研究者詳細 - 兵藤　不二夫

論文 - 兵藤　不二夫

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A new species of the genus Sphecotypus O. Pickard-Cambridge, 1895 from Borneo, with a comparison with the holotype of S. birmanicus (Thorell, 1897) (Araneae, Corinnidae) 査読

Yamasaki, T, Hashimoto, Y, Endo, T, Hyodo, F, Itioka, T, Tavano, M

Annali del Museo Civico di Storia Naturale Giacomo Doria 110 21 - 32 2017年

Homogeneous diet of contemporary Japanese inferred from stable isotope ratios of hair

Soichiro Kusaka, Eriko Ishimaru, Fujio Hyodo, Takashi Gakuhari, Minoru Yoneda, Takakazu Yumoto, Ichiro Tayasu

SCIENTIFIC REPORTS 6 2016年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：NATURE PUBLISHING GROUP

The globalization of food production and distribution has homogenized human dietary patterns irrespective of geography, but it is uncertain how far this homogenization has progressed. This study investigated the carbon and nitrogen isotope ratios in the scalp hair of 1305 contemporary Japanese and found values of -19.4 +/- 0.6% and 9.4 +/- 0.6% (mean +/- SD), respectively. Within Japan, the inter-regional differences for both isotope ratios was less than 1%, which indicates low dietary heterogeneity among prefectural divisions. The carbon and nitrogen isotope ratios of the hair showed a significant correlation with the results of questionnaires on self-reported dietary habits. The carbon isotope ratios from Japan were lower than those in samples from the USA but higher than those in samples from Europe. These differences stem from the varying dietary proportions of food products originally derived from C-3 and C-4 plants. The dietary variation of Japan is as small as those of Europe and USA and smaller than those of some Asian countries. These results indicate that dietary homogeneity has progressed in Japan, which may indicate the influence from the spread of the Western-style diet and food globalization, although dietary heterogeneity among countries is still preserved.

DOI： 10.1038/srep33122

Effects of remnant primary forests on feeding habits of ants in a secondary forest in Sarawak, Malaysia: An isotopic study

Fujio Hyodo, Keiko Kishimoto-Yamada, Masayuki Matsuoka, Hiroshi O. Tanaka, Yoshiaki Hashimoto, Reiichiro Ishii, Takao Itioka

Food Webs 6 48 - 54 2016年3月

Carbon and nitrogen isotopes reveal feeding habits of arthropods in tropical rain forests

Fujio Hyodo

Japanese Journal of Ecology 66 ( 2 ) 421 - 428 2016年1月

A new species of the genus Castoponera (Araneae, Corinnidae) from Sarawak, Borneo, with comparison to a related species

Takeshi Yamasaki, Yoshiaki Hashimoto, Tomoji Endo, Fujio Hyodo, Takao Itioka

ZOOKEYS 2016 ( 596 ) 13 - 25 2016年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PENSOFT PUBL

A new species of the genus Castoponera Deeleman-Reinhold, 2001, Castoponera christae sp. n., is described here. The species is closely related to C. lecythus Deeleman-Reinhold, 2001, but can be distinguished by the structures of the male palp and the female genitalia.

DOI： 10.3897/zookeys.596.8525

Changes in aboveground and belowground properties during secondary natural succession of a cool-temperate forest in Japan

Hyodo, F., Haraguchi, T.F., Hirobe, M., Tateno, R.

Journal of Forest Research 21 ( 4 ) 170 - 177 2016年

Pattern of co-occurrence between ant-mimicking jumping spiders and sympatric ants in a Bornean tropical rainforest

Yoshiaki Hashimoto, Tomoji Endo, Takao Itioka, Fujio Hyodo, Takashi Yamasaki, Maryati Mohamed

RAFFLES BULLETIN OF ZOOLOGY 64 70 - 75 2016年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：NATL UNIV SINGAPORE, SCHOOL BIOLOGICAL SCIENCES

