Methods: In 2009, we resurveyed three plant sociological studies up to 85 years after the first surveys.
Vegetation data were recorded from 1m2 non-permanently marked plots, and soil pH was measured.
We applied restricted permutation tests to evaluate whether observed changes in vegetation (species
richness, occurrence frequency, coverage) and in soil pH were significant and independent of plant
community type. We compared species co-occurrences over time to study changes in species
composition and to identify the species most likely causing these changes.
Results: Total number of species and average number of species per plot has not changed and are 75
and 9, respectively. Occurrence frequency changed significantly for 34% of the 64 species tested (11
species increased, 11 decreased). Species cover decreased significantly for 27% of the species and
increased for one species. Observed changes in frequency and cover are not significantly related with
species’ functional groups or species affiliated with moist or dry habitats. Polygonum viviparum,
Saxifraga cernua and Alopecurus borealis have changed most in co-occurring with other species. Soil
pH increased significantly from 6.4 to 6.8.
Conclusions: Our results suggest that the strong climatic warming in the High Arctic over the past
decades has contributed to significant changes in the vegetation studied on Svalbard over the past 85
years. Internal community re-structuring and the overall stability in species richness may be explained
by time-delayed responses of well-established communities, and/or by a limited size of the species
pool in the area.
