ALH vegetation and soils to reestablish naturally and in addition, for the three youngest sites, how the reinstatement of stored overburden affected heathland regeneration. Analysis of soil characteristics revealed major differences in the levels of acidity, organic content, and fertility between abandoned kaolinite sites and a nearby natural reference heath. Even 150 years after mining ceased, concentrations of all major soil nutrients and organic content were lower, and pH higher, than undisturbed ALH. The reinstatement of overburden did little to improve soil quality, since all former kaolinite sites were dominated by mesotrophic grasses, rather than species characteristic of the target ALH community. We conclude that to maximize the potential of former open cast kaolinite sites for ALH reestablishment, changes in pre- and postrestoration management are required. These include modification of how overburden is stockpiled, while the addition of organic material, microbial communities, and sulfur (to reduce soil pH) to reinstated overburden are likely also essential interventions to facilitate successful ALH establishment.