Research Projects -
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森林草原生態系の一体的管理を目指す：森林に遺された過去の草原性種子からの挑戦
Grant number：22H03797 2022.04 - 2026.03
日本学術振興会 科学研究費助成事業 基盤研究(B)
小山 明日香, 兵藤 不二夫, 山本 節子, 内田 圭
Grant amount：\17030000 （ Direct expense: \13100000 、 Indirect expense：\3930000 ）
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ミミズの土壌肥沃度改善機能の活用に向けてー圃場実証と機能の定量化ー
Grant number：21H02335 2021.04 - 2026.03
日本学術振興会 科学研究費助成事業 基盤研究(B) 基盤研究(B)
金田 哲, 池田 紘士, 米村 正一郎, 兵藤 不二夫, 舟山 健, 和穎 朗太, 伊藤 通浩, 上野 秀人
Grant amount：\17290000 （ Direct expense: \13300000 、 Indirect expense：\3990000 ）
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鳥類標本の羽から探る生態と種分化
Grant number：21H00622 2021.04 - 2026.03
日本学術振興会 科学研究費助成事業 基盤研究(B) 基盤研究(B)
武山 智博, 小高 信彦, 水田 拓, 岩見 恭子, 富田 直樹, 兵藤 不二夫
Grant amount：\17160000 （ Direct expense: \13200000 、 Indirect expense：\3960000 ）
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Role of soil microbial function and diversity on determining soil fertility along a topographic gradient
Grant number：21H02235 2021.04 - 2025.03
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B) Grant-in-Aid for Scientific Research (B)
舘野 隆之輔, 徳地 直子, 廣部 宗, 兵藤 不二夫, 磯部 一夫
Grant amount：\17160000 （ Direct expense: \13200000 、 Indirect expense：\3960000 ）
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Spiders eat insects - but Why are ant-mimicking jumping spiders vegetarian?
Grant number：21K06310 2021.04 - 2024.03
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C) Grant-in-Aid for Scientific Research (C)
橋本 佳明, 市岡 孝朗, 兵藤 不二夫, 山崎 健史
Grant amount：\4290000 （ Direct expense: \3300000 、 Indirect expense：\990000 ）
当初は，台湾での海外調査を計画をしていたが，コロナ禍で実施できなかった為、R4年度にこれらを実施する予定
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Transition process of seagrass-seaweed meadows driven by water and material transport from watersheds: Toward quantification and utilization of the ecosystem services
Grant number：21H03650 2021.04 - 2024.03
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B) Grant-in-Aid for Scientific Research (B)
齋藤 光代, 濱田 麻友子, 兵藤 不二夫, 小野寺 真一, 作野 裕司
Grant amount：\17290000 （ Direct expense: \13300000 、 Indirect expense：\3990000 ）
本研究では，多様な生態系サービス機能を有する沿岸藻場の分布や藻場生態系の多様性変遷過程について，特に流域の水・物質輸送の影響に着目し明らかにすることを目的とし，初年度であるR3年度は以下のとおり実施した．
(1)河川水・地下水流出にともなう物質輸送量評価：1)流域水・物質輸送評価：①沿岸域に藻場が分布する瀬戸内海の島嶼（広島県生口島）を対象に，島内の流域において河川流量および地下水位のモニタリングを実施した．②対象流域に水・物質輸送モデル（Soil & Water Assessment Tool: SWAT）を適用・構築する準備を行った．2)SGD物質輸送評価：①対象流域沿岸の藻場分布域において，海底湧水（SGD）のトレーサーとなる塩分，水温，ラドン濃度，および栄養塩濃度の海水中の空間分布を確認するとともに，潮間帯にSGD観測用ピエゾメーターを設置し，同様に塩分，水温，ラドンおよび栄養塩濃度のモニタリングを実施した．
(2)藻場と構成種の空間分布・時間変化の把握：①ドローンを用いて対象流域沿岸の藻場の空撮を実施し，取得した画像データの解析から藻場とその構成種の空間分布を明らかにした．②現地での踏査調査（海草・海藻類の分布密度，種類，固体サイズなどの測定）を実施し，それらに基づき①の結果の検証を行った．
(3)藻場生態系の食物連鎖構造および栄養塩循環の解明：1)食物連鎖構造解析：①対象流域の藻場分布域において河川水・地下水および海水，堆積物試料，藻場を構成する海草・海藻類のサンプリングを実施し，窒素・炭素安定同位体比を測定した．2)栄養塩循環評価：①藻場分布域でのクロロフィルaと濁度の測定，および水試料の採取と栄養塩分析を行った．
(4)藻場生態系の生物多様性評価：①対象流域の藻場分布域において海水および堆積物試料を採取し，環境DNAの分析を行った． -
Effects of soil environments on responses of ecosystem functions of Collembola communities against to global warming
Grant number：19K06126 2019.04 - 2022.03
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C) Grant-in-Aid for Scientific Research (C)
菱 拓雄, 兵藤 不二夫
