Regional and Vegetation-Ecological Patterns in Northern Boreal Flark Fens of Finnish Lapland: Analysis from a Classic Material

Abstract

SUMMARYPatches of intermediate fen, dominated by Molinia caerulea, Trichophorum cespitosum and Loeskypnum badium and resembling low aapa mire strings (lawn strings), were found on a sloping rock outcrop near the summit of Koitelainen Hill, central Finnish Lapland. Using eighteen 56-cm diameter plots and NMSordination we compared the vegetation of the patches to that of (A) corresponding larger fens belonging to a well-known north-Finnish mire site type Loeskypnum badium fen, (B) to that of narrow seepage soaks dominated by Warnstorfia sarmentosa, and (C) to that of a local heath patch. Ordination of the sample plots suggested a 'horizontal gradient' (general wetness) and three 'vertical gradients' (1: stability of the water regime; 2: poor-rich species; 3: frost action). Species richness increased along both the horizontal and the vertical gradient, from wet seepage areas to drier Loeskypnum badium fens, to intermediate fen patches and finally to the heterogeneous heath patch. We regard the fen patches of Koitelainen as belonging to an ecologically extreme group, the water-fluctuating lawn-fens. The water-fluctuating lawn-fens are characterised by a thin peat layer with high humification degree, caused by intermittent aeration during drought periods, as well as by the specific community composition, which is evidently partly structured by the seasonal drought tolerances of individual fen species.

Gradients, Species Richness and Communities in Eastern Finnish Sloping Fens

“…In the eastern Finnish sloping fens, species richness was positively related to the poor-rich and mire-expanse-to-margin gradient, and negatively to mire surface level. In other words, an increase in wetness resulted in a decrease in species richness, as was also found by Laitinen et al (2017) for northern Finnish boreal wetland habitats, and by Hájek et al (2005) for subalpine fens in the Vitosha Mountains, Bulgaria. Additionally, species richness was negatively related to stable-to-unstable water-regime gradient (water regime instability decreased species richness).…”

“…8). Northerly location of flark fens is associated with Finnish aapa mires, and with the effect of spring floods from melting of snow in those areas (Ruuhijärvi 1960, Laitinen et al 2017. Additionally in sloping fens, poor fens tended to be less common towards the south (Fig.…”

“…Results obtained at the regional level often serve as references and are used to validate those from continental-scale studies developing classifications and surveying of larger-scale distribution patterns of vegetation types. To date, however, studies on the links between environmental gradients and mire vegetation types recognized in different parts of Europe are few (see Laitinen et al 2017).…”