Origin of string patterns in boreal peatlands

The detailed stratigraphical analyses supported by field observations on mires in Labrador and northern Minnesota reported here provide the basis for an explanation of the development of the surface pattern of alternating peat ridges (strings) and linear depressions or pools (flarks) in boreal fens. The developmental sequence involves: drainage impediment and the concomitant initiation of peat accumulation; development of linear patterns as a result of changing hydrological conditions and differential rates of peat accumulation of hummock and hollow plant communities; and subsequent enlargement and coalescence of pools through the degradation of the underlying peat and the intervening ridges. We show here that many of the processes may be active in the development of the pool patterns on raised bogs as well as on fens.