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The soil in the forest is involved with many important carbon reservoirs. Decomposition rate and turn over time of the soil organic matter, which are important factors for carbon cycle in the biosphere, have been evaluated by an analysis of the carbon isotopic ratio in the soil. The following observation were carried out in the forest in the Nagoya Univ. ersity: Vertical profies of organic matter contents in soil and carbon dioxide (CO_2) concentrations in soil air and CO_2 flux from the soil and their ^<14>C specific activities of the CO_2 flux from the soil. Carbon-14 specific activities of soil organic matter at 0-10 cm depth were 10-60 mBq gC^<-1> higher than that of atmospheric CO_2. The enrichment of ^<14>C would be attributed nuclear testings. Contrastingly, ^<14>C specific activities of CO_2 of soil air were almost to that of the atmospheric CO_2, and their depth distributions to 120cm were almost uniform. Carbon-14 specific activities of CO_2 of the surface soil air and of CO_2 fluxes from soil to the atmosphere were 246 mBq gC^<-1> and 244-265 mBq gC^<-1>, respectively. Soil organic matter and CO_2 flux with ^<14>C specific activity were higher than that of atmospheric CO_2. Using the difference of ^<14>C specific activities between CO_2 produced by root respiration and CO_2 from organic matter decomposition, the decomposition rate of soil organic matter is calculated with 8.7×10^<-1> kgCO_2 kgC^<-1>h^<-1>, the turn over time is estimated with 48 years.
タンデトロン加速器質量分析計業績報告 Summaries of Researches Using AMS 2003 (平成15)年度
名古屋大学加速器質量分析計業績報告書 15 165-173, 2004-03