Grant amount：\4420000 （ Direct expense: \3400000 、 Indirect expense：\1020000 ）
土壌生物群集の構造と機能に、長期的な環境条件としての立地条件と、温暖化実験処理の影響がどのように影響するのかについて明らかにする調査を行った。これまで、温暖化の実験の多くは生物群集のそれまで経た環境の経験の影響（レガシーエフェクト）を無視したものが多かった。本研究では近年着目されているレガシーエフェクトにより、立地条件によって土壌性トビムシ群集構造の種構成や機能形質が異なる方向の影響を受けることを明らかにしており、土壌動物群集の機能形質が、山地地形によるレガシーエフェクトの影響を強く受けていることを示す証拠が得られた。
成果公表として、今年度は温暖化に深く関係する自然の環境傾度である標高と、季節変動が、トビムシ群集の種、個体形質に強く影響し、特に強いストレスがかかる冬にのみ形質選択が生じ、それ以外の季節には標高による形質選択が生じないという形質選択の季節依存性を見出したという発見について国際学会で発表を行った（ICSZイタリア、オンライン）。また、日本で現在消失している下層植生の密度が土壌の安定性を増加させるプロセスをトビムシ群集から説明できることを示す研究成果を国際学会で発表した（ICA、イタリア、オンライン）。また、標高傾度や、日本の気候傾度に沿ってトビムシ群集の形質値がどのように変化するのかについても国内学会（日本土壌動物学会、日本生態学会）で発表を行った。
また、この研究が前提としている斜面方位での土壌動物群集の違いについて、査読付き学術専門誌上で英語論文を公表済みである。
本研究課題での実験結果は充分に意義あるものであり、関連する研究結果の公表は十分に行っている状況である。したがって当該年度の実績は順調に進捗しているといえる。 -
Ant-mimicking effects increase species diversity in Myrmarachne spiders
Grant number：18K06386 2018.04 - 2021.03
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
Hashimoto Yoshiaki
Grant amount：\4290000 （ Direct expense: \3300000 、 Indirect expense：\990000 ）
The precise ant mimicry of Myrmarachne jumping spiders (Salticidae) has been attributed to their high defensive effectiveness against predators. In this study, we found that the ant mimicry of Myrmarachne spiders reduces their ability to capture prey and shifts their diet to a plant-based source, and that the spider species have the habit of remaining close to their mimetic model ant species, which indicates the possibility of the spider using the nectar glands and other food sources monopolized by the mimetic model ant species in their territory. Furthermore, our DNA phylogenetic analysis revealed that speciation to the same mimetic model ant species occurs repeatedly in different phylogenetic lineages of Myrmarachne jumping spiders. These findings suggest that ant mimicry in Myrmarachne jumping spiders is a strategy for coexistence with mimetic model ants and a mechanism for creating species diversity in the spider genus.
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Plant-soil feedbacks in a forest ecosystem governed by functional traits of tree species
Grant number：17H03736 2017.04 - 2021.03
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
KUROKAWA HIROKO
Grant amount：\17550000 （ Direct expense: \13500000 、 Indirect expense：\4050000 ）
This study aimed to examine the role of plant-soil feedback in tree community assembly and multi-species coexistence mechanism using a trait-based approach. In a 1.2-ha study plot in the Ogawa Forest Reserve (Ibaraki), where population dynamic data and functional traits of adult and juvenile trees on all coexisting tree species have been accumulated, trait data of current-year seedlings and seedlings older than one year were newly collected. In addition, soil biotic and abiotic properties were measured at 10m x 10m grid points within the study area to develop the spatial data on soil properties. This allowed us to analyze the relationship between plant functional traits and population dynamics across growth stages and to analyze the determinants of soil properties. We found that soil properties are influenced by the community-weighted mean of some functional traits of above-ground trees and litter pool on the forest floor.
