HEATHLAND SEEDBANKS UNDER BRACKEN PTERIDIUM-AQUILINUM (L) KUHN AND THEIR IMPORTANCE FOR RE-VEGETATION AFTER BRACKEN CONTROL

In Great Britain, the regeneration of heathland and moorland plant com munities after bracken control is slow and variable. Successful restor ation depends on the availability of seed and the provision of suitabl e regeneration niches, as well as on the expansion of the plants previ ously present underneath the bracken canopy. This study investigates t he availability of the seed resource of heathland species and its dist ribution, both in relation to increasing time since bracken invasion a nd with respect to its presence in litter or mineral soil. Calluna vul garis was found to be the predominant species that germinated from the soil and litter beneath bracken at the sites studied. It appeared in greatest numbers from samples taken outside and at the edge of the bra cken patch; numbers decreased deeper into the patch. Land which has be en under bracken for a considerable period (>50 years) is likely to ha ve a very reduced seedbank so that some form of propagule introduction , as well as litter disturbance, may be needed to speed up regeneratio n. On sites which have been invaded by bracken more recently, it is li kely that litter incorporation into the soil would conserve the seed r esource, whereas burning or litter removal would remove a significant proportion of that seed resource. (C) 1996 Academic Press Limited