To evaluate the pattern of co-occurrence between ant-mimicking jumping spiders and sympatric ants in a tropical rainforest, we sampled these arthropods and also non-mimicking jumping spiders by net-sweeping from the understory vegetation in Sabah, Malaysian Borneo. We collected the spiders and ants from a total of 594 sample points, with ants occurring in 445 points (79.4%), non-mimicking jumping spiders in 308 (51.9%), Agorius ant-mimicking spiders in 40 (6.7%), and Myrmarachne ant-mimicking spiders in 59 (9.9%). Frequencies of occurrence of non-mimicking jumping spiders showed no significant difference in relation to ant-occurrence, whereas both of the ant-mimicking spider genera occurred significantly more frequently with ants. Agorius spiders co-occurred with a wider variety of different ant genera, compared to Myrmarachne, but logistic regression analyses and a null model test showed no specific associations between Agorius spiders and the sympatric ant genera. The mimetic resemblances of Agorius spiders are considered to be much less ant-like than those of Myrmarachne spiders, because their constriction of the cephalothorax is not as obvious as in Myrmarachne. These data provide support for the multi-model hypothesis (Edmunds 2000), which predicted that a poor ant-mimic should occur in ranges of many different ants, compared to good ant-mimic.

Use of stable carbon and nitrogen isotopes in insect trophic ecology

Fujio Hyodo

ENTOMOLOGICAL SCIENCE 18 ( 3 ) 295 - 312 2015年7月

記述言語：英語出版者・発行元：WILEY-BLACKWELL

Insects are the most diverse organisms and often the most abundant animals in some ecosystems. Despite the importance of their functional roles and of the knowledge for conservation, the trophic ecology of many insect species is not fully understood. In this review, I present how stable carbon (C) and nitrogen (N) isotopes have been used to reveal the trophic ecology of insects over the last 30years. The isotopic studies on insects have used differences in C isotope ratios between C-3 and C-4 plants, along vertical profiles of temperate and tropical forest stands, and between terrestrial and aquatic resources. These differences enable exploration of the relative importance of the food resources, as well as movement and dispersal of insects across habitats. The C-13-enrichment (approximately 3 parts per thousand) caused by saprotrophic fungi can allow the estimation of the importance of fungi in insect diets. Stable N isotopes have revealed food resource partitioning across diverse insect species above and belowground. Detritivorous insects often show a large trophic enrichment in C-13 (up to 3 parts per thousand) and N-15 (up to 10 parts per thousand) relative to the food substrates, soil organic matter. These values are greater than those commonly used for estimation of trophic level. This enrichment likely reflects the prevalence of soil microbial processes, such as fungal development and humification, influencing the isotopic signatures of diets in detritivores. Isotope analysis can become an essential tool in the exploration of insect trophic ecology in terms of biogeochemical C and N cycles, including trophic interactions, plant physiological and soil microbial processes.

DOI： 10.1111/ens.12128

Dependence of diverse consumers on detritus in a tropical rain forest food web as revealed by radiocarbon analysis

Fujio Hyodo, Takashi Matsumoto, Yoko Takematsu, Takao Itioka

FUNCTIONAL ECOLOGY 29 ( 3 ) 423 - 429 2015年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：WILEY-BLACKWELL

Energy and material flows from dead organic matter, or detritus, to generalist predators have a potential impact on the food web dynamics. However, little is known about how commonly generalist predators depend on detritivorous prey, or the detritus on which the detritivores have fed in terrestrial food webs. To examine this, we measured the diet ages of terrestrial invertebrate and vertebrate consumers (>30 species) at multiple trophic levels in a tropical rain forest, with a particular focus on ants and termites by using radiocarbon (C-14). Here, we defined diet age as the lag time between the primary production and the utilization by consumer organisms. The diet ages varied from 0 to >50years and corresponded to known feeding habits of the consumers. Herbivores such as bees, butterflies, a frugivorous bird and bat, and nectar-feeding ants had young diet ages (0-3years). Meanwhile, detritivores such as termites had old diet ages, which increased according to the food resources in the order of litter (6years), soil (10years) and wood (19years). The diet ages of predators such as wolf spiders, hunting wasps, army ants, tree shrews and an insectivorous bat were intermediate (2-8years), indicating the dependence of many predators on detritivores. Because known dietary components of the predators include herbivores and detritivores, the intermediate ages likely indicate the coupling of energy and material flows between plant-based and detritus-based food webs. Diet ages of soil-feeding termite and army ant differed significantly, although a previous study reported that their nitrogen isotope ratios were indistinguishable despite the differing feeding habits. This indicates that radiocarbon can distinguish the two factors, trophic enrichment and the below-ground processes (humification), both of which could influence the nitrogen isotopic signatures of the terrestrial consumers. Our results show that radiocarbon would provide insights into structures of terrestrial food webs as well as time frame of energy and material flows through the webs.

