The significance of the dormant viable seed bank in the restoration of heathlands

Abstract

The dormant viable seed bank of heathland dwarf shrub species was investigated in several different heather moorland soils. Soil was incubated in a warm, moist environment for periods of up to twelve months. Generally there was a high density of viable seeds of Calluna vulgaris, Erica cinerea and Erica tetralix and several other heathland species. At all sites, a substantial portion of the seed bank (usually more than 90%) of all the species occurred in the upper 40 mm of the soil. This upper soil layer also contains a ‘bud bank’ of certain species (e.g. Molinia caerulea and Vaccinium myrtillus), which is equally important for subsequent regeneration of these species. When heathland is disturbed by mineral extraction, construction operations and installation of pipelines, it is essential that the seed-rich topsoil is carefully conserved to enable subsequent restoration to be successfully achieved. Since the seed bank is concentrated in a relatively shallow upper soil layer, it is important that only the upper 40–50 mm is removed. A greater depth of soil removal only dilutes the seed bank and reduces the usefulness of the separately stripped topsoil as a source of plant propagules.