INFLUENCE OF BRYOPHYTES AND MICRORELIEF CONDITIONS ON PICEA-ABIES SEED REGENERATION PATTERNS IN BOREAL OLD-GROWTH SWAMP FORESTS

The occurrence of naturally regenerated Picea abies (L.) Karst. emerge nt seedlings (i.e., ii year old) and established seedlings (>1 year ol d and up to 1.3 m in height) was monitored in relation to the occurren ce of microrelief conditions in 10 old-growth swamp forests in norther n Sweden. Further, nine different microhabitat types were defined in r elation to the microrelief and bryophyte species present, and for five of the forest sites, a 4-year sowing experiment was performed by plac ing P. abies seeds in each microhabitat type. Although logs, roots, an d stumps only occupied 14% of the forest floor, 43% of P. abies regene ration occurred in these microrelief conditions. Hummocks occupied 35% of the forest floor and harboured 48% of the regeneration, while holl ows and flat ground occupied 49% of the forest floor but included only 9% of the regeneration. Seedling emergence from sown seeds was highes t in the Sphagnum spp. microhabitats and lowest in the Hylocomium sple ndens (Hedw.) and Pleurozium schreberi (Brid.) microhabitats. Seedling establishment was highest in the presence of Sphagnum spp. and Pleuro zium growing on logs. Seedling mortality was mainly caused by smotheri ng by bryophytes. Elevated microhabitats are thus crucial for P. abies regeneration and should consequently be considered in the management of boreal swamp forests.