DOI： 10.1111/1365-2435.12357

Faunal studies of sap beetles (Coleoptera: Nitidulidae) in primary and secondary tropical rainforests in the middle reaches of the Baram River Basin, Borneo.

J. Yoshimoto, S. T. Hisamatsu, K. Kishimoto-Yamada, F. Hyodo, Y. Hashimoto, T. Itioka

Contributions from the Biological Laboratory Kyoto University 30 ( 2 ) 77 - 84 2015年

記述言語：英語掲載種別：研究論文（大学，研究機関等紀要）出版者・発行元：京都大学大学院人間・環境学研究科

This study presents a species inventory of sap beetles (Coleoptera: Nitidulidae), together with descriptions of their habitat types, in lowland tropical rainforests in the middle reaches of the Baram River Basin, Borneo (Sarawak, Malaysia). Thirty-two nitidulid species belonging to 14 genera from six subfamilies were collected by banana-baited traps. There was no significant difference in species richness, abundance, diversity, or species composition between the primary and secondary forests, with 13 species being shared.

A new genus and species of myrmecophilous brentid beetle (Coleoptera: Brentidae) inhabiting the myrmecophytic epiphytes in the Bornean rainforest canopy

Munetoshi Maruyama, Luca Bartolozzi, Yoko Inui, Hiroshi O. Tanaka, Fujio Hyodo, Usun Shimizu-Kaya, Yoko Takematsu, Takuo Hishi, Takao Itioka

ZOOTAXA 3786 ( 1 ) 73 - 78 2014年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：MAGNOLIA PRESS

Pycnotarsobrentus inuiae Maruyama & Bartolozzi, gen. nov. and sp. nov. (Brentinae: Eremoxenini) is described from the Lambir Hills National Park, Borneo (Sarawak, Malaysia) based on specimens collected from Crematogaster difformis F. Smith, 1857 ant nests in the myrmecophytic epiphytic ferns Platycerium crustacea Copel. and Lecanopteris ridleyi H. Christ. A second species of Pycnotarsobrentus is known from Malaysia but is represented by only one female and consequently not yet described pending discovery of a male. Pycnotarsobrentus belongs to the tribe Eremoxenini and shares some character states with the African genus Pericordus Kolbe, 1883. No species of Eremoxenini with similar morphological modifications are known from the Oriental region.

DOI： 10.11646/zootaxa.3786.1.5

Use of carbon-13 and carbon-14 natural abundances for stream food web studies

Naoto F. Ishikawa, Fujio Hyodo, Ichiro Tayasu

Ecological Research 28 ( 5 ) 759 - 769 2013年9月

Changes in stable nitrogen and carbon isotope ratios of plants and soil across a boreal forest fire chronosequence

Fujio Hyodo, Soichiro Kusaka, David A. Wardle, Marie-Charlotte Nilsson

PLANT AND SOIL 367 ( 1-2 ) 111 - 119 2013年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SPRINGER

Nitrogen (N) and carbon (C) isotopic signatures (delta N-15 and delta C-13) serve as powerful tools for understanding temporal changes in ecosystem processes, but how these signatures change across boreal forest chronosequences is poorly understood.
The delta N-15, delta C-13, and C/N ratio of foliage of eight dominant plant species, including trees, understory shrubs, and a moss, as well as humus, were examined across a 361 years fire-driven chronosequence in boreal forest in northern Sweden.
The delta C-13 and C/N ratio of plants and humus increased along the chronosequence, suggesting increasing plant stress through N limitation. Despite increasing biological N fixation by cyanobacteria associated with feather mosses, delta N-15 showed an overall decline, and delta N-15 of the feather moss and associated vascular plants diverged over time from that of atmospheric N-2.
Across this chronosequence the N fixed by cyanobacteria is unlikely to be used by mosses and vascular plants without first undergoing mineralization and mycorrhizal transport, which would cause a change in delta N-15 signature due to isotopic fractionation. The decreasing trend of delta N-15 suggests that as the chronosequence proceeds, the plants may become more dependent on N transferred from mycorrhizal fungi or from N deposition.

