Habitat qualities versus long-term continuity as determinants of biodiversity in boreal old-growth swamp forests

Natural swamp forests are extremely rare in Sweden because of extensive drainage and logging activities. This study reports a total of 517 species (148 vascular plants, 131 mosses, 64 hepatics, 142 lichens and 32 wood-inhabiting fungi) from 10 small remnants of boreal old-growth swamp forests. The 195 bryophytes found represent 33% of the total number of bryophyte species in the Swedish boreal flora. As the average area of the forests was only 2 ha, this figure clearly illustrates the important role of the swamp forests as centres of bryophyte biodiversity. There was no relationship between the occurrence of 33 lichen and fungi species considered to indicate natural forests with long stand continuity and the known long-term continuity of the forests. The forests most affected by earlier natural and man-made fires harboured more of these species than forests less affected by fire disturbance. The most important variable explaining biodiversity as well as presence of 'continuity indicator species' was the amount of dead wood present. A more critical and careful use of the concept of forest continuity is needed. (C) 1997 Elsevier Science Ltd.