| Budget Amount *help |
¥3,300,000 (Direct Cost: ¥3,300,000)
Fiscal Year 2006: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2005: ¥1,900,000 (Direct Cost: ¥1,900,000)
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| Research Abstract |
Sclerotium grains, the resting structure of an ectomycorrhizal fungus, Cenococcum geophilum, were examined in this study to clarify the processes of formation, development and extinguishment of sclerotium grains in forest soils. AMS C<14> and δC^<13> were examined for sclerotium grains together with humic acids to, elucidate the characteristics of these grains distributed in forest soils. The C^<14> age of the grains remaining in surface A horizon was obtained as>ca 3, 000 years. The ages of humic acids extracts, including humic acid Pg, were slightly younger than sclerotium grains. The δC^<13> values for sclerotium grains in surface A horizons were smaller than those of humic acids and soils. As there was no relation with grain size and C^<14> ages, it was considered that the grains so called dead sclerotium do not develop their volume in soil. The carbon content of the grain had a tendency to decrease along with an increase of C^<14> ages, although carbon content of humic acid was co
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nstant against age. The C^<14> ages of sclerotium grains indicate the individual age of grain formation, while those of humic acid indicate the mean residue age of heterogeneous organic substances. The mean concentrations of major elements in sclerotium grains were quantitatively defined as C (47.6%), O (30.2%), H (3.32%), Al (1.4%), N (0.78%), and carbon in sclerotium grains took the form of large amounts of O-alkyl C, and was also associated with aromatic C and methyl C, which strongly showed a characteristically biological origin and completely different spectral features to humic acids from an allophonic Andosol. Therefore the low δC^<13> values for sclerotium grains are presumably originated by characteristically biological organics. Microbial analysis performed higher diversity of bacteria communities compared with soil environment. The AMS C^<14> age values obtained for sclerotium grains proved its stability and long life as a shelter for microorganisms, and preserve their diversity under a severe environment. Probably, microorganisms inside the grains are responsible for the extinguishment of the grain in terms of decreasing the content of carbon inside the grain. Although the findings we have are still very limited, the goal of the study is to understand further implications of sclerotium formation in a soil ecosystem, which will help us to learn what strategy is necessary for biota to survive a catastrophe. Less
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