Kyushu University Academic Staff Educational and Research Activities Database
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Kotaro SAKUTA Last modified date:2023.12.13

Assistant Professor / Forest Environmental Sciences
Department of Agro-environmental Sciences
Faculty of Agriculture

Graduate School
Undergraduate School

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Academic Degree
Synchronistical features of leaf physiological functions with hydraulic resistance in tree water use.
Country of degree conferring institution (Overseas)
Field of Specialization
Silviculture, Forest Ecology, Tree physiological ecology, Tree medical science
Total Priod of education and research career in the foreign country
Research Interests
  • Distribution and situation of the beech (Fagus crenata) stands in Kyushu island
    keyword : Fagus crenata, plant community, flowering, fruition, distribution
  • Studies for coniferous plantations productivity
    keyword : Cryptomeria japonica, Chamaecyparis obtusa, coniferous plantation, mountainous area, site environment
  • Forest dynamics after natural and artificial disturbances
    keyword : Forest harvest, Stands damages by typhoon, Diversity of plant species, Stand productivity, Forest succession
  • Trees physiological ecological characteristics within the forests in warm-temperate zone
    keyword : Distribution of substances in trees, Physiological characteristics of trees, Forests in warm-temperate zone, Recruitment of vegetations
  • Physiological ecological studies for water relation of trees
    keyword : Forest management, planting shock, water potential, site factor, hydraulic resistance
Academic Activities
1. Yosuke Funato, Koji Itabashi, Seiichi Kanetani, Kotaro Sakuta4, Characteristics of beech mixed forest distributed at low elevations on Mt. Toishi, northern Kyushu, in the upper warm-temperate zone of Japan, Ecological Research, 10.1111/1440-1703.12423, 38, 6, 753-763, 2023.09, The aim of this study was to clarify the structure and regeneration status of mixed beech (Fagus crenata) forest on Mt. Toishi in the Sangun mountain range in northern Kyushu, a relatively low-latitude region in Japan, with emphasis on forests at lower elevations. We focused on a mixed beech forest at a low elevation of Mt. Toishi and compared the forest structure of the target stands, including tree species and size, with the forest structure near the peaks of Mt. Toishi and Mt. Sangun. Deciduous broad-leaf trees were dominant near
the peaks, while evergreen broad-leaf trees dominated at lower elevations, whereas the relative dominance of beech trees was not significantly different. Near the peaks, the number of large-diameter beech trees forming the canopy decreased, and small-diameter trees were present. The proportion of smallsized trees was lower in the low-elevation forest area than in the forest area near the peak. Even at lower elevations, juvenile beech trees grew in limited areas on steep slopes along forest roads. These sites suggested that regeneration of beech populations is possible even at low elevation..
2. Kazuki Ito, Tetsuji Ota, Nobuya Mizoue, Shigejiro Yoshida, Kotaro SAKUTA, Akio Inoue, Satoshi Ito, Hiroyuki Okada, Differences in growth responses between Cryptomeria japonica and Chamaecyparis obtusa planted in group selection openings in Kyushu, southern Japan, Journal of Forest Research, Volume 22, Number 2, 126-130, 2017.02, We quantified the differences in growth responses between Cryptomeria japonica and Chamaecyparis obtusa trees in approximately 0.1-ha group selection openings in southern Japan. We measured the position, height (H), and diameter at ground level (D) of 6- and 13-year-old C. japonica and C. obtusa trees that were planted in two respective openings. The annual H and D growth of C. japonica increased until trees were 10 and 8 m, respectively, distant from the nearest edge of the opening. For C. obtusa, the annual H and D growth increased slightly until the trees were 6 m distant from the nearest edge, but they did not significantly differ between 6 and 18 m distant from the nearest edge. While the shortest distance from the edge explained 63% and 50% of the variation in annual H and D growth, respectively, of C. japonica, it explained only 20% and 18% of the annual H and D growth, respectively, of C. obtusa. Our result demonstrates that C. obtusa is less sensitive to edge effects than C. japonica. We conclude that C. obtusa is likely to be more suitable than C. japonica for planting within 0.1-ha group openings, as it will result in faster early stage growth, with less variation, within the openings..