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同位体から昆虫の機能形質を評価する
Grant number：17H01912 2017.04 - 2021.03
日本学術振興会 科学研究費助成事業 基盤研究(B) 基盤研究(B)
兵藤 不二夫, 菱 拓雄, 黒川 紘子, 岸本 圭子
Grant amount：\16900000 （ Direct expense: \13000000 、 Indirect expense：\3900000 ）
地球規模で生じている生物の種構成の変化が，生態系機能に及ぼす影響を明らかにすることは環境学の重要な課題である．現在，植物群集の種ごとの機能形質をもとに，その生態系機能を評価する研究が広く行われている．一方，多様な表現型を持つ昆虫など動物については，共通の機能形質を測定することが困難なため，そのような研究はほとんどない．本研究では，動物の食性を反映する同位体を用いて，昆虫の生態系機能に関連する形質を評価することを目的としている。本年度はまず調査方法の確立を行い、その後、当初予定していたモニタリング1000の3サイト（半田山（岡山県）、椎葉（宮崎県）、小佐渡（新潟県））において6月と9月の2度にわたりアリ類、トビムシ類、糞虫類や土壌有機物（リターと土壌）の採集を行った。昆虫試料については、個体数の計測や同定、同位体分析用試料の作成を行った。土壌試料については栄養塩の測定等、土壌特性の評価を行った。その結果、これら3地点での昆虫群集組成の違いや調査地ごとの特性が把握できた。昆虫試料の一部については連続フロー型同位体比質量分析計を用いて炭素、窒素同位体分析を行った。また、放射性炭素濃度については、封管法により昆虫試料から二酸化炭素を生成、グラファイトを作成し、加速器質量分析計によって放射性炭素分析を行った。また、一部の昆虫については形態計測を行い、外部形態に基づく形質評価も行った。現在、これら得られたデータの解析中である。
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Effects of environmental farming system on soil function of earthworm
Grant number：16H05058 2016.04 - 2020.03
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
KANEDA Satoshi
Grant amount：\17030000 （ Direct expense: \13100000 、 Indirect expense：\3930000 ）
The objective of this study are estimation of variation of earthworm soil aggregate formation and earthworm density by environmental farming system like weed cover mulching and organic farming. In this study, life-forms of earthworm were classified, and earthworm community were investigated in orchard of weed cover mulching and organic farming. Relationship between soil parameters and soil aggregate formation rate by earthworm were studied. Seventeen species life-forms could be classified. Weed cover mulching enhanced density of epigeic species. There was no relationship between soil properties and soil aggregation formation rate. Therefore, previous studies results, relationship between soil aggregate formation rate and soil moisture, temperature and worm weight applied to field survey. According to the estimation, organic farming enhanced soil aggregate formation rate.
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Ecological study of the African great apes under human disturbance
Grant number：16H02753 2016.04 - 2019.03
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
Yumoto Takakazu
Grant amount：\36530000 （ Direct expense: \28100000 、 Indirect expense：\8430000 ）
The research was conducted on Western gorillas in the Gabonese Republic, bonobos in the Democratic Republic of Congo, and chimpanzees in Republic of Uganda, under the human-dominant landscape, mainly for their habitat uses and food selections. These African great apes are regarded as representatives of the primeval tropical forests. However, in reality, they depend largely on the fruits and leaves of pioneer plants or terrestrial herbs which are characteristic of secondary forests. The functional traits of the leaves of the tree species were examined, and we found that tree species in the secondary forest have the higher protein and the lower tannin content than those in the primary forest. These functional traits of the leaves are the desirable properties as a food of wild primates.
