Calcareous quaking mire

Very wet mires with rich fen vegetation of topogenic basins fed by calcareous ground water from the catchment. Water pH is always high (pH 6.5-8.5) due to high alkalinity. Calcium concentrations are typically very high (>20 mg/l) but sometimes lower, especially in boreal regions. Peat layer is usually relatively thin (0.5-2 m) but also sites with thicker peat layer occur, as depending on basin and catchment topography. Calcium precipitation can take place on peat surface. Water table is always close to peat surface and open water surfaces are common. Regular surface patterning can be absent, while irregular patterns of flarks, pools and hollows are common. In boreal region, typical string-flark patterning is common. In such cases, calcareous quaking mires differ from D3.2 Aapa mires by the abundance of calciphilous species, especially among bryophytes. This also is the main distinction from D2.3a Quaking mires.

Vegetation is strongly minerotrophic and characterized by abundance of Amblystegiaceae mosses, especially Scorpidium scorpioides. Other characteristic mosses include Scorpidium revolvens, Scorpidium cossoni, Calliergon richardsonii and Pseudocalliergon trifarium. In the boreal region, weaker minerotrophy indicating species like Sphagnum contortum and Warnstorfia procera can also be frequent. Vascular plant cover is characteristically sparse. Typical species include Carex chordorrhiza, Carex diandra, Carex flava, Carex lasiocarpa, Carex limosa, Carex rostrata, Carex livida, Drosera longifolia, Equisetum fluviatile, Eriophorum gracile, Juncus stygius, Liparis loeselii, Menyanthes trifoliata, Pedicularis palustris, Potentilla palustris, Schoenus ferrugineus and Utricularia intermedia. Sometimes sparse stands of Phragmites australis are found.

Indicators of good quality:

Under natural conditions, water table is close to surface and it can always be readily observed. Open water surfaces are common. Calcite precipitation takes place in richly calcareous situations, but when calcium levels are not supersaturated, precipitation can be absent. Rich fen mosses are abundant, although not necessarily forming continuous carpets. Sphagnum mosses are mainly absent from main mire surfaces, while they may be found in hummock strings or other isolated microsites. Vascular plant cover is sparse, leaving space and light for mosses.

Drainage ditches can affect calcareous quaking mires by lowering water level or by interrupting the inflow of calcareous water from the catchment. In such cases, rich fen mosses are rapidly lost and replaced by generalist species. Eutrophication by nitrogen deposition also threatens these habitats. Over growth e.g. by Sphagnum subnitens and Calliergonella cuspidata have been observed in high N deposition areas. General increase of vascular plant biomass can also indicate weakening of habitat quality.

Synthesis of Red List assessment

Confidence in the assessment

Pressures and threats