Effectiveness of Calluna-heathland restoration methods after invasive plant control

Abstract

Restoring natural communities after invasive plant control is one of the fundamental challenges of ecological restoration. Despite advances in invasive control methods, restoration failures caused by a lack of native community re-establishment are common. This is especially frequent in the upland heathlands of Great Britain invaded by Pteridium aquilinum. As a consequence, active revegetation methods are needed to increase the performance of native plant species. Here, we assessed the effectiveness of Calluna-heathland vegetation restoration treatments on the developing plant community composition in combination with a set of recommended Pteridium-control methods applied at the local scale. Four stand-alone replicated experiments were set up in two regions of Great Britain. The experiments had a similar randomized block split- or split–split-plot design with six Pteridium-control treatments applied randomly to the main-plots (10m×40m); and Calluna-heathland vegetation site-specific restoration treatments applied to sub- and sub-sub-plots. The restoration treatments included stock-poof fencing, fertilizing, harrowing, seeding and prescribed litter-burning. The results showed that the effectiveness of site-specific Calluna-heathland restoration methods applied in conjunction with Pteridium-control methods was very low. Only sheep grazing and prescribed Pteridium-litter burning favoured the restoration of Calluna-heathland community composition. In contrast, fencing, fertilizing and harrowing were ineffective. Surprisingly, Calluna seeding only showed short-term positive effects when applied with asulam spray treatments. Considering the costs and benefits of the restoration measures studied as part of this integrated Pteridium-control/heathland restoration programme, the most successful methods were sheep grazing and prescribed Pteridium-litter burning; both are traditional methods of heathland management. It seems that effective restoration actions should initiate gradual change that aims to create a continuous transition to a more desirable conservation value state.