Natural 15N abundance of plants and soil N in a temperate coniferous forest

Keisuke Koba, Muneto Hirobe, Lina Koyama, Ayato Kohzu, Naoko Tokuchi, Knute John Nadelhoffer, Eitaro Wada, Hiroshi Takeda

Research output: Contribution to journalArticlepeer-review

72 Citations (Scopus)


Measurement of nitrogen isotopic composition (δ15N) of plants and soil nitrogen might allow the characteristics of N transformation in an ecosystem to be detected. We tested the measurement of δ15N for its ability to provide a picture of N dynamics at the ecosystem level by doing a simple comparison of δ15N between soil N pools and plants, and by using an existing model. δ15N of plants and soil N was measured together with foliar nitrate reductase activity (NRA) and the foliar NO3- pool at two sites with different nitrification rates in a temperature forest in Japan. δ15N of plants was similar to that of soil NO3- in the high-nitrification site. Because of high foliar NRA and the large foliar NO 3- pool at this site, we concluded that plant δ 15N indicated a great reliance of plants on soil NO3 - there. However, many δ15N of soil N overlapped each other at the other site, and δ15N could not provide definitive evidence of the N source. The existing model was verified by measured δ15N of soil inorganic N and it explained the variations of plant δ15N between the two sites in the context of relative importance of nitrification, but more information about isotopic fractionations during plant N uptake is required for quantitative discussions about the plant N source. The model applied here can provide a basis to compare δ15N signatures from different ecosystems and to understand N dynamics.

Original languageEnglish
Pages (from-to)457-469
Number of pages13
Issue number5
Publication statusPublished - Aug 2003
Externally publishedYes


  • Foliar NO
  • Modeling
  • Nitrate reductase activity
  • Nitrogen availability
  • Nitrogen dynamics
  • Nitrogen isotope ratio

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Environmental Chemistry
  • Ecology


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