yeast in soil may not be common in natural environment as the combination of
conditions that permit xylose synthesis by yeasts in pre-dried soil are unlikely to
occur naturally.
In summary, the neutral saccharide composition of microbially synthesized polysaccharides in soil depends on which microbial species thrive with addition of a
given substrate, as well as how these microbes are affected by both soil properties
such as acidity and incubation conditions such as temperature and pretreatment of
soil. Incubation experiments using tracer techniques have shown that the polysaccharides synthesized in soil by microorganisms are dominated by hexoses rather than
pentoses.
6.4 Accumulation of Microbial Polysaccharides
in Forest Soil
The monosaccharide composition of forest soil and forest-derived arable soil differs
from that of non-forest soil (Fig. 6.3). Figure 6.3 does not include forest soil with an
origin other than volcanic ash, as no data is available. The proportion of EH-glucose
and mannose in forest soil and forest-derived arable soil is significantly larger than in
non-forest soil, including prairie and grassland soil. The proportions of
NEH-glucose, arabinose, and xylose are the opposite. Proportions of galactose and
rhamnose have no significant difference between forest and forest derived arable soil
and non-forest soil.
The monosaccharide composition is illustrated by the molar ratio of GM/AX
(Fig. 6.4). Forest soil and forest-derived arable soil have a higher GM/AX ratio than
non-forest soil, irrespective of parent materials. The data for forest soil and forestderived arable soil of volcanic ash origin are biased towards those with a high SOM
content, but non-volcanic ash forest soil with a low SOM content has also a
significantly higher molar ratio of GM/AX than non-forest soil (Fig. 6.4). Then,
monosaccharide composition tends to differ between forest soils including forestderived arable soils and non-forest soils. In comparison to non-forest soil, forest soil
and forest-derived arable soil contain more microbial polysaccharide than plant
polysaccharides.
Forest soil and forest-derived arable soil of volcanic ash have a significantly
higher GM/AX ratio than forest soil of non-volcanic ash (Fig. 6.4). This suggests the
former soil may have accumulated more abundantly microbial polysaccharides than
the latter soil. This difference can be ascribed in part to a larger organic matter
accumulative ability of volcanic ash soil than that of non-volcanic ash soil
(Murayama 1980). A field experiment on decomposability of indigenous soil saccharides by glass fiber bag method for 2 and/or 3 years showed that galactose,
EH-glucose, fucose, and rhamnose in forest-derived arable soil of volcanic ash are
more stable (Murayama 1984b) than those components in arable soil of non-volcanic
ash (Murayama 1981).
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S. Murayama and Y. Sugiura
conditions that permit xylose synthesis by yeasts in pre-dried soil are unlikely to
occur naturally.
In summary, the neutral saccharide composition of microbially synthesized polysaccharides in soil depends on which microbial species thrive with addition of a
given substrate, as well as how these microbes are affected by both soil properties
such as acidity and incubation conditions such as temperature and pretreatment of
soil. Incubation experiments using tracer techniques have shown that the polysaccharides synthesized in soil by microorganisms are dominated by hexoses rather than
pentoses.
6.4 Accumulation of Microbial Polysaccharides
in Forest Soil
The monosaccharide composition of forest soil and forest-derived arable soil differs
from that of non-forest soil (Fig. 6.3). Figure 6.3 does not include forest soil with an
origin other than volcanic ash, as no data is available. The proportion of EH-glucose
and mannose in forest soil and forest-derived arable soil is significantly larger than in
non-forest soil, including prairie and grassland soil. The proportions of
NEH-glucose, arabinose, and xylose are the opposite. Proportions of galactose and
rhamnose have no significant difference between forest and forest derived arable soil
and non-forest soil.
The monosaccharide composition is illustrated by the molar ratio of GM/AX
(Fig. 6.4). Forest soil and forest-derived arable soil have a higher GM/AX ratio than
non-forest soil, irrespective of parent materials. The data for forest soil and forestderived arable soil of volcanic ash origin are biased towards those with a high SOM
content, but non-volcanic ash forest soil with a low SOM content has also a
significantly higher molar ratio of GM/AX than non-forest soil (Fig. 6.4). Then,
monosaccharide composition tends to differ between forest soils including forestderived arable soils and non-forest soils. In comparison to non-forest soil, forest soil
and forest-derived arable soil contain more microbial polysaccharide than plant
polysaccharides.
Forest soil and forest-derived arable soil of volcanic ash have a significantly
higher GM/AX ratio than forest soil of non-volcanic ash (Fig. 6.4). This suggests the
former soil may have accumulated more abundantly microbial polysaccharides than
the latter soil. This difference can be ascribed in part to a larger organic matter
accumulative ability of volcanic ash soil than that of non-volcanic ash soil
(Murayama 1980). A field experiment on decomposability of indigenous soil saccharides by glass fiber bag method for 2 and/or 3 years showed that galactose,
EH-glucose, fucose, and rhamnose in forest-derived arable soil of volcanic ash are
more stable (Murayama 1984b) than those components in arable soil of non-volcanic
ash (Murayama 1981).
106
S. Murayama and Y. Sugiura