Faculty of Environment and Information Sciences, Division of Natural Environment and Information

Job Title


Research Fields, Keywords

-plant ecology, evolutional ecology, forest ecology, vegetation, growth, reproduction, resource allocation, strategy, distribution, life history, sprout, disturbance, landform, micro-topography, landslide, tree form, habitat segregation, Man and Biosphere, UNESCO, Biosphere Reserve

Mail Address

E-mail address

Graduating School 【 display / non-display


    Chiba University   Faculty of Science   Graduated

Graduate School 【 display / non-display


    Chiba University  Graduate School, Division of Science and Technology  Doctor Course  Completed

Degree 【 display / non-display

  • Doctor of Science -  Chiba University

External Career 【 display / non-display

  • 2002.04

    Tohoku University   Research Assistant  

  • 1997.04

    Research Fellow of the Japan Society for the Promotion of Science (PD)   Research Fellowship for Young Scientists of the Japan Society for the Promotion of Science  

Field of expertise (Grants-in-aid for Scientific Research classification) 【 display / non-display

  • Ecology/Environment


Books 【 display / non-display

  • Transformations of Social-Ecological Systems: Studies in Co-creating Integrated Knowledge Toward Sustainable Futures

    Sato, T., Chabay, I., Helgeson, J. eds. (Part: Contributor , Range: Internatinal Systems Deployed at the Local Level: UNESCO's Man the Biosphere Programme in Japan )

    Springer  2018.12 ISBN: 978-981-13-2326-3

  • Why do we protect the ecosystems?

    Sakai, A. (Part: Single Work )

    Principles and Methods for Ecosystem Risk Management; YNU Leadership Program in Sustainable Living with Environmental Risk eds  2011

     View Summary


Papers 【 display / non-display

  • Changing leaf traits with topographic position in Fagus crenate

    Akihito GOTO, Hirofumi KONDO, Akiko SAKAI

    Nature of Tadami; Bulletin of the Tadami Beech Center ( Tadami Beech Center )  7   2 - 9   2019.04  [Refereed]

    Joint Work

     View Summary

    While leaf traits are known to adaptively differentiate depending on topographic position, such as ridge or valley, intraspecific patterns may be different from interspecific tendencies that have been well studied. In temperate snowy areas of Japan, Fagus crenata is dominant in a wide range of habitats ranging from ridges to valleys, and serves as a fitting material for examining topographical intraspecific leaf changes. We sampled six leaves from the lowest parts of tree crowns from 111 F. crenata of various sizes in Tadami town. Soil water content near stem bases and canopy openness at the leaf sampling points were measured as environmental indices. Topographical leaf changes of F. crenata were detected statistically, when a tree position on the ridge-valley gradient was evaluated by 30 m Laplacian. The results showed that the closer to the ridge, the smaller the leaf area and leaf dry weight, the higher the specific leaf area (SLA), and the smaller the SPAD value (an indicator of chlorophyll content based on area). There was a strong negative correlation between SLA and SPAD value. The detected trends in leaf sizes and SPAD value agreed with common tendencies known as interspecies pattern, but not for SLA tendency. Soil water content and light condition were independent from topographic position, and factors affecting topographic trends in the leaf traits were unclear.

  • Spring leaf phenology of Fagus crenata in snowy region - differences relating to relative height of foliage between and within individuals

    Shiho Nishizaka, Akiko Sakai

    11th International Beech Symposium IUFRO, 18th – 21st September 2018, Viterbo, Italy     23 - 23   2018.09  [Refereed]

    Joint Work

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    The timing of spring leaf emergence is important for the tree carbon gaining strategy in temperate deciduous forests. Leaf phenology of co-occurring trees is known to vary even within a same species, including size-dependent changes (Augspurger & Bartlett, 2003). However, few studies mention variations within individual trees, although physiological and morphological adaptive changes of leaves in the crowns are noticed. In this study, we examined the spring leaf phenology of Fagus crenata, focusing on relative heights of shoots in individual crowns and relative tree heights in a forest. Data was collected in Tadami Town of Fukushima, a typical snowy F. crenata forested area in northern Japan. Leaf flashing dates were detected in an old-growth beech forest (Site 1) and a secondary beech forest (Site 2) in 2017, for the upper and lower shoots of 154 trees of various heights. Forest structures and shoot light conditions were also evaluated. In Site 1, flashing occurred later with increasing tree height, but independently of the relative heights in crowns. In Site 2, flashing occurred earlier on higher trees and on higher shoots in the crowns. This tree height effect in Site 2 was noticeable for trees < 5.5 m. The two patterns were related to local light conditions, resulting from the community structure and snowmelt timing. In Site 1, phenology is accelerated in short trees for effective light acquisition under canopy although it did not explain the lack of the pattern in crowns. While, strong vertical gradient of irradiance in Site 2 may cause short trees and lower shoots to have more shade-leaves and to avoid direct light. Delayed snowmelt also contributes to the late flashing of the lower foliage in Site 2. We suggest that both strategic and passive modifications promote the complex pattern of phenology in F. crenata.

