Researcher Database

Junjiro Negishi
Faculty of Environmental Earth Science Integrated Environmental Science Conservation on Natural Environments
Associate Professor

Researcher Profile and Settings

Affiliation

  • Faculty of Environmental Earth Science Integrated Environmental Science Conservation on Natural Environments

Job Title

  • Associate Professor

J-Global ID

Research Interests

  • 底生動物   氾濫原   湧水   生息環境   河床低下   生態系保全   保全   水生生物   生態系管理   底性動物   流域管理   河川   生物多様性   流域保全   森林渓流生態系   生物濃縮   鳥類   放射性セシウム   農地生態系   森林農地生態系   放射性物質の移行   撹乱   有機物動態   森林生態系   放射性核種   食物網解析   渓流生態系   淡水魚類   河川生態系   河川流出   

Research Areas

  • Environmental science/Agricultural science / Biological resource conservation
  • Life sciences / Forest science
  • Environmental science/Agricultural science / Landscape science
  • Environmental science/Agricultural science / Environmental agriculture

Academic & Professional Experience

  • 2011 - 2013 Hokkaido University

Research Activities

Published Papers

  • Beverley C. Wemple, Trevor Browning, Alan D. Ziegler, Jorge Celi, Kwok Pan Sun Chun, Fernando Jaramillo, Nei K. Leite, Sorain J. Ramchunder, Junjiro N. Negishi, Ximena Palomeque, Derek Sawyer
    Ecohydrology 11 (3) 1936-0592 2018/04/01 [Refereed][Not invited]
     
    Roads are a pervasive form of disturbance with potential to negatively affect ecohydrological processes. Some of the most rapid growth in road networks is occurring in developing countries, particularly in the tropics, where political agendas are often focused on strengthening the economy, improving infrastructure, bolstering national security, achieving self-sufficiency, and increasing citizen well-being, often at the expense of the environment. We review what is known about road impacts on ecohydrological processes, focusing on aquatic systems, both temperate and tropical. We present seven cases that represent the broader trends of road development and impacts in tropical settings. Many of these process dynamics and impacts are not different from those experienced in temperate settings, although the magnitude of impacts in the tropics may be amplified with intense rainfall and lack of best management practices applied to road construction/maintenance. Impacts of roads in tropical settings may also be unique because of particular organisms or ecosystems affected. We outline a set of best practices to improve road network management and provide recommendations for adopting an agenda of research and road management in tropical settings. Importantly, we call for incorporation of transdisciplinary approaches to further study the effects of roads on ecohydrological processes in the tropics. Specific emphasis should also be placed on collaboration with governments and developers that are championing road development to help identify the drivers of road expansion and thresholds of negative impact, as well as methods of sustainable road construction and maintenance.
  • J. N. Negishi, M. Sakai, K. Okada, A. Iwamoto, T. Gomi, K. Miura, M. Nunokawa, M. Ohhira
    Landscape and Ecological Engineering 14 (1) 55 - 66 1860-188X 2018/01/01 [Refereed][Not invited]
     
    We examined the cesium-137 (137Cs) contamination of river food webs in a gradient of initial fallout deposition (net density estimates 2.5–3.5 months after the Fukushima Daiichi Nuclear Power Plant accident in March 2011), in Fukushima Prefecture, Japan. Litter, aquatic insects, and salmonid fish were collected in five headwater stream reaches (watershed-average fallout density, 368.1–1398.4 kBq/m2) for the measurement of 137Cs concentration and stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) in June 2014. The stable isotope ratios suggested that the detrital food chain was a dominant energy pathway in rivers originating from a basal resource (litter) to primary (aquatic insects) and secondary (fish) consumers. The 137Cs concentration decreased with an increase in the trophic level, with the highest value for litter (10930 ± 5381 Bq/kg, mean ± SD), the lowest for fish (2825 ± 2451 Bq/kg), and the intermediate one for dominant (numerically and biomass-wise) detritivorous insect, Ephemera japonica McLachlan (4605 ± 1970 Bq/kg). 137Cs concentrations of three trophic levels were linearly predicted by the initial fallout amount of 137Cs. The evacuation of the gut contents of E. japonica during field experiments led to a reduction in their 137Cs concentration by approximately 50% within 1–2 day(s) without loss of body weight. This suggested that a substantial portion of 137Cs contamination of E. japonica was derived from highly contaminated fine solids deposited in depositional habitats at a disproportionately high density. Overall, the initial fallout amount of 137Cs was helpful in roughly predicting the contamination levels of headwater river-riparian ecosystems with the detrital food chain as a dominant energy pathway. Long-term monitoring of the dynamics and fates of 137Cs associated with fine organic and inorganic particulates appears important for better prediction of 137Cs contamination of food webs in forested headwater streams.
  • Stream Resource Gradients Drive Consumption Rates of Supplemental Prey in the Adjacent Riparian Zone
    Terui, A, Negishi, J. N, Watanabe, N, Nakamura, F
    Ecosystems 2017/09 [Refereed][Not invited]

MISC

  • Shigeya Nagayama, Morihiro Harada, Yuichi Kayaba, Junjiro N. Negishi  Ecology and Civil Engineering  17-  (1)  29  -40  2014  [Not refereed][Not invited]
     
    直轄区間における河川整備計画や自然再生計画の立案に寄与することを目的に,セグメント 2 に区分される低平な自然堤防帯を流れる沖積低地河川において,イシガイ類を指標生物とした河道内氾濫原環境の簡易な評価手法を開発し,精度検証,評価結果の活用例の提示,課題の抽出を行った.開発した評価手法のフローを以下に示す.まず,(1) イシガイ類の生息可能性を 3 段階評価で表す "回帰モデル評価マップ" と,(2) 氾濫原水域の有無を 2 段階評価で表す "氾濫原水域マップ" を作成する.そして,(3) それらの評価の組み合わせから得られる 6 段階の評価区分を面的に展開した "総合評価マップ" を作成する.高い汎用性を実現するため,評価に要するデータは,直轄区間で一般に取得可能なもののみとした.また,回帰モデルの説明変数として冠水頻度を用い,評価単位として 50 m の正方形メッシュを採用した.精度検証の結果,イシガイ類の生息水域 17 箇所中 15 箇所 (88.2%)は,モデル評価値が高く,氾濫原水域もある最も高い評価区分に該当した.また,非生息水域 20 箇所中 13 箇所 (65.0%)は,氾濫原水域がないと判定される評価区分,もしくは水域はあるが生息可能性がやや劣るとみなされる評価区分に該当していた.以上から,本評価手法は,イシガイ類の面的な生息分布を一定の精度で予測でき,河道内氾濫原環境の現状評価に使用可能であると考えられた.ただし,構築したイシガイ類の生息に関する回帰モデルの適用範囲は,本研究対象地のように,陸域の樹林化が進行した低地河川に限定される.そのため,今後は,異なる特性を持つ河道で適用可能なモデルを構築する必要がある.また,冠水頻度を面的に表現するために行った水位観測所を基準とした水位変動特性の内挿法は,勾配の不連続点や変化点を考慮できていないため,今後は,この点を改善する必要がある.


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