¹⁴C ages and δ¹³C of sclerotium grains found in forest soils

Abstract

¹⁴C ages and δ¹³C were examined for sclerotium grains to elucidate the characteristics of these grains distributed in forest soils. The ages of the grains from surface A horizons and buried A horizons were ca 100–200 bp and ca 300–1,200 bp, respectively. In comparison with humic acid extracts, the ¹⁴C ages were in the increasing order: humic acid fraction < humic acid Pg fraction < sclerotium grains. The δ¹³C values for sclerotium grains in surface A horizons and buried A horizons were approximately −31‰ to −28‰, and these values were approximately 2–4‰ smaller than those of humic acids and soils. The C content of the grains had a tendency to decrease with increasing ¹⁴C ages, while the C content of humic acid was constant with age. The ¹⁴C ages of sclerotium grains indicate the individual age of grain formation, which are more likely to assign closer ages to the beginning of soil forming than the ¹⁴C ages of humic acid. The low δ¹³C values for sclerotium grains have presumably originated from characteristically biological organics, which may be protected from attack in soils because of their structure.

Key words:

• ¹⁴C age
• δ¹³C
• humic acid
• humic acid Pg fraction
• sclerotium grain

ACKNOWLEDGMENTS

The authors thank the Sumitomo Science Foundation and the Japan Society for the Promotion of Science for their financial support for this study.