DOI： 10.1007/s11104-013-1667-3

Effects of remnant primary forests on ant and dung beetle species diversity in a secondary forest in Sarawak, Malaysia

Keiko Kishimoto-Yamada, Fujio Hyodo, Masayuki Matsuoka, Yoshiaki Hashimoto, Masahiro Kon, Teruo Ochi, Seiki Yamane, Reiichiro Ishii, Takao Itioka

JOURNAL OF INSECT CONSERVATION 17 ( 3 ) 591 - 605 2013年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SPRINGER

Tropical landscape structures have been transformed into mosaic structures consisting of small patches of primary and secondary forests, and areas of other land use. Diversity of insect assemblages is often higher in primary forests than in surrounding secondary forests. However, little is known about how the primary forests affect diversity in surrounding secondary forests in a landscape. In Sarawak, Malaysia, the typical landscape in areas from which lowland tropical rainforests had originally spread consists mainly of primary and secondary forests, with small areas of cultivation. In this study, we examined how the proportion of remnant primary forests in a landscape affects species diversity and species composition of ants and dung beetles in Macaranga-dominated secondary forests. The proportions were quantified based on remote-sensing data at various spatial scales, ranging from 100- to 5,000-m radius from each of the target forests. We found that the proportions of remnant primary forests within a 100-m radius had a significant positive effect on ant species diversity, and those within 100-, 300-, and 500-m radii significantly affected species compositions. However, the proportions of remnant primary forests had no significant relationship with dung beetle diversity, while those within 100- and 1,000-m radii had significant effects on species composition. The different responses to the remnant primary forests are likely to be related to differences in the movement and dispersal traits between the two taxa.

DOI： 10.1007/s10841-012-9544-6

Possible ideas on carbon and nitrogen trophic fractionation of food chains: a new aspect of food-chain stable isotope analysis in Lake Biwa, Lake Baikal, and the Mongolian grasslands

Eitaro Wada, Reiichiro Ishii, Maki Noguchi Aita, Nanako O. Ogawa, Ayato Kohzu, Fujio Hyodo, Yoshihiro Yamada

ECOLOGICAL RESEARCH 28 ( 2 ) 173 - 181 2013年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SPRINGER JAPAN KK

Trophic fractionation of carbon and nitrogen isotopes (Delta delta C-13, Delta delta N-15) was examined using previously complied databases for food chains in Lake Biwa, Lake Baikal, and Mongolian grassland. The following two features were clarified: (1) For each ecosystem, the ratios of trophic fractionation of carbon and nitrogen isotopes (Delta delta N-15/Delta delta C-13) throughout food chain could be obtained as the slope of linear regression line on the delta N-15-delta C-13 plot. (2) Further, analysis of covariance (ANCOVA) revealed the slopes on delta N-15-delta C-13 were not significantly different among these various ecosystems and allowed us to have the regression by setting delta N-15 as the response variable: delta N-15 = 1.61 delta C-13 + [ecosystem specific constant] with standard errors of [+/- 0.41] and [+/- 9.7] for the slope and the intercept, respectively. It was suggested that the slope of the regression (or the ratio Delta delta N-15/Delta delta C-13) could be applicable to more complicated food webs in case nitrogen and carbon isotope ratios of primary producers can be assumed constant in space and time within the ecosystems. The results from simple linear regression analyses coincided well with the ANCOVA results for these ecosystems, although there was some discrepancy between the results of the two statistical analyses. Possible factors that govern the linear relationship between delta N-15 and delta C-13 along a food chain are discussed together with a new scope for the stable isotope food chain analyses.

DOI： 10.1007/s11284-012-1024-7

Changes in stable nitrogen and carbon isotope ratios of plants and soil across a boreal forest fire chronosequence

Fujio Hyodo, Soichiro Kusaka, David A. Wardle, Marie-Charlotte Nilsson

PLANT AND SOIL 364 ( 1-2 ) 315 - 323 2013年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SPRINGER

Nitrogen (N) and carbon (C) isotopic signatures (delta N-15 and delta C-13) serve as powerful tools for understanding temporal changes in ecosystem processes, but how these signatures change across boreal forest chronosequences is poorly understood.
The delta N-15, delta C-13, and C/N ratio of foliage of eight dominant plant species, including trees, understory shrubs, and a moss, as well as humus, were examined across a 361 years fire-driven chronosequence in boreal forest in northern Sweden.
The delta C-13 and C/N ratio of plants and humus increased along the chronosequence, suggesting increasing plant stress through N limitation. Despite increasing biological N fixation by cyanobacteria associated with feather mosses, delta N-15 showed an overall decline, and delta N-15 of the feather moss and associated vascular plants diverged over time from that of atmospheric N-2.
Across this chronosequence the N fixed by cyanobacteria is unlikely to be used by mosses and vascular plants without first undergoing mineralization and mycorrhizal transport, which would cause a change in delta N-15 signature due to isotopic fractionation. The decreasing trend of delta N-15 suggests that as the chronosequence proceeds, the plants may become more dependent on N transferred from mycorrhizal fungi or from N deposition.

