Arable soil developed from prairies and grassland had a significantly lower
GM/AX ratio than forest and forest-derived arable soil, irrespective of SOM content
(Fig. 6.4). These soils may contain fewer microbial polysaccharides relative to plant
polysaccharides than forest and forest-derived arable soils.
We observed a positive relationship between the ratio of EH-glucose/NEHglucose and the molar ratio of GM/AX (Fig. 6.5). In both herbaceous and woody
plant materials, these ratios are low (Table 6.1), indicating that the higher these
ratios, the lower the relative abundance of plant-derived polysaccharides in soil.
Woody plant materials contain galactose and mannose by considerable proportion (Fig. 6.2, Shädel et al. 2010). But, contribution of galactose and mannose from
woody plants to forest soil saccharides, if any might be small. If the original polysaccharides in woody plant materials are directly, without decomposition by
microbes, remaining in soil and make up a large part of forest soil polysaccharides,
forest soil should have large proportion of NEH-glucose and small EH-glucose/
NEH-glucose ratio. But, these features were not observed in the monosaccharide
composition of forest soils (Figs. 6.3, 6.4 and 6.5). Most of plant litter enters the soil
above ground in forest soil, where it forms a humus layer. There, carbohydrates are
preferentially mineralized in course of humification, thus organic matter entering
mineral soil is depleted in carbohydrates (Kögel-Knabner et al. 1988; Guggenberger
et al. 1994).
Thus, forest soil and forest-derived arable soil, irrespective of soil parent materials and SOM content, accumulated more microbial polysaccharides than non-forest
soil. Though, immature forest soils of sand dune and high elevation forest of
creeping pine zone are not included in this conclusion, as SOM of these forest
soils are mostly constituted of woody plant debris.
6.5 ECM Fungal Sclerotia as Sources of Forest Soil
Polysaccharides
Ectomycorrhizal fungi are ubiquitous in forest ecosystems and form a vital component of the plant-soil interface by forming mutualistic mycorrhizal association with
vascular plants, mostly woody plants. A range of ECM genera, including
Cenococcum, Cortinarius, Entroma, Hebeloma, Boletus, Leccinum, Gyrodon,
Paxillus, Pisolithus, Scleroderma, and Austropaxillus, form hypogenous dormant
propagules called sclerotia (Massicotte et al. 1992; Smith et al. 2014) as referred by
Sugiura et al. (2017). Cenococcum geophilum forms abundant black spherical
sclerotia (Trappe 1969; Grenville et al. 1985; Massicotte et al. 1992).
6 Origin of Soil Polysaccharides, and Ectomycorrhizal Fungal Sclerotia as Sources . . .
107
GM/AX ratio than forest and forest-derived arable soil, irrespective of SOM content
(Fig. 6.4). These soils may contain fewer microbial polysaccharides relative to plant
polysaccharides than forest and forest-derived arable soils.
We observed a positive relationship between the ratio of EH-glucose/NEHglucose and the molar ratio of GM/AX (Fig. 6.5). In both herbaceous and woody
plant materials, these ratios are low (Table 6.1), indicating that the higher these
ratios, the lower the relative abundance of plant-derived polysaccharides in soil.
Woody plant materials contain galactose and mannose by considerable proportion (Fig. 6.2, Shädel et al. 2010). But, contribution of galactose and mannose from
woody plants to forest soil saccharides, if any might be small. If the original polysaccharides in woody plant materials are directly, without decomposition by
microbes, remaining in soil and make up a large part of forest soil polysaccharides,
forest soil should have large proportion of NEH-glucose and small EH-glucose/
NEH-glucose ratio. But, these features were not observed in the monosaccharide
composition of forest soils (Figs. 6.3, 6.4 and 6.5). Most of plant litter enters the soil
above ground in forest soil, where it forms a humus layer. There, carbohydrates are
preferentially mineralized in course of humification, thus organic matter entering
mineral soil is depleted in carbohydrates (Kögel-Knabner et al. 1988; Guggenberger
et al. 1994).
Thus, forest soil and forest-derived arable soil, irrespective of soil parent materials and SOM content, accumulated more microbial polysaccharides than non-forest
soil. Though, immature forest soils of sand dune and high elevation forest of
creeping pine zone are not included in this conclusion, as SOM of these forest
soils are mostly constituted of woody plant debris.
6.5 ECM Fungal Sclerotia as Sources of Forest Soil
Polysaccharides
Ectomycorrhizal fungi are ubiquitous in forest ecosystems and form a vital component of the plant-soil interface by forming mutualistic mycorrhizal association with
vascular plants, mostly woody plants. A range of ECM genera, including
Cenococcum, Cortinarius, Entroma, Hebeloma, Boletus, Leccinum, Gyrodon,
Paxillus, Pisolithus, Scleroderma, and Austropaxillus, form hypogenous dormant
propagules called sclerotia (Massicotte et al. 1992; Smith et al. 2014) as referred by
Sugiura et al. (2017). Cenococcum geophilum forms abundant black spherical
sclerotia (Trappe 1969; Grenville et al. 1985; Massicotte et al. 1992).
6 Origin of Soil Polysaccharides, and Ectomycorrhizal Fungal Sclerotia as Sources . . .
107