47 grains (average 33.56 Æ 2.37) per 800 cm
3 soil. Sclerotia from Mt. Iwaki also had
a higher count density, weight, and weight density than those from Mt. Chokai
(Table 2.1).
2.2.2.2 Identification of Sclerotia-Associated Fungi by Molecular
Methods
Extraction of sclerotial DNA with a commercially available DNA extraction kit
produced poor results in terms of both quality and quantity. The phenol/chloroform
method used in this study gave more reliable results but was relatively time consuming. Our analyses identified five species of fungi in the two sites: two from
Mt. Chokai and three from Mt. Iwaki. The fungal community profile of sclerotia
from Mt. Chokai showed one dominant peak (Fig. 2.1), which was identified as
Arthrinium arundinis (Ascomycota: Sordariales), a species described as
dematiaceous or having dark-walled septate hyphae (Pan et al. 2009). Species of
Sordariales were also detected in sclerotia collected from forests dominated by
Quercus and Pinus in Florida and Georgia, USA (Obase et al. 2014), and have
been recognized as one of the soil fungal species responsible for bamboo degradation (Kim et al. 2010). Nakashizuka (1988) reported that the survival rate of
F. crenata seedlings on the floor where dwarf bamboo had withered was markedly
higher than that on the floor where dwarf bamboo survived. Moreover, the removal
of understory dwarf bamboo increased the net carbon gain and transpiration rates of
overstory trees (Kobayashi et al. 2006); therefore, the removal of dwarf bamboo in
relatively young stands may greatly enhance the productivity of overstory trees in
the long term (Ishii et al. 2008). Based on these findings, the presence of A. arundinis
in sclerotia from the beech forest floor on Mt. Chokai is suggested to play an
important role in the survival of F. crenata.
Table 2.1 Soil and sclerotia properties
Soil
Mt. Chokai
Mt. Iwaki
Litter weight (g)
77.7 Æ 13.5
47.9 Æ 6.71
Weight of F and H horizons (g)
287 Æ 32.9
465 Æ 45.5
O horizon thickness (cm)
5.08 Æ 0.36
5.31 Æ 0.03
Bulk density of A horizon (g cm
À3
)
0.45 Æ 0.04
0.35 Æ 0.04
Soil pH (H 2 O)
4.60 Æ 0.09
3.96 Æ 0.04
Soil pH (KCl)
3.88 Æ 0.04
3.44 Æ 0.06
Sclerotia
Mt. Chokai
Mt. Iwaki
Count density (grains g
À1
)
0.14 Æ 0.06
0.16 Æ 0.03
Mean grain weight (mg)
a
0.83 Æ 0.04
1.80 Æ 0.05
Weight density (mg g
À1
)
a
0.11 Æ 0.02
0.29 Æ 0.04
Data are mean Æ standard errors from 9 replicates for soils and 18 replicates for sclerotia.
a p < 0.01;
Student’s t-test
22
K. Narisawa et al.
3 soil. Sclerotia from Mt. Iwaki also had
a higher count density, weight, and weight density than those from Mt. Chokai
(Table 2.1).
2.2.2.2 Identification of Sclerotia-Associated Fungi by Molecular
Methods
Extraction of sclerotial DNA with a commercially available DNA extraction kit
produced poor results in terms of both quality and quantity. The phenol/chloroform
method used in this study gave more reliable results but was relatively time consuming. Our analyses identified five species of fungi in the two sites: two from
Mt. Chokai and three from Mt. Iwaki. The fungal community profile of sclerotia
from Mt. Chokai showed one dominant peak (Fig. 2.1), which was identified as
Arthrinium arundinis (Ascomycota: Sordariales), a species described as
dematiaceous or having dark-walled septate hyphae (Pan et al. 2009). Species of
Sordariales were also detected in sclerotia collected from forests dominated by
Quercus and Pinus in Florida and Georgia, USA (Obase et al. 2014), and have
been recognized as one of the soil fungal species responsible for bamboo degradation (Kim et al. 2010). Nakashizuka (1988) reported that the survival rate of
F. crenata seedlings on the floor where dwarf bamboo had withered was markedly
higher than that on the floor where dwarf bamboo survived. Moreover, the removal
of understory dwarf bamboo increased the net carbon gain and transpiration rates of
overstory trees (Kobayashi et al. 2006); therefore, the removal of dwarf bamboo in
relatively young stands may greatly enhance the productivity of overstory trees in
the long term (Ishii et al. 2008). Based on these findings, the presence of A. arundinis
in sclerotia from the beech forest floor on Mt. Chokai is suggested to play an
important role in the survival of F. crenata.
Table 2.1 Soil and sclerotia properties
Soil
Mt. Chokai
Mt. Iwaki
Litter weight (g)
77.7 Æ 13.5
47.9 Æ 6.71
Weight of F and H horizons (g)
287 Æ 32.9
465 Æ 45.5
O horizon thickness (cm)
5.08 Æ 0.36
5.31 Æ 0.03
Bulk density of A horizon (g cm
À3
)
0.45 Æ 0.04
0.35 Æ 0.04
Soil pH (H 2 O)
4.60 Æ 0.09
3.96 Æ 0.04
Soil pH (KCl)
3.88 Æ 0.04
3.44 Æ 0.06
Sclerotia
Mt. Chokai
Mt. Iwaki
Count density (grains g
À1
)
0.14 Æ 0.06
0.16 Æ 0.03
Mean grain weight (mg)
a
0.83 Æ 0.04
1.80 Æ 0.05
Weight density (mg g
À1
)
a
0.11 Æ 0.02
0.29 Æ 0.04
Data are mean Æ standard errors from 9 replicates for soils and 18 replicates for sclerotia.
a p < 0.01;
Student’s t-test
22
K. Narisawa et al.