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Evaluation of stability of a tropical rainforest food web through isotope anlayses
Grant number：16K14811 2016.04 - 2019.03
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research Grant-in-Aid for Challenging Exploratory Research
Fujio Hyodo, Itioka Takao
Grant amount：\3640000 （ Direct expense: \2800000 、 Indirect expense：\840000 ）
Tropical rainforests are one of the ecosystems that have highest biodiversity, and the food webs have long been considered to be stable. However, the stability of the tropical rainforest food webs is poorly investigated because of the technical difficulty. In this study, we applied stable carbon and nitrogen isotopes of bulk samples, nitrogen isotopes of amino acids, and radiocarbon to investigate the feeding habits of Hymenopterans sampled in a tropical rainforest. Our results showed that there was no clear difference in their feeding habits during seven years, supporting the view on the stability of tropical rainforest food webs.
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Grant number：16H02947 2016.04 - 2019.03
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B) Grant-in-Aid for Scientific Research (B)
AITA Maki, YAMAGUCHI Atsushi
Grant amount：\18200000 （ Direct expense: \14000000 、 Indirect expense：\4200000 ）
We analyzed carbon and nitrogen stable isotope ratios of zooplankton from the sub-arctic to tropical western North Pacific and the Chukchi Sea. Our results clearly showed that a similar regularity between the food chain and the N / C isotope ratio, regardless structure of the food web and biological species. Isotopic analysis of meso-zooplankton community in the Kuroshio current region suggested that the offshore area use energy sources derived from regenerative nutrient and nitrogen fixation. In addition, the isotopic ratios of the community of diatoms, cyanobacteria and juvenile fish, large phytoplankton is minor as a trophic source of meso-zooplankton community in the Kuroshio and major prey items of fish larvae are small copepods.
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Detect the vulnerable area for N saturation based on new concept of N saturation
Grant number：15H04515 2015.04 - 2019.03
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B) Grant-in-Aid for Scientific Research (B)
Tokuchi Naoko, Koba Keisuke, Ohte Nobuhito
Grant amount：\16250000 （ Direct expense: \12500000 、 Indirect expense：\3750000 ）
The stream water data with high NO3 concentration and high NO3-O isotope ratio was analyzed by GIS and random forest. In GIS we prepared the data; vegetation, climate, N deposition etc. Using random forest the high contributed factor was chosen.
It results that the N saturation is caused by N deposition, especially N deposition during the growing season. -
Grant number：15H05113 2015.04 - 2019.03
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B) Grant-in-Aid for Scientific Research (B)
TATENO Ryunosuke, TATSUMI Chikae, DU Sheng, SHI Weiyu
Grant amount：\17030000 （ Direct expense: \13100000 、 Indirect expense：\3930000 ）
This study aimed to investigate the how semi-arid ecosystems change in response to precipitation variations under future climate change by focusing on soil nitrogen dynamics and soil microbes. In this study, we conducted several experiments such as the field survey along the precipitation gradient, the small plot scale rainfall manipulation experiment, the in-situ soil exchange incubation experiment, and the moisture manipulation laboratory soil incubation experiment on semi-arid forests near arid boundary on the Loess Plateau, China. In this study, we revealed the responses in soil nitrogen dynamics and soil microbial communities to short- and long-term changes in precipitation and soil moisture on semi-arid ecosystems.
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Study on host preference of parasitoid Diptera with stable isotope analysis and In vitro experiment
Grant number：26440220 2014.04 - 2017.03
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C) Grant-in-Aid for Scientific Research (C)
TACHI TAKUJI, NAKAMURA Satoshi
Grant amount：\4940000 （ Direct expense: \3800000 、 Indirect expense：\1140000 ）
Tachinid flies are endoparasitoid of other insects and arthropods, and their larvae feed on the host body. We study information on hosts of the tachinid larvae with carbon and nitrogen isotope analysis for adults and In vitro experiment for larvae. In the isotope analysis, the data can roughly distinguish parasitoids from the other feeding habits such as saprophagy and organic decomposers. In particular, the saprophagous flies are usually very high in the nitrogen isotope ratio. However, there are individual and geographical variations in these isotope data and these variations grow with high trophic level. In the breeding experiments, isotope fractionation is confirmed to occur in insect metamorphosis and biological interactions. The interactions of this study are between plants (artificial diet)-phytophagous insects (hosts)- predator (parasitoids). Artificial medium with body fluid of host species (Mythimna separate) is developed for a tachinid species, Exorista japonica.
