Seasonal change in the redox property of peat and its relation to vegetation in a system of floating mat and pond

A relationship was sought between species distribution and seasonal change in the redox property of peat in a floating mat in Mizorogaike Pond, central Japan. The mat surface experienced an annual submergence-emergence cycle due to its sinking-rising movement. Redox potential (Eh) of the surface peat showed little difference between communities in the mat in the submergence season (January–June) and early emergence season (July–August). However variation in Eh among communities was clear in the late emergence season (September–December). Among seven communities in the floating mat, theMenyanthes trifoliata-Rhynchospora fauriei, M. trifoliata-Eriocaulon sikokianum-E. bondoense f.pilosum, Sphagnum cuspidatum andM. trifoliata-Carex thunbergii communities had high Eh (400–600 mV) in the late emergence season, while theMenyanthes trifoliata andPhragmites australis-M. trifoliata communities had lower Eh (200–400 mV). TheM. trifoliata-Isachné globosa community was intermediate (300–500 mV). The earlier the emergence of the peat surface began, the higher the Eh became in the late emergence season.