Formalized classification of European fen vegetation at the alliance level

Abstract

Aims Phytosociological classification of fen vegetation (Scheuchzerio palustris‐Caricetea fuscae class) differs among European countries. Here we propose a unified vegetation classification of European fens at the alliance level, provide unequivocal assignment rules for individual vegetation plots, identify diagnostic species of fen alliances, and map their distribution. Location Europe, western Siberia and SE Greenland. Methods 29 049 vegetation‐plot records of fens were selected from databases using a list of specialist fen species. Formal definitions of alliances were created using the presence, absence and abundance of Cocktail‐based species groups and indicator species. DCA visualized the similarities among the alliances in an ordination space. The ISOPAM classification algorithm was applied to regional subsets with homogeneous plot size to check whether the classification based on formal definitions matches the results of unsupervised classifications. Results The following alliances were defined: Caricion viridulo‐trinervis (sub‐halophytic Atlantic dune‐slack fens), Caricion davallianae (temperate calcareous fens), Caricion atrofusco‐saxatilis (arcto‐alpine calcareous fens), Stygio‐Caricion limosae (boreal topogenic brown‐moss fens), Sphagno warnstorfii‐Tomentypnion nitentis (Sphagnum‐brown‐moss rich fens), Saxifrago‐Tomentypnion (continental to boreo‐continental nitrogen‐limited brown‐moss rich fens), Narthecion scardici (alpine fens with Balkan endemics), Caricion stantis (arctic brown‐moss rich fens), Anagallido tenellae‐Juncion bulbosi (Ibero‐Atlantic moderately rich fens), Drepanocladion exannulati (arcto‐boreal‐alpine non‐calcareous fens), Caricion fuscae (temperate moderately rich fens), Sphagno‐Caricion canescentis (poor fens) and Scheuchzerion palustris (dystrophic hollows). The main variation in the species composition of European fens reflected site chemistry (pH, mineral richness) and sorted the plots from calcareous and extremely rich fens, through rich and moderately rich fens, to poor fens and dystrophic hollows. ISOPAM classified regional subsets according to this gradient, supporting the ecological meaningfulness of this classification concept on both the regional and continental scale. Geographic/macroclimatic variation was reflected in the second most important gradient. Conclusions The pan‐European classification of fen vegetation was proposed and supported by the data for the first time. Formal definitions developed here allow consistent and unequivocal assignment of individual vegetation plots to fen alliances at the continental scale.

Modelling the distribution and compositional variation of plant communities at the continental scale

“…The second dataset consists of 1,510 vegetation plots (Figure ) sampled in areas from 1 to 100 m 2 assigned to mountain base‐rich fens (hereafter, rich fens) in a pan‐European classification (Jiménez‐Alfaro et al., ). This study found this range of plot sizes appropriate for describing the alliance Caricion davallianae (Peterka et al., ), which is mainly associated with base‐rich and waterlogged soils in cool areas with high precipitation (Essl, Dullinger, Moser, Rabitsch, & Kleinbauer, ; Jiménez‐Alfaro et al., ). This vegetation characterizes the European protected habitat “7230 Alkaline fens” and the EUNIS type “D4.1—Rich fens, including eutrophic tall‐herb fens and calcareous flushes and soaks” (Šefferová Stanová, Seffer, & Janák, ).…”

Classification of the European marsh vegetation (Phragmito‐Magnocaricetea) to the association level

“…This work is another contribution towards the construction of the formalized classification system of European vegetation, complementing the series of recent studies focusing on the diversity of selected vegetation types across the whole of Europe (Douda et al, ; Peterka et al, ; Willner et al, ; Marcenò et al, ). At the same time, we hope it can also become a step towards the construction of a supra‐continental classification of wetlands.…”

“…The threshold values of percentage cover in the formulas were assigned arbitrarily following our personal experience and consistently with similar classifications developed in the past (Chytrý, ; Landucci, Tichý, et al, ; Peterka et al, ). Assignment rules based on the overall physiognomy of the vegetation stands ▫︎If the total cover of the group ‘shrubs and trees’ (group N.C) is >25% or that of ‘other herbaceous plants and dwarf shrubs’ (N.B) is >50%, the plot does not belong to marsh vegetation of the Phragmito‐Magnocaricetea class, irrespective of the cover value of marsh species (included in the group N.A). ▫︎If the previous point is not true and the total cover of ‘competitive marsh forbs’ (N.A.3) is >25%, the plot is assigned to an association defined by species belonging to this group, irrespective of the cover value of other marsh species (included in N.A.1, N.A.2). ▫︎If the previous point is not true and the total cover of ‘emergent reedlike plants and bulrushes’ (N.A.2.1) and ‘marsh sedges’ (N.A.2.2) is >25%, the plot is assigned to an association defined by species belonging to these groups irrespective of the cover value of other marsh forbs (included in N.A.1). ▫︎If the previous point is not true and the total cover of ‘amphibian plant species’ (N.A.1.1) and ‘less competitive marsh forbs’ (N.A.1.2) is >25%, the plot is assigned to an association defined by species belonging to these groups. Assignment rules based on species dominance (valid if at least one of the assignment rules according to the overall physiognomy is met) ▫︎If no species in a marsh vegetation plot has a cover ≥25%, the plot is assigned to the association characterized by the species that dominates the vegetation in the plot (the species with the highest cover value in the plot). ▫︎If the cover of a particular ‘marsh plant species’ (any species included in N.A) is >25%, the plot is assigned to the association characterized by that species. ▫︎If two or more species have identical cover values, the assignment of the plot is based on the priority degrees.…”

“…Cocktail and similar methods involving classification expert systems have previously been applied mainly at the national level (Šilc & Čarni, 2007;Chytrý, 2007Janišová et al, 2007;Kącki, Czarniecka, & Swacha, 2013;Li et al, 2013;Rodríguez-Rojo, Fernández-González, Tichý, & Chytrý, 2014), but recent applications were developed also at the continental scale for European floodplain forests (Douda et al, 2016), beech forests (Willner et al, 2017), fens (Peterka et al, 2017), and coastal dune vegetation (Marcenò et al, 2018). The original Cocktail approach made it possible to formalize vegetation classification using the rules of formal logic, combining sociological species groups through the operators and, or and not (Bruelheide, 1997).…”

The ratio between bryophyte functional groups impacts vascular plants in rich fens

“…In our study, this group of species is represented especially by Primula farinosa (Hájek et al., ; Theodoridis et al., ) and Saxifraga hirculus (Dítě et al., ). The effects of relictualism and the type of nature limitation might multiply in Saxifraga hirculus , the species with the greatest effect of latent variables that shows affinity to both the relict sites (Hájek et al., ; Dítě et al., ) and the N‐ instead of P‐limited sites (the Saxifrago‐Tomentypnion alliance, Peterka et al., ).…”