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393 results on '"Otsuki, Kyoichi"'

112. A model relating transpiration for Japanese cedar and cypress plantations with stand structure

Author

Komatsu, Hikaru, primary, Shinohara, Yoshinori, additional, Kumagai, Tomo’omi, additional, Kume, Tomonori, additional, Tsuruta, Kenji, additional, Xiang, Yang, additional, Ichihashi, Ryuji, additional, Tateishi, Makiko, additional, Shimizu, Takanori, additional, Miyazawa, Yoshiyuki, additional, Nogata, Mari, additional, Laplace, Sophie, additional, Han, Tseng, additional, Chiu, Chen-Wei, additional, Ogura, Akira, additional, Saito, Takami, additional, and Otsuki, Kyoichi, additional

Published
2014
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113. Spatio-temporal streamflow generation in a small, steep headwater catchment in western Japan.

Author

Sun, Haotian, Kasahara, Tamao, Otsuki, Kyoichi, Saito, Takami, and Onda, Yuichi

Subjects
STREAM measurements, WATERSHEDS, SPATIO-temporal variation, SOIL moisture, GROUNDWATER
Abstract

Headwaters contribute a substantial part of the flow in river networks. However, spatial variations of streamflow generation processes in steep headwaters have not been well studied. In this study, we examined the spatio-temporal variation of streamflow generation processes in a steep 2.98-ha headwater catchment. The time when baseflow of the upstream section exceeded that downstream was coincident with the time when the riparian groundwater switched from downwelling to upwelling. This suggests that upwelling of the riparian groundwater increased considerably in the upstream section during the wet period, producing a shift in the relative size of baseflow between the upstream and downstream sections. The timing of fluctuations among hillslope soil moisture, hillslope groundwater and streamflow reveals that the hillslope contributed to storm flow, but this contribution was limited to the wet period. Overall, these results suggest that streamflow generation has strong spatial variations, even in small, steep headwater catchments. EDITOR A. Castellarin ASSOCIATE EDITOR X. Chen [ABSTRACT FROM AUTHOR]

Published
2017
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114. Differences in sap flux-based stand transpiration between upper and lower slope positions in a Japanese cypress plantation watershed.

Author

Kume, Tomonori, Tsuruta, Kenji, Komatsu, Hikaru, Shinohara, Yoshinori, Katayama, Ayumi, Ide, Jun'ichiro, and Otsuki, Kyoichi

Subjects
PLANT transpiration, CYPRESS, CHAMAECYPARIS obtusa, WATERSHEDS, EVAPOTRANSPIRATION
Abstract

This study investigated the difference in stand transpiration ( E) between upper (UP) and lower (LP) slope plots of a Japanese cypress ( Chamaecyparis obtusa) watershed to obtain catchment-scale E estimates. Sap flux-based stand-scale E estimates were conducted on the UP and LP, which had contrasting stand structures (diameter at breast height and tree height) despite being the same age. The plant area index was similar in the UP and LP, while the total sapwood area ( AS_stand) and the mean sap flux density ( JS) in the UP were 23% and ~30% lower, respectively, than those of the LP. Stand-scale E is the product of the AS_stand and JS in a stand. As a result, E in the UP was ~50% lower than that in the LP. This ratio was relatively constant throughout the year, which was supported by a similar decline in E, which resulted from soil water decline in the UP and LP. Canopy conductance ( GC) in the UP was ~50% smaller than that of the LP. In contrast to previous studies that showed a consistent JS along a slope, the differences in E between the UP and LP were caused by differences in AS_stand and JS, probably because the UP exhibited a lower GC per unit leaf area than the LP. Additionally, evapotranspiration ( ET), the sum of sap flux-scaled E plus rainfall interception, was 8-14% lower than the catchment water balance ET (precipitation minus runoff), which suggests the feasibility of calculating sap flux-scaled E for the two slope positions. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Published
2016
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117. Moso-bamboo Forests in Japan

Author

Shinohara, Yoshinori, primary, Kume, Tomonori, additional, Ichihashi, Ryuji, additional, Komatsu, Hikaru, additional, and Otsuki, Kyoichi, additional

Published
2014
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123. Radial variations in xylem sap flow and their effect on wholetree water use estimates.

Author

Zhang, Jian‐Guo, He, Qiu‐Yue, Shi, Wei‐Yu, Otsuki, Kyoichi, Yamanaka, Norikazu, and Du, Sheng

Subjects
ACTINIC flux, SAPWOOD, PLANT transpiration, FORESTRY research, THUJA
Abstract

To estimate whole-tree or stand transpiration based on sap flow measurements, sap flux density (Fd) needs to be scaled up over the entire sapwood area. We investigated radial variations in Fd in the dominant oak (Quercus liaotungensis) and a commonly occurring oriental arborvitae (Platycladus orientalis) species using Granier-type thermal dissipation probes in a semi-arid forest in northern China. Our results show that Fd in oak trees reached a maximum just below the cambium and decreased towards the inner sapwood. On the other hand, radial sap flow patterns in oriental arborvitae trees differed among individuals. Fd values at different depths within an individual were highly correlated with each other in both species. We assessed the error of single-depth measurements when upscaling to whole-tree water use using multi-depth measurements as a reference. Omitting radial variations resulted in an overestimation of daily water use by 38% and 78% in oak trees with sapwood depths of approximately 2 and 3 cm, respectively. The outer sapwood annuli (0-1 cm) contributed 74% and 65% to the total water use in the two classes of sapwood depth. These contribution coefficients may be used as correction indices for estimating whole-tree water use. Errors of omitting radial variations in oriental arborvitae trees ranged from 42% to 21%. Using relatively long sensors (e.g. 2 cm) may improve the estimate accuracy in this species. The results would be applicable to the estimation of tree or stand transpiration based on routine depth measurements using one set of sensors. It is suggested that radial variations should be considered for accurately upscaling locally measured sap flow data to whole-tree water use in trees with wide sapwood and that different approaches may be applied to species with different patterns of radial variations. [ABSTRACT FROM AUTHOR]

Published
2015
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