Re-establishment of Calluna vulgaris (L.) Hull in an eight-year grazing experiment on upland acid grassland

Upland heathland is an internationally important habitat but a large area in the UK has been degraded to acid grassland by intensive livestock grazing. Re-establishment of dwarf shrubs, particularly Calluna vulgaris (L.) Hull, is a key objective for restoring heathland on these sites. A replicated plot-scale experiment was set up to examine effects of disturbance and seed addition on C. vulgaris establishment in a Nardus stricta L. grassland under three grazing regimes: sheep only (1.5 ewes ha−1 for 10 months per year); cattle only (0.5 heifers ha−1 in summer only); and, the cattle regime combined with sheep (1.0 ewes ha−1 for 10 months per year). Early results of the experiment have been reported previously but it was not known if these results were an indication of the longer-term restoration success. Here we evaluate the success of the restoration methods (disturbance, seeding treatments and grazing regime) eight years after the treatments began. In seeded plots, young C. vulgaris plants had greatest above-ground height, dry weight and shoot length if grazing was excluded or the cattle-only regime was applied. C. vulgaris cover was greatest, and increased most, in plots that had been disturbed, seeded and ungrazed or subjected to the cattle-only regime. The vegetation in these plots also became more similar to reference sites with 50% or more cover of C. vulgaris. The invasive Juncus effusus L. was more frequent in disturbed and grazed plots but less frequent in plots with C. vulgaris established from added seed. Previous results that showed the benefits of disturbance and seeding treatments were still valid but changes in the vegetation composition were still occurring and longer-term studies will be needed to determine when grazing regimes including sheep might be reintroduced.