  • Tadami Biosphere Reserve: initiative of a mountainous town for sustainable development to overcome depopulation and aging society, using nature resources

    Wajiro Suzuki, Yosuke Nakano, Akiko Sakai

    Japanese Journal of Ecology ( The Ecological Society of Japan )  66 ( 1 )   135 - 146   2016.06  [Refereed]  [Invited]

    Joint Work

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    We analyzed cases in the Tadami Biosphere Reserve, and specifically explained the background, process, and issues that led to the regional acceptance of the principles of the UNESCO MAB program and the use of this system for regional development.


  • Estimation and enhancement method for publicity of Biosphere Reserves in Japan; suggestion from a comparison with related institutions using internet search engine

    SAKAI Akiko

    Japanese Journal of Ecology ( The Ecological Society of Japan )  66 ( 1 )   165 - 172   2016.06  [Refereed]  [Invited]

    Single Work

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    I made comparisons with other related systems operating in Japan by statistical analysis using numerical data, and made recommendations for future system management.


  • Topographical patterns in the phylogenetic structure of temperate forests on steep mountainous terrain

    Ryo Kitagawa, Makiko Mimura, Akira S. Mori, Akiko Sakai

    AoB PLANTS   7   2015.11  [Refereed]

    Joint Work

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    In rugged terrain subject to active geomorphological processes, the species composition of forest communities changes along topographic gradients over short distances. However, the phylogenetic structure of forests on rugged terrain has rarely been examined. Understanding such structures provides insight into community assembly rules dependent on local environmental conditions. To this end, we tested the topographic trends of measurements of phylogenetic community structure [net relatedness index (NRI) and nearest taxon index] in a catchment covered by temperate forests with complex relief in Japan. We found that phylogenetic structure changed from over-dispersion to clustering with increasing slope inclination, change of slope aspect from south to north and decreasing soil depth. This result suggested that environmental filtering tended to restrict community composition at relatively stressful sites, whereas species interaction functioned more strongly at relatively stress-free sites. Relatively stressful sites were characterized by early-successional species that tended to assemble in certain phylogenetic clades, whereas highly competitive late-successional species associated with lower NRI at relatively stress-free sites. However, despite this significant topographic tendency, phylogenetic community structures were not statistically different from random assumptions in most plots. This obscuration of the phylogenetic structures at the plot level could be interpreted as species adapting to disturbances because they were abundant in this catchment. Accordingly, we suggest that a stochastic process was also important for this community at the plot level, although biotic and abiotic environmental filtering controlled the vegetation structure in the catchment, where disturbances occur frequently because of geomorphological mountain denudation processes owing to active crustal movements and abundant rainfall.


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Review Papers 【 display / non-display

  • Biosphere Reserve as an effective institution for realizing sustainable society

    Akiko Sakai, Hiroyuki Matsuda

    Japanese Journal of Ecology ( The Ecological Society of Japan )  66 ( 1 ) 119 - 120   2016.06  [Refereed]  [Invited]

    Introduction and explanation (scientific journal)   Joint Work

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    As the persons in charge of planning for the special feature, he explained the MAB system and its background, introduced the purpose of the special feature, and the thesis to be composed.


  • Ecological significance of sprouting for tree species-tree sprouting as an attribute of life-history stategy-.

      21   1 - 12   1997

    Introduction and explanation (scientific journal)   Single Work

  • Effects of ground-surface disturbances due to dissection of river valleys on forest vegetation.

    Japanese Journal of Ecology   45   317 - 322   1995

    Introduction and explanation (scientific journal)   Single Work

  • Effects of ground-surface disturbances on pattern of mountain vegetation and tree strategies with special reference to a disturbance tolerant, Euptelea polyandra.

    Doctoral thesis, Chiba University, Chiba     1995

    Introduction and explanation (others)   Single Work

Past of Collaboration and Commissioned Research 【 display / non-display

  • Sprouting strategies of tree plants

    Project Year:  -   

  • Altitudinal Changes of growth and reproduction in woody plants

    Project Year:  -   

  • Theoretical analyses of Sex allocation of plants

    Project Year:  -