3. Ryoko Hirata, Satoshi Ito, Keisuke Eto, Kotaro SAKUTA, Nobuya Mizoue, Yasushi Mitsuda, Early growth of hinoki (Chamaecyparis obtusa) trees under different topography and edge aspects at a strip-clearcut site in Kyushu, Southern Japan, Journal of Forest Research, Volume 20, Number 6, 522-529, 2015.10, The positive and negative effects of the residual stand edge at a strip-clearcut site were examined on the initial growth of hinoki (Chamaecyparis obtusa) planted in areas with diverse topography. On the south edge, the gap light index was lower than on the north edge and strip center; however, the vapor pressure deficit was also lower than on the north edge and strip center, which resulted in
lower physiological stress of hinoki on the south edge. Tree size on the south edge did not exceed that on the north edge and strip center. These results indicated that low light conditions due to residual trees negatively affected growth on the south edge even under the positive effect of microclimate alleviation. In valley, tree size in the second year after planting was smaller than on ridge and slope; however, tree growth during the following 2 years was higher in valley. Surface soil in valley was thinner with rockier substrates than on ridge and slope; that is, soil sedimentation type and substrates influenced the initial growth of hinoki with undeveloped roots, and after that,
topography started to influence growth, probably because hinoki roots penetrated into deeper soil, which is influenced by the water gathering capacity of the valley. The initial growth of hinoki at the strip-clearcut site was predominantly affected by light rather than microclimate alleviation. This alleviation is expected to disappear when hinoki trees planted in the strip center grow enough to give
additional shade to slow-growing edge hinoki..
4. Akio Inoue, Shingo Sakamoto, Haruka Kitazono, Kotaro SAKUTA, Development of Two-way Volume Equation for Bamboo, Phyllostachys nigra, J. For. Plann. , 18, 13-19, 2012.11.
5. Akio, Inoue, Haruka, Tateishi, Kotaro SAKUTA, Kazukiyo Yamamoto, Nobuya Mizoue, Fumiaki Kitahara, Relationships of light environment to stand attributes in a stand of bamboo, Phyllostachys pubescens, Ecological Engineering, 10.1016/j.ecoleng.2011.09.007, 38, 1, 135-139, 2012.01.
6. Suyama,K.and Sakuta,K.(2009) Relationships between specific leaf area, leaf SPAD value and light environment in the crown of Prunus pendula Maxim., Bull. Kyushu Univ. For., 90, 39-49.
7. K. Sakuta, S. Taniguchi, A. Inoue, N. Mizoue (2009) Effects of strip-cutting on stand floor micro climate and tree-species diversity in a Japanese cypress plantation., J. Jpn. For. Soc., 91(2), 86-93.
8. Takafumi Inoue, Tsutomu Enoki, Naoaki Tashiro, Kotaro Sakuta, Susumu Inoue, Effects of topography and planted trees on the distribution of naturally regenerated broad-leaved trees in a 140-year-old Cryptomeria japonica plantation in northern Kyushu, Japan, Journal of Forest Research, Volume 13, Number 6, 365-371, 2008.12.
9. Kohama T., Mizoue N., Ito S., Inoue A., Sakuta K. and Okada H., Effects of light microsite conditions on tree size of 6-year-old Cryptomeria japonica planted in a group selection opening, Journal of Forest Research, 11: 235-242, 2006.09.
10. Ito, S., Sakuta, K. and Gyokusen, K., Distribution of hydraulic resistance in seedlings, sprouts and an adult tree of Pasania edulis Makino, Ecol. Res., 10.1007/BF02347936, 10, 2, 143-149, 10, 143-149, 1995.01.
11. Ito, S., Sakuta, K. and Gyokusen, K., Distribution of hydraulic resistance within shoots of Pasania edulis Makino grown in sunny and shaded crown, Bull. Kyushu Univ. Forests, 72, 11-19, 1995.01.
Membership in Academic Society
  • Japanese Society of Forest Genetics and Tree Breeding
  • Tree Health Research Society, Japan
  • The Kyushu Forest Society
  • The Japanese Society of Forest Environment
  • The Japanese Forest Society
  • The Ecological Society of Japan
  • Japanese Society of Revegetation Technology