A study of the restoration of heathland on successional sites: changes in vegetation and soil chemical properties.
Abstract
Lowland heaths are high-profile ecosystems for conservation action in the UK, but many areas have been invaded by Betula spp., Pinus sylvestris, Pteridium aquilinum and Rhododendron ponticum. As succession occurs on heaths, changes occur in both the vegetation and the soil chemical properties of the site. Nine heathland sites in the Poole Basin area of Dorset were studied, where management of successional sites to restore heathland had occurred. The efficacy of heathland restoration in terms of both the vegetation and soil chemical properties was assessed. The management enabled many heathland species to establish and the majority of sites to start to become similar to the neighbouring heathland. The reversion of increased soil nutrients was found to be more problematic, with levels of ammonium-nitrogen, phosphorus, pH, calcium and magnesium remaining greater than those of the heathland soils. The vegetation and soil data were analysed using CANOCO (canonical correspondence analysis) and were then used to test four hypothetical models that related changes in biotic factors (vegetation) and abiotic variables (soil nutrients) following management to the success of the restoration of heathland on successional sites. A second CANOCO analysis was carried out in which the managed sites were treated as passive samples. This model was used to measure the distances between the heath, successional and managed sites. These distances provided measures of management success and the resilience of the treated late-successional ecosystem. The successional species present before management affected the success of reversion. Management of Pinus sylvestris sites was generally more successful than management of other sites, especially those invaded by Betula spp. The most effective management technique was litter-stripping, especially if bare mineral soil was exposed, which reduced the nutrients available and improved and accelerated the success of reversion.