Physicochemical characteristics and nitrogen metabolism of the peat soil system in Ozegahara under the impacts of flooding

Abstract

　As a part of the 4^th Scientific Research of Ozegahara, physicochemical characteristics and nitrogen metabolism of the peat soil were studied at 39 sites in Ozegahara (July 2017–August 2018). The survey data indicated that the peat soils almost saturated with water were slightly acidic and exhibited high denitrification activity in the soils containing appreciable amounts of NH₄⁺ and NO₃^-. The wet hollow mire sites of the bank-hollow complex near the Yoppi River are characterized by abundant occurrence of Myrica gale var. tomentosa on the mires with abundant available phosphorous in the soils. In this bank-hollow complex, significant correlations were detected among nitrogen metabolic activities, NO₃^- concentration, redox potential, and water level. We also found a significant correlation between nitrogen fixation in the rhizome system of The Myrica and its shrub height in hollow mires. Analysis of these survey data suggested that the active nitrogen fixation activity of The Myrica at the hollow mires under flood-associated phosphorus supply might be a possible cause of the recent extensive increase in The Myrica abundance in Ozegahara. Further detailed studies are needed on the process of flood-associated phosphorus supply to Ozegahara and its effects on nitrogen fixation activity in the rhizome system of The Myrica, as well as nitrogen cycle in the Ozegahara ecosystem.