retained all of the major components found in SG from the O horizon, with similar
relative abundance. This indicates that SG plays a role as reservoirs of polysaccharides (Sugiura et al. 2017). The differences in the content and composition of SG
saccharides between the O and A1 horizons were ascribed in part to the greater
relative abundance of viable sclerotia in the O horizon.
The molar ratio of GM/AX of SG saccharides ranged from 7.5 to 25 and was
much higher than that of matrix soil (Table 6.2). The ratio of EH-glucose/NEHglucose was also much larger than that of matrix soil. Thus accumulation of SG
saccharides has contributed to increase these two ratios of forest soil.
ECM fungal sclerotia were not observed to incorporate roots or root hairs,
although they were formed very close to pine roots (Grenville et al. 1985). Therefore
NEH-glucose was inferred to be released not from plant cellulose but from the
complex fungal cell wall polysaccharides comprised from ß (1, 3) (1, 6) glucan
linked to chitin (cf. Sect. 6.3.2) (Sugiura et al. 2017) The NEH-glucose in soil
hydrolysates has been considered to originate from plant cellulose. However, SG
is also a source of the NEH-glucose in forest soil hydrolysates.
In addition, the saccharides determined in SG may originate also in part from
non-ECM fungal saccharides besides SG saccharides (Sugiura et al. 2017). As old
and/or dead SG provide a habitat for bacteria (Ohta et al. 2003) and fungi (Obase
et al. 2014; Amasya et al. 2015).
6.5.2.3 Quantitative Comparison of Saccharides in ECM Fungal SG
to Those in Whole Soil: A Case Study
The total sugar components and EH-glucose in SG from O horizon accounted for
1.9% and 3.6% of those in the soil, respectively (Table 6.3). These results may apply
only to the soil at the sampling site in the summer, as the contents of ECM fungal SG
differ among forests (Watanabe et al. 2004; Sakagami 2011) and fluctuate with the
seasons (Vogt et al. 1981; Lussenhop and Fogel 1999; Sakagami 2011). No comparable data which determined proportion of neutral saccharides of biomass or
biomass remains collected from soil as specified microbial species or groups, such
as ECM fungal sclerotia in this study, to soil neutral saccharides is known. Although
the proportion of SG saccharides to soil ones appears to be small (Table 6.3), we
consider it is substantial. As ECM fungal SG are produced by a limited number of
species of the vast number of microbial species inhabiting forest soil. It should also
be noted that this proportion was obtained only for SG larger than 0.2 mm, although
forest soil also contains smaller SG. Trappe (1969) reported live sclerotia vary from
0.05 to 4 or more mm in diameter.
6 Origin of Soil Polysaccharides, and Ectomycorrhizal Fungal Sclerotia as Sources . . .
111
relative abundance. This indicates that SG plays a role as reservoirs of polysaccharides (Sugiura et al. 2017). The differences in the content and composition of SG
saccharides between the O and A1 horizons were ascribed in part to the greater
relative abundance of viable sclerotia in the O horizon.
The molar ratio of GM/AX of SG saccharides ranged from 7.5 to 25 and was
much higher than that of matrix soil (Table 6.2). The ratio of EH-glucose/NEHglucose was also much larger than that of matrix soil. Thus accumulation of SG
saccharides has contributed to increase these two ratios of forest soil.
ECM fungal sclerotia were not observed to incorporate roots or root hairs,
although they were formed very close to pine roots (Grenville et al. 1985). Therefore
NEH-glucose was inferred to be released not from plant cellulose but from the
complex fungal cell wall polysaccharides comprised from ß (1, 3) (1, 6) glucan
linked to chitin (cf. Sect. 6.3.2) (Sugiura et al. 2017) The NEH-glucose in soil
hydrolysates has been considered to originate from plant cellulose. However, SG
is also a source of the NEH-glucose in forest soil hydrolysates.
In addition, the saccharides determined in SG may originate also in part from
non-ECM fungal saccharides besides SG saccharides (Sugiura et al. 2017). As old
and/or dead SG provide a habitat for bacteria (Ohta et al. 2003) and fungi (Obase
et al. 2014; Amasya et al. 2015).
6.5.2.3 Quantitative Comparison of Saccharides in ECM Fungal SG
to Those in Whole Soil: A Case Study
The total sugar components and EH-glucose in SG from O horizon accounted for
1.9% and 3.6% of those in the soil, respectively (Table 6.3). These results may apply
only to the soil at the sampling site in the summer, as the contents of ECM fungal SG
differ among forests (Watanabe et al. 2004; Sakagami 2011) and fluctuate with the
seasons (Vogt et al. 1981; Lussenhop and Fogel 1999; Sakagami 2011). No comparable data which determined proportion of neutral saccharides of biomass or
biomass remains collected from soil as specified microbial species or groups, such
as ECM fungal sclerotia in this study, to soil neutral saccharides is known. Although
the proportion of SG saccharides to soil ones appears to be small (Table 6.3), we
consider it is substantial. As ECM fungal SG are produced by a limited number of
species of the vast number of microbial species inhabiting forest soil. It should also
be noted that this proportion was obtained only for SG larger than 0.2 mm, although
forest soil also contains smaller SG. Trappe (1969) reported live sclerotia vary from
0.05 to 4 or more mm in diameter.
6 Origin of Soil Polysaccharides, and Ectomycorrhizal Fungal Sclerotia as Sources . . .
111