Primary Succession of Plant Assemblages on a Glacier Foreland-Bodalsbreen, Southern Norway

Vetaas, Ole

Primary successions on glacier forelands have been widely described as changes of plant assemblages, although many studies show that the assemblages may be more apparent than real. Some doubt has also been cast on the occurrence of successional convergence on deglaciated terrain. Vegetation data from five dated terminal moraines in southern Norway, created between 1750 and 1930, were classified by TWINSPAN. The distinctness of the TWINSPAN groups and their relation to the spatial and temporal gradients were analysed by Canonical Correspondence Analysis. The successional sequence can be described as a physiognomic development; from cryptogam-mats, to a heath-phase, which may then be over-grown by Betula shrubs that develop into a sub-alpine Betula pubescens forest. Most species (79%) in the Racomitrium canescens and Stereocaulon assemblage on the youngest moraine are also found in the Betula pubescens forest on the oldest moraine. However, the establishment of some species seems to be facilitated by other species. The floristic difference between the TWINSPAN groups decreases with time suggesting that successional convergence has occurred. The spatial micro-variation is reduced once a close canopy of Betula is established on the oldest moraine, but there are clear variations related to moraine positions on the other moraines.

Primary Succession of Plant Assemblages on a Glacier Foreland-Bodalsbreen, Southern Norway

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