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Grant number：25304003 2013.04 - 2017.03
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B) Grant-in-Aid for Scientific Research (B)
ISHII Reiichiro
Grant amount：\13130000 （ Direct expense: \10100000 、 Indirect expense：\3030000 ）
Field observation in Mongolian forest-steppe transition zone and analysis of its soil organic components were conducted to obtain feasible quantitative parameters for vegetation transition model. We clarified following quantitative features for the interactions between the two vegetation types and between vegetation development and soil formation: 1) Forest vegetation has been present there at least for 150 years while the soil organic matters aged 600-800 years in grass-covered area and about 6500 years in forest stand, which could provide quantitative parameters for time-scale of the vegetation transition; 2) Soil organic matters sampled from either vegetation types not always exhibit clear identity of the current vegetation type, from which we could expect that several vegetation transitions might have been occurred in the thousands years' past possibly induced by human activity or forest fire.
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Comparison of Primate Communities Including Great Apes and Forest Structure
Grant number：25257407 2013.04 - 2016.03
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A) Grant-in-Aid for Scientific Research (A)
Yumoto Takakazu
Grant amount：\40690000 （ Direct expense: \31300000 、 Indirect expense：\9390000 ）
The political and social situation of the target site, Danam Valley in Sabah Malaysia has not improved, so that we changed the site into Kinabatamgan in Sabah, Malaysia. We obtained study permission as well as export plant specimen, and did a survey. As a results of the research project, we obtained behavioral and ecological data on gorillas, chimpanzees, bonobos, and orangutans as well as data on vegetation and plant functional characteristics of main components.
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Radiocarbon reveals residence time of carbon driving belowground food webs
Grant number：25840158 2013.04 - 2016.03
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B) Grant-in-Aid for Young Scientists (B)
Hyodo Fujio
Grant amount：\4420000 （ Direct expense: \3400000 、 Indirect expense：\1020000 ）
The goal of this study is to explore the diet ages of consumers in three forest ecosystems with different climates. The estimation of diet age can be performed by using natural abundance of radiocarbon. The results showed that diet ages of soil invertebrates did not differ among the studies sites, despite great difference in soil properties, such as soil respiration and radiocarbon concentrations.
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Designing soil food web strucute for sustainable plant production
Grant number：25281053 2013.04 - 2016.03
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B) Grant-in-Aid for Scientific Research (B)
Kaneko Nobuhiro, NAKAMORI Taizo, HIURA Tsutom, KOMATSUZAKI Masakazu, SHIMANO Satoshi, HYODO Fujio, KARASAWA Shigenori
Grant amount：\18070000 （ Direct expense: \13900000 、 Indirect expense：\4170000 ）
The effects of land management on soil food web structure and its effects on soil nutrient cycling were studied to enable sustainable land use. Biodiversity data in Japan was reviewed. After clear cut of forest, decomposition of soil organic matter has been promoted and this effect continued for long-term. Under no-tillage weed mulch cover management, nitrogen mineralization potential, biomass of soil microbes and fauna were higher than tillage treatment, Biomass of AM mycorrhiza was especially higher in no-tillage. Reducing soil disturbance can maintain soil food web structure with higher biomass in all trophic level, and this change can succefully support plant growth.
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Grant number：24570109 2012.04 - 2015.03
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C) Grant-in-Aid for Scientific Research (C)
HASHIMOTO Yoshiaki, ITIOKA Takao, ENDO Tomoji, HYODO Fujio
Grant amount：\5590000 （ Direct expense: \4300000 、 Indirect expense：\1290000 ）
Ant-mimic spiders mainly occur in the tropical regions. Since ant diversity is especially high in the tropics, it seems that the remarkable diversity of ant-mimic spiders in tropics is associated with the diversity of ants. To assess this assumption, the present study examined how ant biodiversity reflects on biodiversity of the mimic spiders in tropical forests. Using morphometric tools to analyze objectively visual resemblance between them, we can detect supporting evidence that diverse patterns of ant-mimic spiders were closely associated with diversity patterns of sympatric ants. Furthermore, using stable isotope analysis and experiment of predation, we can also find mimetic association of ant-mimic spiders to ant models affects their foraging behavior, which may function as food segregations among them. These results indicate that ant-mimicry may play as a mechanism of creating species diversity and promoting coexistence of multiple species in tropical forests.
