7.1 Introduction
Accelerator mass spectrometry (AMS)–
14 C dating requires at least 1 mg of graphite
for measurements. Since Cenococcum geophilum sclerotia grains are composed of
approximately 50% carbon and some found in forest soils are approximately
0.5–5 mm in diameter and have a mass as large as 2 mg,
14 C dates can be obtained,
even for single grains (Watanabe et al. 2004a, b). Sclerotia of C. geophilum are used
as decay-resistant markers of the paleoenvironment in paleopedology, geochemistry,
and sedimentology. Hormes et al. (2004) examined the C. geophilum spores in
paleosols of moraines in Lapland, northern Sweden, and reported that the
14 C ages
of the spores were 5000–6000 year BP (Note, however, that the “spores” were
actually sclerotia; C.geophilum does not produce spores according to LoBuglio
1999). Benedict (2011) reported evidence of a shift in tree limit by studying
sediment samples from the Rocky Mountains, Colorado, USA, where charred
C. geophilum sclerotia with a median diameter of 1.1 mm were demonstrated to
have radiocarbon dates of 4770 Æ 25 year BP.
Cenococcum geophilum sclerotia can contribute significantly to the fungal biomass of forest environments and thus represent an important source of carbon
assimilated from host species (LoBuglio 1999). As extramatrical mycelia represent
a considerable biomass component and potential carbon sink in many forest soils,
Cairney (2012) reviewed the estimates of mean, median, and maximum longevities
of ectomycorrhizal roots, sclerotia, and mycelia in the field to discuss turnover of
carbon stored in ectomycorrhizal root and mycelial biomass.
Samples of C. geophilum sclerotia grains, humic acid, and humin fractions from
three different Andosol profiles soils were examined to measure their AMS14 C
dates. We discuss the implications of the AMS14 C ages and carbon turnover in
sclerotia.
7.2
14
C Ages of Sclerotia Grains in Three Andosol Profiles
7.2.1 Materials and Methods
Soil samples were collected from three Andosol profiles (MYK, ONT, and IWK) for
analysis of sclerotia grains and extraction of humic acid and humin. The Myoko
profile (MYK) is a Fulvic Andosol, WRB/FAO-Unesco, located in central Japan
(36
54
0 N 138
8
0 E, elevation: 1330 m, vegetation: Fagus crenata), which is comprised of a surface A horizon and buried humic horizons beneath KG-b: Koyaike
ash-b and KG-c: Koyaike ash-c, tephra deposits derived from eruptions of the
Yakeyama volcano in 650 Æ 100 year BP and 950 Æ 80 year BP (Hayatsu et al.
1994), respectively. The ONT profile is an Andic Podzol on Mt. Ontake in Gifu
Prefecture, beneath Abies veitchii and Tsuga diversifolia forests (35
55
0 11
00 N,
137
27
0 53
00 E; elevation: 2100 m). Soil samples were taken from each horizon of
120
M. Watanabe et al.
Accelerator mass spectrometry (AMS)–
14 C dating requires at least 1 mg of graphite
for measurements. Since Cenococcum geophilum sclerotia grains are composed of
approximately 50% carbon and some found in forest soils are approximately
0.5–5 mm in diameter and have a mass as large as 2 mg,
14 C dates can be obtained,
even for single grains (Watanabe et al. 2004a, b). Sclerotia of C. geophilum are used
as decay-resistant markers of the paleoenvironment in paleopedology, geochemistry,
and sedimentology. Hormes et al. (2004) examined the C. geophilum spores in
paleosols of moraines in Lapland, northern Sweden, and reported that the
14 C ages
of the spores were 5000–6000 year BP (Note, however, that the “spores” were
actually sclerotia; C.geophilum does not produce spores according to LoBuglio
1999). Benedict (2011) reported evidence of a shift in tree limit by studying
sediment samples from the Rocky Mountains, Colorado, USA, where charred
C. geophilum sclerotia with a median diameter of 1.1 mm were demonstrated to
have radiocarbon dates of 4770 Æ 25 year BP.
Cenococcum geophilum sclerotia can contribute significantly to the fungal biomass of forest environments and thus represent an important source of carbon
assimilated from host species (LoBuglio 1999). As extramatrical mycelia represent
a considerable biomass component and potential carbon sink in many forest soils,
Cairney (2012) reviewed the estimates of mean, median, and maximum longevities
of ectomycorrhizal roots, sclerotia, and mycelia in the field to discuss turnover of
carbon stored in ectomycorrhizal root and mycelial biomass.
Samples of C. geophilum sclerotia grains, humic acid, and humin fractions from
three different Andosol profiles soils were examined to measure their AMS14 C
dates. We discuss the implications of the AMS14 C ages and carbon turnover in
sclerotia.
7.2
14
C Ages of Sclerotia Grains in Three Andosol Profiles
7.2.1 Materials and Methods
Soil samples were collected from three Andosol profiles (MYK, ONT, and IWK) for
analysis of sclerotia grains and extraction of humic acid and humin. The Myoko
profile (MYK) is a Fulvic Andosol, WRB/FAO-Unesco, located in central Japan
(36
54
0 N 138
8
0 E, elevation: 1330 m, vegetation: Fagus crenata), which is comprised of a surface A horizon and buried humic horizons beneath KG-b: Koyaike
ash-b and KG-c: Koyaike ash-c, tephra deposits derived from eruptions of the
Yakeyama volcano in 650 Æ 100 year BP and 950 Æ 80 year BP (Hayatsu et al.
1994), respectively. The ONT profile is an Andic Podzol on Mt. Ontake in Gifu
Prefecture, beneath Abies veitchii and Tsuga diversifolia forests (35
55
0 11
00 N,
137
27
0 53
00 E; elevation: 2100 m). Soil samples were taken from each horizon of
120
M. Watanabe et al.