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.

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

“…(3) “Metals”: Cations were added at the following amounts per plot; sodium 123 g (13.50 mg/kg), calcium 111 g (12.5 mg/kg), potassium 324 g (35.40 mg/kg), and magnesium 449 g (49.03 mg/kg). These amounts were based on Lane et al (2019) to increase observed levels in stored overburden to heathland soil concentrations reported by Clarke (1997). Applied in pellet form (Thompson and Morgan, Suffolk, U.K.), the cations were mixed and broadcast by hand to ensure an even spread.…”

“…Despite the ability of many heathland species to cope with a stressful edaphic environment, the removal and storage of overburden, later used for mine rehabilitation, often reduces nutrient concentrations to levels well below those naturally found in heathland soils and insufficient for plant establishment and growth (Coppin & Bradshaw 1982; Clarke 1993, 1997; Lane et al 2019). Overburden storage can also raise pH to levels unsuitable for heathland establishment, and encourage instead recruitment of competitive grass species that limit ericaceous plant establishment (Marrs et al 1998; Green et al 2015; Lane et al 2019). Moreover, reinstatement of a carbon and nutrient‐limited, highly porous mineral overburden inevitably limits heathland establishment (Diaz et al 2006; Smith & Read 2010; Machado et al 2013; Bateman et al 2016).…”

“…Studies such as Lane et al (2019) underscore the need for active soil management as a basis to facilitate successful (heathland) restoration (see also Holmes 2001: Benigno et al 2013; Clemente et al 2016; Glen et al 2017). These interventions include the addition of organic matter (OM) to increase nutrient levels, retain moisture, and stimulate soil biota (Smith & Read 2010; Muñoz‐Rojas et al 2016; Ngugi et al 2018).…”

Enhancing biodiversity and ecosystem services in quarry restoration – challenges, strategies, and practice

“…As an example, Lane et al () and collaborators found that mesotrophic grasses dominated former kaolinite mining sites, instead of typical lowland heath species. Such differences in vegetation composition were attributed to soil characteristics, which revealed lower acidity levels and organic content.…”

Evaluating Heathland Restoration Belowground Using Different Quality Indices of Soil Chemical and Biological Properties

“…Some studies have shown that only the presence of both above-(vegetation) and belowground (microbiota and fauna) heathland species leads to a fast assembly toward the target ecosystem [81,83]. Therefore, in terms of assessing the efficacy of application of elemental sulphur to acidify pasture, sole reliance on chemical indicators to quantify the success of a restoration may lead to misleading conclusions.…”