DOI： 10.1007/s11104-012-1339-8

Use of radiocarbon to estimate diet ages of earthworms across different climate regions

Fujio Hyodo, Tomoko Uchida, Nobuhiro Kaneko, Ichiro Tayasu

APPLIED SOIL ECOLOGY 62 178 - 183 2012年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

Natural abundance of radiocarbon (C-14) has been applied to estimate the turnover time of soil carbon (C) across different climate regions. However, despite the important functional role played by soil animals in decomposition processes, little is known about variation in their C-14 concentrations across different climate regions. In this study, we measured C-14 concentrations of earthworms collected in three forests in Japan. In addition, we also reviewed C-14 data on earthworms that were previously reported. We used these data to test whether the diet ages (defined as time elapsed since C in the diet of earthworms was fixed from atmospheric CO2 by photosynthesis) differed according to feeding habits and across study sites in various climate regions ranging from cool temperate forest to tropical savanna. Multiple regression analysis showed that the diet ages of earthworms were significantly affected by both feeding habits and study sites. The diet ages of endogeic (soil-feeding) earthworms (8.3 +/- 0.4 years, mean SE) were significantly older than those of epigeic (litter-feeding) earthworms (2.6 +/- 0.5 years), with anecic (litter-/soil-feeding) earthworms (5.7 +/- 0.9 years) having intermediate diet ages. When mean diet age was compared for each feeding habit, only that of endogeic earthworms differed significantly across the sites. However, it did not necessarily become younger in warmer climate regions. These results either suggest that the degree of decomposition of soil organic matter used by earthworms differs among the study sites, or that the difference in the turnover time of Soil organic C used by earthworms across the sites is relatively small and variable due to factors other than temperature, such as soil texture and vegetation. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.apsoil.2012.09.014

Nitrogen niches revealed through species and functional group removal in a boreal shrub community

Michael J. Gundale, Fujio Hyodo, Marie-Charlotte Nilsson, David A. Wardle

ECOLOGY 93 ( 7 ) 1695 - 1706 2012年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：WILEY

Most theories attempting to explain the coexistence of species in local communities make fundamental assumptions regarding whether neighbors exhibit competitive, neutral, or positive resource-use interactions; however, few long-term data from naturally assembled plant communities exist to test these assumptions. We utilized a 13-year experiment consisting of factorial removal of three shrub species (Vaccinium myrtillus, V. vitis-idaea, and Empetrum hermaphroditum) and factorial removal of two functional groups (tree roots and feather mosses) to assess how neighbors affect N acquisition and growth of each of the three shrub species. The removal plots were established on each of 30 lake islands in northern Sweden that form a natural gradient of resource availability. We tested the hypotheses that: (1) the presence of functionally similar neighbors would reduce shrub N acquisition through competition for a shared N resource; (2) the removal of functional groups would affect shrub N acquisition by altering the breadth of their niches; and (3) soil fertility would influence the effects of neighbor removals. We found that the removal of functionally similar neighbors (i.e., other shrub species) usually resulted in higher biomass and biomass N, with the strength of these effects varying strongly with site fertility. Shrub species removals never resulted in altered stable N isotope ratios (delta N-15), suggesting that the niche breadth of the three shrubs was unaffected by the presence of neighboring shrub species. In the functional group removal experiment, we found positive effects of feather moss removal on V. myrtillus biomass and biomass N, and negative effects on E. hermaphrotium N concentration and V. vitis-idaea biomass and biomass N. Tree root removal also caused a significant shift in foliar delta N-15 of V. myrtillus and altered the delta N-15, biomass, and biomass N of E. hermaphroditum. Collectively, these results show that the resource acquisition and niche breadth of the three shrub species are often affected by neighbors, and further that both the identity of neighbors and site fertility strongly determine whether these interactions are positive, negative, or neutral. These findings have implications for understanding species coexistence and the reciprocal relationships between productivity and species diversity in this ecosystem.

