Estimation of the acutual gross nitrification rate in forest soils using stable isotope information

2014 Fiscal Year Final Research Report

• Project/Area Number: 24658133
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Forest science
• Research Institution: Kyoto University (2014); The University of Tokyo (2012-2013)
• Principal Investigator: OHTE Nobuhito 京都大学, 情報学研究科, 教授 (10233199)
• Co-Investigator(Kenkyū-buntansha): TOKUCHI Naoko 京都大学, フィールド科学教育研究センター, 教授 (60237071)
• Project Period (FY): 2012-04-01 – 2015-03-31
• Keywords: 森林生態系 / 窒素循環 / 安定同位体 / 硝化 / 総硝化量 / 不動化量

Outline of Final Research Achievements

The aim of this study was to elucidate the actual gross nitrification rate of forest soils using isotope tracer techniques, which could not be measured by conventional incubation approach. We proposed combined usage of the d18O of NO3- measurements of field water samples and the pool dilution method using 15N tracers. Experimental results at the University of Tokyo, Tanashi Forest showed that the d18O of NO3- decreased drastically at the organic litter layer and the surface part of mineral soil horizon. This indicated that the NO3- supplied by atmospheric deposition was rapidly immobilized and replaced by the NO3- produced by nitrifying microbes. The gross nitrification and immobilization rates measured using the pool dilution method evidenced the NO3- replacement processes consistently.

Free Research Field

森林生態学、水文学、生物地球化学