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Grant number：22370011 2010 - 2012
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B) Grant-in-Aid for Scientific Research (B)
TAYASU Ichiro, UCHIDA Masao, HYODO Fujio
Grant amount：\18720000 （ Direct expense: \14400000 、 Indirect expense：\4320000 ）
We have done a watershed-level study of the relationship between carbon cycling and ecosystem structure using the measurement of carbon-14 concentrations (Δ^14C value) and nitrogen isotope ratios of individual amino acids. Δ^14C value indicated that carbon source of river food web was both sequestered carbon from watershed and ambient CO_2. The contribution of both pathways depended on the relative importance of algal production (in-stream production) and terrestrial litter input.
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Changes in plant nitrogen sources during boreal forest succession
Grant number：22770020 2010 - 2011
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B) Grant-in-Aid for Young Scientists (B)
HYODO Fujio
Grant amount：\3510000 （ Direct expense: \2700000 、 Indirect expense：\810000 ）
To examine whether plants change nitrogen sources during boreal forest succession, I measured nitrogen isotopic signatures of plants and soil nitrogen across two chronosequences of time frame of approximately 400 years and 5000 years in northern Sweden. I found that the nitrogen isotopic signatures significantly changed along the forest succession. Based on the preliminary results on nitrogen isotope ratios of dissolved nitrogen sources in soil, these results suggest that the importance of dissolved organic nitrogen, biological nitrogen fixation by mosses, and nitrogen derived from mycorrhizal fungi as plant nitrogen source change along the forest succession.
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生体構成有機物の年令からみた陸上生態系の食物網の構造
Grant number：03J09346 2003 - 2005
日本学術振興会 科学研究費助成事業 特別研究員奨励費 特別研究員奨励費
兵藤 不二夫
Grant amount：\3700000 （ Direct expense: \3700000 ）
二酸化炭素の形で大気中にある放射性炭素(^<14>CO_2)は宇宙線の作用による上空での生成と放射性崩壊(半減期:5730年)による消失のバランスにより、大気中ではおおよそ一定量に保たれている。しかし、^<14>Cは冷戦期の核実験によって大量に作られ、その後1963年の核実験禁止条約の締結後、急激に減少している。本研究では、その核実験によって大量に作られた^<14>Cをトレーサーとして用いて、陸上食物網の構造に時間軸を導入することを目的としている。すなわち、大気14Cは光合成によって植物に取り込まれ、その年々の減少は植物の一次生産物にも反映されている。よって、これまでの既知の大気14Cの記録と消費者の体の^<14>C含量を測定し比較することで何年前に作られた一次生産物であるをその消費者は利用しているかが明らかになる。
従来の食物網の研究では一次生産から消費者へとつながる様々な量の物質やエネルギーの流れを対象としていたが、それらの流れには別の軸、すなわち時間軸が存在することはあまり考慮されていなかった。そこでの時間軸とは、植物が大気中の二酸化炭素を固定してから、その一次生産物が消費者によって利用されるまでの時間である。私はこの時間軸のことを食物年齢(diet age)と定義した。
本研究では熱帯生態系の重要な分解者であるシロアリを対象にその食物年齢を上述の14C分析から推定した。その結果、シロアリの食物年齢は7年から50年という幅をもつこと、また土壌食シロアリでは7-13年、木材食シロアリでは12-18年などその食性に応じた値を持つことが明らかとなった。また熱帯雨林の主要な送粉者であるハリナシバチ、ミツバチの14C含量を測定したところ、ハリナシバチでは2-4年、ミツバチでは0年と同じ生食食物網に属する生物間でも、食物年齢が異なることが明らかとなった。 -
キノコシロアリ亜科におけるキノコ栽培の進化
Grant number：00J03013 2000 - 2001
日本学術振興会 科学研究費助成事業 特別研究員奨励費 特別研究員奨励費
兵藤 不二夫
Grant amount：\2000000 （ Direct expense: \2000000 ）