Vegetation transition following drainage in a high-latitude hyper-oceanic ecosystem

Abstract
Questions: How does draining affect the composition of vegetation? Are certain functional groups
favoured? Can soil parameters explain these differences?
Location: Central Faroe Islands, treeless islands in
the northern boreal vegetation zone. Since 1987, an
area of 21 km2 at 100–200 m a.s.l. was drained in
order to provide water for hydro-electric production.
Method: Vegetation and soil of a drained area and a
control, undrained neighbouring area of approximately the same size were sampled in 2007. Six sites
were sampled in each area. The vegetation was
classified with cluster analysis.
Results: Four plant communities were defined in the
area: Calluna vulgaris–Empetrum nigrum–Vaccinium
myrtillus heath, Scirpus cespitosus–Eriophorum angustifolium blanket mire, Carex bigelowii–
Racomitrium lanuginosum moss-heath, Narthecium
ossifragum–Carex panacea mire. Heath was more
extensively distributed within, and was the dominant community of the drained area, whereas mossheath was more extensive in the undrained area.
Blanket mire and mire had approximately the same
distribution in both areas. For the blanket mire,
species composition indicated drier conditions in the
drained than in the undrained area. The drained
area had higher frequencies of woody species and
lichens, grasses had finer roots and available soil
phosphate was considerably higher, whereas the
undrained area had higher frequencies of grasses
and sedges.
Conclusion: The dominant plant communities were
different in the two areas, which indicated that the
blanket mire was drying in the drained area. Higher
concentration of soil phosphate in the drained area
also indicated increased decomposition of organic
soils owing to desiccation.
Keywords: Drainage; Fine roots; Functional groups;
Plant communities; Soil decomposition