Sedge-moss vegetation of fens, transitional mires and bog hollows in the temperate, boreal and Arctic zones of the Northern Hemisphere
Scheuchzerio palustris-Caricetea fuscae Tx. 1937
Scheuchzerio palustris-Caricetea fuscae Tx. 1937
sch01 | There are two contrasting (as well as some transitional) approaches to the classification of fens in Europe: (1) The first one is delimiting associations and alliances using dominance of fen plant species with rather wide niches (e.g. Dierßen 1982); (2) the other approach relies on species groups and follows ecological classification into extremely rich fens, rich fens, moderately-rich fens, poor fens, and dystrophic bog hollows (for details see Hájek et al. 2006). The most substantial difference with crucial consequences for nomenclature is that the former approach merges bog hollows with different types of minerotrophic fens dominated by either Rhynchospora alba or Carex limosa into a single alliance − the Rhynchosporion albae Koch 1926. Many vegetation survey accounts keep only the bog hollows in this alliance, that is however, not consistent with the nomenclatural type of the Rhynchosporion albae. The other surveys prefer to discern the floristically contrasting minerotrophic fens and ombrotrophic bogs. The second substantial difference is that the former approach involves all mires dominated by Carex lasiocarpa, C. diandra and/or C. chordorrhiza into a single alliance − the Caricion lasiocarpae regardless of variations in total species composition (including bryophytes) controlled by variable base saturation underpinning the principal floristic gradient within the mires. The latter approach divides the principal base-saturation gradient into particular sections that correspond to alliances, with the above-mentioned species occurring in more alliances. These two approaches are so different that the application of nomenclatural rules becomes inherently context-dependent. (M. Hájek).