3.2.2.2 Community Profiles of Fungi Consumed by Soil Mesofauna
T-RFLP profiles of fungi extracted from forest soil mesofauna are shown in
Figs. 3.4, 3.5, 3.6 and 3.7. The x-axis shows fragment size, with each distinct
fragment length representing a distinct fungal species. The peak heights on the yaxis show the abundance of that fungal taxon in the mesofauna. Acari at Akita
(Fig. 3.5) showed a peak only for Laccaria sp. Acari at Nagano (Fig. 3.7) also
showed a dominant peak for Laccaria sp., and Collembola showed a dominant peak
for Paxillus sp.
3.2.2.3 Predominance of Acari and Collembola and Their Roles
in the Soil Ecosystem
Insects in the order Oribatida (Acari), identified by having fungivorous mouth parts,
were selected for further study, and Acari with other types of mouth parts (e.g.,
chelate or subchelate pedipalps) were not included in this analysis. Most of the
Collembola found belonged to the family Entomobrydae (69%) and the rest
belonged to the order Poduromorpha (31%). The length of the Acari collected
ranged from 0.6 to 0.9 mm, whereas Collembola were 1.3–1.5 mm in length. The
litter layer at the Nagano sampling site had the highest average weight, and
mesofaunal abundance was also highest at this site (Fig. 3.8). The number of
individuals was correlated to the average weight of the litter layer, and as litter
weight increased, the abundance of both Acari and Collembola tended to increase.
The mean abundance of Acari and Collembola in this study, conducted in temperate
deciduous forests, translates to a density of 11,043 individuals/m
2 and 10,774
individuals/m
2 , respectively. These values are lower than those reported for most
temperate areas of central Japan (Hijii 1994) and some tropical sites (e.g., Seastedt
1984; Gonzalez et al. 2001). At the Chokai and Iwaki sites, Acari were more
abundant. Greater abundance of Acari than Collembola in forests of central Japan
has been reported previously, and the authors proposed this trend was related to the
heavy rainfall, acidic soil, large amount of litter accumulation, and slow decomposition rate (Takeda and Abe 2001; Lin et al. 2002). At the Akita and Nagano sites,
Acari were less abundant than Collembola, in accordance with the findings of Hijii
(1994), who reported on the ratio of springtails to mites in coniferous forests of
Japan. Using our estimates of the proportion of each type of mesofauna at each site,
we estimated the quantity of each fungal species consumed by each group in each
area, based on RFLP peak heights (Fig. 3.9). Not only did Acari and Collembola
predominate in abundance, but their intake of ectomycorrhizal fungi was highest
among all groups of mesofauna. This result shows that Acari and Collembola play a
major role in the regulation of ectomycorrhizal fungi in forest soils.
We also investigated whether the fungal communities extracted from Acari and
Collembola significantly differed from those extracted from other soil mesofauna.
Figure 3.10 shows the results of R-analysis with a stress value of 0.0078, suggesting
42
A. Amasya and K. Narisawa
T-RFLP profiles of fungi extracted from forest soil mesofauna are shown in
Figs. 3.4, 3.5, 3.6 and 3.7. The x-axis shows fragment size, with each distinct
fragment length representing a distinct fungal species. The peak heights on the yaxis show the abundance of that fungal taxon in the mesofauna. Acari at Akita
(Fig. 3.5) showed a peak only for Laccaria sp. Acari at Nagano (Fig. 3.7) also
showed a dominant peak for Laccaria sp., and Collembola showed a dominant peak
for Paxillus sp.
3.2.2.3 Predominance of Acari and Collembola and Their Roles
in the Soil Ecosystem
Insects in the order Oribatida (Acari), identified by having fungivorous mouth parts,
were selected for further study, and Acari with other types of mouth parts (e.g.,
chelate or subchelate pedipalps) were not included in this analysis. Most of the
Collembola found belonged to the family Entomobrydae (69%) and the rest
belonged to the order Poduromorpha (31%). The length of the Acari collected
ranged from 0.6 to 0.9 mm, whereas Collembola were 1.3–1.5 mm in length. The
litter layer at the Nagano sampling site had the highest average weight, and
mesofaunal abundance was also highest at this site (Fig. 3.8). The number of
individuals was correlated to the average weight of the litter layer, and as litter
weight increased, the abundance of both Acari and Collembola tended to increase.
The mean abundance of Acari and Collembola in this study, conducted in temperate
deciduous forests, translates to a density of 11,043 individuals/m
2 and 10,774
individuals/m
2 , respectively. These values are lower than those reported for most
temperate areas of central Japan (Hijii 1994) and some tropical sites (e.g., Seastedt
1984; Gonzalez et al. 2001). At the Chokai and Iwaki sites, Acari were more
abundant. Greater abundance of Acari than Collembola in forests of central Japan
has been reported previously, and the authors proposed this trend was related to the
heavy rainfall, acidic soil, large amount of litter accumulation, and slow decomposition rate (Takeda and Abe 2001; Lin et al. 2002). At the Akita and Nagano sites,
Acari were less abundant than Collembola, in accordance with the findings of Hijii
(1994), who reported on the ratio of springtails to mites in coniferous forests of
Japan. Using our estimates of the proportion of each type of mesofauna at each site,
we estimated the quantity of each fungal species consumed by each group in each
area, based on RFLP peak heights (Fig. 3.9). Not only did Acari and Collembola
predominate in abundance, but their intake of ectomycorrhizal fungi was highest
among all groups of mesofauna. This result shows that Acari and Collembola play a
major role in the regulation of ectomycorrhizal fungi in forest soils.
We also investigated whether the fungal communities extracted from Acari and
Collembola significantly differed from those extracted from other soil mesofauna.
Figure 3.10 shows the results of R-analysis with a stress value of 0.0078, suggesting
42
A. Amasya and K. Narisawa