Role of Buried Viable Seeds in the Recolonization of Disturbed Ground by Heather (Calluna Vulgaris [L.] Hull) In the Cairngorm Mountains, Scotland, U.K.

Abstract

Heather (Calluna vulgaris [L.] Hull), an evergreen dwarf shrub, is the predominant species on great tracts of Scottish moorland over a wide altitudinal range. It flowers annually but seed production is variable and declines substantially with increasing altitude. Heather seeds can, however, accumulate in the soil in huge numbers, up to nearly 100,000 seeds m^–2. Seed longevity is much greater at high altitude than it is at lower altitude, so the densities of buried germinable seeds do not decrease as steeply with increasing altitude as do the densities of the seeds shed annually. Above the forest limit buried seeds become the more important, and in some years the only, source of heather propagules for colonizing disturbed ground. Initial establishment from buried seeds is generally successful but first winter mortality can be particularly severe at high altitude. The store of buried seeds may help to remedy these losses.

Buried seeds probably contribute to heather's dominance of vegetation over a wide range of environmental conditions and its persistence in marginal habitats. A reservoir of buried viable seeds may take many years to accumulate, especially at high altitude. It is a valuable resource which is liable to destruction by human disturbance of mountain vegetation.