The above mentioned fens are fed by nutrientcontaining water from streams, springs and groundwater. When peat accumulation leads to a raising of the surface to a height where groundwater is no longer accessible to plants growing in the fen, the water supply is limited to that supplied by rainfall and, consequently, nutrient supply diminishes, resulting in acidification in the peat body. The number of plant species declines and only several specialists remain. The appearance of typical Peat Mosses (such as Sphagnum magellanicum and S. rubellum) indicates the start of a development to a raised bog. The prerequisite for this is sufficient equally distributed rainfall. Figure 8.8 shows an artificially created raised bog. Sphagnum mosses have special cells (Hyalocytes) that are able to exchange cations for hydrogen (H+). This causes further acidification. Sphagnum mosses form a layer covering the whole bog-surface and grow constantly upward whilst their lower parts die and, at the very low rates of decomposition under such acid conditions, they thereby form bog peat. Figure 8.11 shows a section through an idealised type of a siltedup lake in the northern alpine foothills of Central Europe with carr, fen and straw meadow, such as a convex bent raised bog. The wet centre accommodates typical bog flora, such as Harestail Cotton Grass (Eriophorum vaginatum) or
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8.8
Artificial raised-bog planting at Erich Maier, Altenberge, Germany. The water level is maintained by the use of storage containers, hidden in the peat substrate. Besides central European plants spectacular North American insectivorous Sarracenia species increase diversity
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8.9
Dactylorhiza majalis (orchids) between Molinia caerulea on a drained oligotrophic lime-fen
8.10
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Mesotrophic wet meadow with Fritillaria meleagris and Cardamine pratensis in the Sinntal Valley, Germany
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CAlcnsivoly culiivjlcd |
injtLi гл 1 shaping1? |
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f«esi IT4lini*Pft«l |
Pti;- |
Ratf«J Bog |
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Fffi as |
CuT п® |
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p^ sb aw meadow |
chtrictori-Mic sprchss:
Pd и Artddfe’di
■ AfictV? j cacnA1 j on tirs ncd straw гкайм = law 5C*3? {G*rfx ctav&&mn} po well grained sL-s-w
* Bffill* ыУ Ot &ЧЇ 3Gd! fCflC
* fffittiflt Зі ■П ИС pCiL СЧІ C Mh
Cv ■ Шнч rutoJris m ih* bog
Pf ■ ftnwt mtiїлійіґі at ip* bo® edga
Ev ■ EriOpfMftvn vJ£-ndfi/.?i Oft LFvfi be^ftUUu
Ищи Vfricifiria/r. nof in:hc &зд-№р
Cr ■ C. ICA roafrdta in ".he 1 jgg
Ag в дл*ії g№w in Ihe Cflrf
Fs ■ F. igvi іуіїккз
8.11
Possible fen and bog types above a silted-up lake in the northern alpine foothills—heights are considerably exaggerated for illustrative purposes
insectivorous Drosera species, growing between Sphagnum mosses. Of course there are several other possibilities of bog-development, for example described in Succow and Jeschke (1986) or Ellenberg (1996).
