Mires of spring or seep systems of boreal and nemoral Europe fed by lime-rich waters over sand or gravel soils physiognomically dominated by the presence, alongside Cratoneurion commutati formations, of communities belonging to or related to arcto-alpine riverine swards (unit D4.2) or subalpine willowherb stream communities (unit C3.55) comprising in particular stands of the perennial horsetail Equisetum variegatum.