SAKAI Akiko

Affiliation

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

Job Title

Professor

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

Related SDGs




The Best Research Achievement in the last 5 years 【 display / non-display

  • 【Published Thesis】 Phylogenetic singnal in the topographic niche of trees: Current and historical significance of habitat structure on the species arrangement pattern within East Asian rugged forests  2020

    【Published Thesis】 Intra-population variation in floral traits of Adonis ramosa (Ranunculaceae)  2020

    【Book】 Transformations of Social-Ecological Systems: Studies in Co-creating Integrated Knowledge Toward Sustainable Futures  2018.12

    【Book】 地域環境学 トランスディシプリナリー・サイエンスへの挑戦  2018.01

Graduating School 【 display / non-display

  •  
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    1987

    Chiba University   Faculty of Science   Graduated

Graduate School 【 display / non-display

  •  
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    1995

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

Degree 【 display / non-display

  • Doctor of Science -  Chiba University

Campus Career 【 display / non-display

  • 2017.03
    -
    Now

    Duty   Yokohama National UniversityFaculty of Environment and Information Sciences   Division of Natural Environment and Information   Professor  

  • 2009.09
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    2017.02

    Duty   Yokohama National UniversityFaculty of Environment and Information Sciences   Division of Natural Environment and Information   Associate Professor  

  • 2007.10
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    2009.08

    Duty   Yokohama National UniversityResearch Institute of Environment and Information Sciences   Division of Natural Environment and Information   Assistant Professor  

  • 2021.04
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    Now

    Concurrently   Yokohama National UniversityInterfaculty Graduate School of Innovative and Practical Studies   Professor  

  • 2018.04
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    Now

    Concurrently   Yokohama National UniversityGraduate School of Environment and Information Sciences   Department of Natural Environment   Professor  

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External Career 【 display / non-display

  • 2002.04
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    2003.03

    Tohoku University   Research Assistant  

  • 1997.04
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    2000.03

    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

    教科書

Papers 【 display / non-display

  • Intra-population variation in floral traits of Adonis ramosa (Ranunculaceae)

    Nanami KONDO, Hirofumi KONDO, and Akiko SAKAI

    Nature of Tadami, Bulletin of the Tadami Beech Center   8 (in press)   2020  [Refereed]

    Joint Work

     View Summary

    Variation in flower traits within a population and its factors were investigated using Adonis ramosa, focusing on (1) differences in the amount of resources possessed by individuals and (2) differences in flowering days. The survey was conducted in a population located in Tadami Town. Plant size, number of petals, number of stamens, number of ovules,three kinds of flower area size, male fitness (number of stamens x freqency of insect visit), and female fitness (number of mature seeds) were recorded for 84 flowers of 71 individuals. (1) The bigger individuals had larger flowers with more stamens and ovules. Of the flower area sizes, the display size was related to the male fitness and the size of petals overlap area was related to the male and female fitness. (2) As a result of comparison of individuals in which only one flower was produced in either the first or second half of the flowering period of the population, excluding the effect of individual size, the first flowering group had many stamens and ovules, but the number of insect visits and the fertility rate were higher in the late flowering group. Since A. ramosa has only a few flowers, the flower traits are adjusted at the individual flower level to increase fitness. In addition, the flowering day and the amount of resources that can be allocated to reproduction differ among individuals due to differences in the environment and other factors. These factors may contribute the intra-population variation in flower traits, which observed in the A. ramosa population.

  • Phylogenetic singnal in the topographic niche of trees: Current and historical significance of habitat structure on the species arrangement pattern within East Asian rugged forests

    KITAGAWA Ryo, MIMURA Makiko, MORI Akira S., and SAKAI Akiko

    Ecological Research   (in press)   2020  [Refereed]

    Joint Work

     View Summary

    Topography often promotes habitat heterogeneity and is a major factor in fine-grained changes in vegetation. Especially in temperate mountainous regions of East Asia, the distribution of tree species is largely explained by topographic niche differentiation. Because species niche is at least partially a historical product through the evolution of functional traits, phylogenetic signals are expected in the topographic arrangement pattern of species, although this has not been fully investigated. Thus, we examined common temperate trees in a 306 ha watershed on Mt Tanzawa, central Japan. The topographic niche position of each species was explained with two principle component analysis (PCA) axes, which aligned with the topographic structure of the watershed. High scores on PC1 reflected lower elevations, steeper slopes, and nearby valleys. Higher scores on PC2 indicated thicker soil, more south-facing slopes, slighter slope inclinations, and nearby valleys. The former indicated the species were aligned on a habitat gradient of land-surface instability, for which the gradient is typical under the current geological conditions. The latter indicated that a niche axis for resource availability relating to water, nutrients, and light or heat existed. A phylogenetic signal, identified by Pagel’s λ and the Mantel test, was detected for PC2 scores. However, the species arrangement along PC1 was independent of phylogeny. Our results suggested that the topographic niche of tree species in this area is caused by both relatively recently derived traits regarding adaptation to unstable land surfaces and conservative traits derived through plant evolution.

  • 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

     View Summary

    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.

    DOI

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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.

    DOI

  • 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

Grant-in-Aid for Scientific Research 【 display / non-display

  • Grant-in-Aid for Scientific Research(C)

    Project Year: 2014.04  -  2017.03 

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:  -   

 

Council/Academic activity outside the university 【 display / non-display

  • Japanese Coordinate Committee for MAB

    2007.10
     
     

    Others