| Co-Investigator(Kenkyū-buntansha) |
GARREC J.ーP. フランス政府森林研究センター, 大気汚染研究所, 所長
KUDO Akira National Research Council of Canada, Institute of Environmemtal Chemistry, Divis, 部長
SUGUHARA Masataka Osaka Industrial University, Faculty of Engineering, Professor., 工学部, 教授 (60026119)
YOSHIDA Shigejiro Kagoshima University, Faculty of Agriculture, Associate Professor., 農学部, 助教授 (80128462)
J.-P. Garrec France National Forest Research Center, Laboratry of Atomsphere Pollution, Direc
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| Research Abstract |
Preliminary Analysis of Tree Rings for Historical Changes of Greenhouse Gas (CO_2) Concentrations--Using Japanese-Canadian-French Tree Rings.
In order to pinpoint the causes of recent increase in CO_2 concentrations of the air, tree rings which record long term environmental conditions can be the most reliable method. The plausible causes include : (1) human combustion of the fossil fuels which produce a lower stable carbon isotopic ratio (^<13>C/^<12>C or delta^<13>C), (2) other human activities such as creation of farm land from forest, (3) natural phenomena such as a change of deep ocean current and (4) a combination of the above three. The usage of ice cores determining the concentration changes of CO_2 during the last 1000 years is limited by the low time resolution of air bubble formation.
The cellulose of the late wood in tree rings may have been recording more accurate changes ot the surrounding environmental conditions including CO2 concentrations in the air. Tree rings have not
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only the clear record of the history up to several thousand years but also dead wood could be preserved for many millennium in the natural environment. The data from Germany suggested that the recent rapid CO2 increase was not caused solely by the human activity of fossil fuel burning.
The objective of this investigation was to validate this information using tree rings from Japan. A typical 78 years old sugi tree (Cryptomeria japonica D.Don) was harvested from an environment where temperature, humidity and precipitation are different from those obtained in Europe. The delta^<13>C values were obtained using a mass-spectrometer after the tree rings were separated into 7 samples : (1) 1920-29, (2) 1930-39, .. (7) 1980-88. The delta^<13>C analysis of sample (1), (3), (5) and (7), were -22.31*, -22.65*, -23.35* and -24.03*, respectively. The number of analytical data were limited to four samples, thus it is very difficult to draw substantiated conclusions out of this preliminary investigation. Two findings, however, can be expressed : (1) it is possible to measure delta^<13>C values using Japanese sugi and (2) the obtained delta^<13>C values were in a reasonable range. Less
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