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

C-14 ages and delta C-13 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 C-14 ages were in the increasing order: humic acid fraction < humic acid Pg fraction < sclerotium grains. The delta C-13 values for sclerotium grains in surface A horizons and buried A horizons were approximately -31 parts per thousand to -28 parts per thousand, and these values were approximately 2-4 parts per thousand smaller than those of humic acids and soils. The C content of the grains had a tendency to decrease with increasing C-14 ages, while the C content of humic acid was constant with age. The C-14 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 C-14 ages of humic acid. The low delta C-13 values for sclerotium grains have presumably originated from characteristically biological organics, which may be protected from attack in soils because of their structure.