Seasonal changes in redox properties of peat, nutrition and phenology of Menyanthes trifoliata L. in a floating peat mat in Mizorogaike Pond, central Japan

Abstract

Seasonal changes in leaf population per area, nutrient absorption rate and elemental concentration of Menyanthes trifoliata L. were studied in a floating peat mat in Mizorogaike Pond, central Japan, with reference to the peat redox potential. Leaf population of M. trifoliata showed a rapid increase in May, reached the maximum in June, and then decreased to 12% of the maximum density in July. The foliage density of M. trifoliata again increased and reached its second maximum in September, and then it decreased to zero in December. The decrease of the foliage density from June to July corresponded to the minimum of redox potential (Eh) of the surface peat. Low Eh in the rhizosphere of M. trifoliata relates to the temporary disappearance of the foliage of the plant from June to July. Nutrient concentration (K, Mg, Ca, Fe) in M. trifoliata roots showed minimum in June to August. The nutrient absorption rate of M. trifoliata evaluated from the rubidium absorption rate of excised root of M. trifoliata showed a minimum value in June and July. Peat redox properties would affect the nutrient absorption activity of the roots and the consequent foliage phenology of M. trifoliata in Mizorogaike Pond.