Bogs (moors and fens)

In the context of bogs two important distinctions must be made: the intermediate and high moors on the one hand and the fens and wet meadows on the other.

Moors are only represented in areas with high rainfall and/or reduced evaporation, for instance as in north-west Germany, north-west and especially northern Europe in general, in the northern foothills of the Alps or some mountain ranges. They are supplied purely by rainfall and are (were) therefore very nutrient-poor and low in minerals (acid). They grow in height as the peat moss (Sphagnum sp.) that especially is forming the moors, dies at its bottom and grows apically in the height. Thus the moor loses the contact with the mineral soil and a ombrogene rain moor has formed (typically higher in the center, curvature). Bogs are generally species-and flower-poor. But their biocoenosis is highly specialized and unique. Some of the butterflies are also found in the siliceous dwarf shrub belts of the Central Alps (for instance Colias palaeno), where Ericaceae are richly represented as it is the case in the bogs. Intact raised bogs (undisturbed water resources!) have almost vanished in Central Europe, but there are still more or less disturbed bogs left. They are threatened by the following factors:
  • Peat extraction for garden peat, beauty industry and fuel (the latter today probably only in Eastern Europe)
  • Drainage and subsequent succession over heath moors to birch / pine forests or intensification (maize agriculture etc.)
  • Fragmentation by roads
  • Spruce afforestation or intensification of flower-rich wet meadows in the border area (loss of nectar habitat)
  • Nutrient deposition from the air and adjacent areas
Some pictures (please click for enlargement):
Moor in the foothills of the Alps moor in the German Prealps partially dewatered moor in progressed heath and shrub stage Sphagnum and Oxycoccus: typical habitat in the bog Moor in the Bavarian foreland of the northern Alps

Fens owe their existence not only rainfall, they get at least parts of their water from below. They arise in the siltation areas of lakes (siltation fens, in rainy areas a precursor of raised moors), on impermeable layers such as in basins, in the catchment areas of rivers or in the exit area of ??sources. Richest in species are base-rich forms such as the calcareous fen (Caricion davallianae) with the eponymous sedge or base richer forms of Molinietum (Molinia meadows). Fens, especially wet litter meadows are often caused by deforestation of swamp forests and subsequent mowing. This mowing traditionally took place late in September and October and served the litter supply for the stables in times before slatted floors with liquid manure came in fashion. Due to the late, extensive mowing and mostly low to complete lack of fertilization also late-flowering plants could develop and a felting was prevented. In addition, usually a high structural diversity of herbaceous forb communities on the edges, ditches, embankments and woody ledgers, so that quite a high number of species of butterflies are able to reproduce with success. If litter meadows are not mowed, they are substituted by forb or reed communities in the long term. Depending on the area character willows, birch or alder penetrate and the development of swamp forest begins. Fens are threatened by the following factors:
  • Fertilization and conversion to intensive meadows or corn fields
  • Afforestation
  • Abandonment of mowing and subsequent succession
  • Overbuilding
Besides real fens also once to twice cutted wetlands are of importance, such as cabbage thistle (Cirsium oleraceum) meadows or Sanguisorba officinalis-meadows. Typical species are Maculinea teleius, Lycaena hippothoe or Adscita statices. Such meadows are, however, almost extinct except for a few remaining locations mostly in river valleys.

Some pictures:
fen in May fen in summer fen, tending to intermediate moor Calcareous fen in the northern foreland of the Alps near Memmingen (Germany) Calcareous fen on the eastern Swabian Alb (Germany) near Dischingen Small fen with Zygaena trifolii, Brenthis ino, Maculinea teleius, Maculinea nausithous etc. in northern Württemberg (Germany) Swampy area with Carex, Scirpus and much Typha on the eastern Swabian Alb (Germany)

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