7.2.2.2 ONT and IWK Profiles
Table 7.2 shows AMS14 C dates for sclerotia, humic acid, and humin from the ONT
soil samples. Comparisons of the AMS14 C dates of sclerotia based on grain size and
horizon are shown in Fig. 7.2.
14 C ages for sclerotia in the ONT Ah1 layer were
500–830 year BP. Large sclerotia tended to be older than small sclerotia when
different-sized sclerotia from each layer were individually compared. When
14 C
dates were compared between horizons and grain sizes, larger sclerotia were again
found to be older. The
14 C dates for humin were older than those of sclerotia in the
E/A and Bs horizons, and the
14 C dates for sclerotia were closer to the dates for
humic acid than those for humin.
Figure 7.3 shows the results for sclerotia in Iwaki profile. In the Ah1 layer (Iw-1),
14 C dating of sclerotia indicated that they were modern. Sclerotia from lower
horizons were older, regardless of grain size. Moreover, sclerotia in the B horizon
were dated at almost 3000 year BP (Table 7.3).
7.2.2.3 Changes in Total Carbon Content of Soil, Humic Acid,
and Sclerotia by
14 C Date
Table 7.4 shows total carbon content TC (%) of sclerotia grains, humic acid, and soil
in ONT profile, and Table 7.5 shows TC (%) of sclerotia grains and soil in IWK
profile. Figure 7.4 shows the relationship between the
14 C dates and TC content of
soil samples, humic acid, and sclerotia of medium size in ONT profile. Figure 7.5
shows the
14 C dates and TC content of soil samples and sclerotia of medium size in
IWK profile. The dates of soil samples from the ONT soils were determined based on
the humin
14 C date and those of the IWK soils were based on sclerotia
14
C dates. In
the A horizons, the values for carbon content of sclerotia were about 50 wt%,
whereas in the B layer they were approximately 40 wt%. The carbon content of
sclerotia decreased linearly with time, whereas that of soil decreased logarithmically.
These results clearly indicated that sclerotia, structural bodies, undergo a ubiquitous
decomposition and denaturation process.
7.3 Relationship Between
14
C Age and Al/C Ratio
of Sclerotia Grains
7.3.1 Materials and Methods
7.3.1.1 Sclerotia Samples
Sclerotia, formed by C. geophilum or related species, can easily be identified in soil
samples based on the morphological characteristics reported by Trappe (1969).
Cenococcum geophilum sclerotia were obtained from soil samples collected from
7 Dating of Sclerotia Grains in Andosol Profiles
125
Table 7.2 shows AMS14 C dates for sclerotia, humic acid, and humin from the ONT
soil samples. Comparisons of the AMS14 C dates of sclerotia based on grain size and
horizon are shown in Fig. 7.2.
14 C ages for sclerotia in the ONT Ah1 layer were
500–830 year BP. Large sclerotia tended to be older than small sclerotia when
different-sized sclerotia from each layer were individually compared. When
14 C
dates were compared between horizons and grain sizes, larger sclerotia were again
found to be older. The
14 C dates for humin were older than those of sclerotia in the
E/A and Bs horizons, and the
14 C dates for sclerotia were closer to the dates for
humic acid than those for humin.
Figure 7.3 shows the results for sclerotia in Iwaki profile. In the Ah1 layer (Iw-1),
14 C dating of sclerotia indicated that they were modern. Sclerotia from lower
horizons were older, regardless of grain size. Moreover, sclerotia in the B horizon
were dated at almost 3000 year BP (Table 7.3).
7.2.2.3 Changes in Total Carbon Content of Soil, Humic Acid,
and Sclerotia by
14 C Date
Table 7.4 shows total carbon content TC (%) of sclerotia grains, humic acid, and soil
in ONT profile, and Table 7.5 shows TC (%) of sclerotia grains and soil in IWK
profile. Figure 7.4 shows the relationship between the
14 C dates and TC content of
soil samples, humic acid, and sclerotia of medium size in ONT profile. Figure 7.5
shows the
14 C dates and TC content of soil samples and sclerotia of medium size in
IWK profile. The dates of soil samples from the ONT soils were determined based on
the humin
14 C date and those of the IWK soils were based on sclerotia
14
C dates. In
the A horizons, the values for carbon content of sclerotia were about 50 wt%,
whereas in the B layer they were approximately 40 wt%. The carbon content of
sclerotia decreased linearly with time, whereas that of soil decreased logarithmically.
These results clearly indicated that sclerotia, structural bodies, undergo a ubiquitous
decomposition and denaturation process.
7.3 Relationship Between
14
C Age and Al/C Ratio
of Sclerotia Grains
7.3.1 Materials and Methods
7.3.1.1 Sclerotia Samples
Sclerotia, formed by C. geophilum or related species, can easily be identified in soil
samples based on the morphological characteristics reported by Trappe (1969).
Cenococcum geophilum sclerotia were obtained from soil samples collected from
7 Dating of Sclerotia Grains in Andosol Profiles
125