The influence of terrain age on the species composition of alpine "climax" heath communities in southern Norway
Abstract
This paper assesses the relationship of terrain age to vegetation diversity and the frequency of individual species, in low- and mid-alpine plant communities. In Jotunheimen. southern Norway. It focuses on changes in the composition of vegetation at the boundaries of 15 glacier forelands (where sharp disconunuities exist in terrain age from 250 years to c. 9,000 years) to determine whether the vegetation on the terminal moraine has yet reached a "climax" state. Statistically significant differences exist in the frequency of several taxa at the glacier foreland boundary: Vaccinium vitis-idaea. Vaccinium spp. Encales. Carex spp., Cyperaceae/Juncaceae. Festuca ovina and Gramineae. Diversity indices indicate higher diversity and lower dominance outside the foreland boundary. The length of time available for succession is considered the primary reason for the discontinuity in vegetation. Alternative hypotheses relating to the influence of local-scale differences in biotic and abiotic factors are considered. Variations in the substrate, historical events and grazing pressure probably contribute to differences in species composition. It is inferred that succession is still proceeding on the terminal moraine, that vegetation within the terminal moraine has not reached equi- librium with its environment, and that it has not achieved a "climax" state.
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