DOI： 10.1890/11-1877.1

Variation in nitrogen isotopic composition in the Selenga river watershed, Mongolia

Fujio Hyodo, Junko Nishikawa, Ayato Kohzu, Noboru Fujita, Izuru Saizen, Jamsran Tsogtbaatar, Choijilsuren Javzan, Mangaa Enkhtuya, Davaadorj Gantomor, Narantsetsegiin Amartuvshin, Reiichiro Ishii, Eitaro Wada

LIMNOLOGY 13 ( 1 ) 155 - 161 2012年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SPRINGER JAPAN KK

The stable nitrogen (N) isotope ratio (delta N-15) has been used to examine the anthropogenic N input (i.e., septic water, wastewater, and manure) to aquatic ecosystems, because anthropogenic N generally has a delta N-15 signature distinct from that found in nature. Aquatic organisms and the derived organic matter such as sediments are reported to become increasingly enriched in N-15 as the human population density increases in watersheds. However, little is known about the relationship in steppe ecosystems, where the livestock population is greater than that of humans. Here, we conducted a preliminary study in the Selenga river mainstream watershed in Mongolia, which covers an area of approximately 300,000 km(2). A multiple regression analysis revealed that the delta N-15 of the riverine sediment was significantly affected by the human population density and more significantly by livestock population density. The population density, including both humans and livestock, significantly influenced delta N-15 of the macrophytic Potamogeton spp. The results showed that delta N-15 of riverine organic matter can be an indicator of the human and livestock population density, which is likely associated with the status of N cycles in livestock-dominated watersheds.

DOI： 10.1007/s10201-011-0351-7

琵琶湖湖底堆積物に記録された過去100年間のスギ花粉年間堆積量の変化

林竜馬, 兵藤不二夫, 占部城太郎, 高原光

日本花粉学会会誌 58 ( 1 ) 5 - 17 2012年

記述言語：日本語出版者・発行元：日本花粉学会

鉛-210とセシウム-137法による高精度の年代決定が行なわれた琵琶湖湖底堆積物の花粉分析によって,過去100年間のスギ花粉年間堆積量の変化を明らかにした.また,戦後の造林によるスギ人工林面積の増加と花粉飛散量との対応関係を検討するために,琵琶湖の近隣府県における31年生以上のスギ人工林面積の変化を推定し,琵琶湖湖底堆積物中のスギ花粉年間堆積量の変化との対比を行なった.花粉分析の結果,1900年以前ではスギ花粉年間堆積量が900〜1400grains・cm^<-2>・year^<-1>と比較的少なかったことが明らかになった.1900年以降になるとスギ花粉の年間堆積量が若干の増加傾向を示し,1920〜1970年頃には2800〜3700grains・cm^<-2>・year^<-1>の堆積量を示した.1970年頃以降になるとスギ花粉年間堆積量の増加が認められ,1970年代には4200〜4400grains・cm^<-2>・year^<-1>,1980年代前半には6300〜7100grains・cm^<-2>・year^<-1>に増加した.1980年代後半から1990年代にかけて,スギ花粉年間堆積量はさらに増加し,8300〜13400grains・cm^<-2>・year^<-1>に達した.このような琵琶湖湖底堆積物中のスギ花粉年間堆積量の増加は,31年生以上のスギ人工林面積の増加と同調したものであり,戦後の造林による成熟スギ人工林増加の影響を大きく受けて,多量のスギ花粉が飛散するようになったことを示している.また,琵琶湖湖底堆積物中のスギ花粉年間堆積量の推定値は,相模原市における大量飛散年の空中花粉量の経年変化との整合性も高く,これまで蓄積されてきた空中花粉調査のデータを補間し,より古い時期からの花粉飛散量変化の情報を提供しうるものと考えられる.さらに,琵琶湖堆積物の花粉分析結果を基にした地史的なスギ花粉年間堆積量との比較から,1980年代以降に増加したスギ花粉飛散量と同程度の飛散は3000〜2000年前頃ならびに最終間氷期の後半においても認められた.本研究では,鉛-210とセシウム-137法によって高精度での年代決定が行なわれた過去数100年間の堆積物についての花粉分析を行なうことにより,数10年から数100年スケールでの花粉堆積量変化の記録を復元できる可能性を示した.今後,各地で同様の研究を進めていくことにより,20世紀における全国的なスギ花粉飛散量の変化について明らかになることが期待される.

DOI： 10.24524/jjpal.58.1_5

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