Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Kyoichi Otsuki Last modified date:2021.06.16

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

1. Farahnak, M., Mitsuyasu, K., Hishi, T., Katayama, A., Chiwa, M., Jeong, S., Otsuki, K., Sadeghi, S. M. M. & Kume, A., Relationship between very fine root distribution and soil water content in pre-and post-harvest areas of two coniferous tree species, Forests, 10.3390/f11111227, 11, 11, 1227, 2020.11.
2. Jeong Seonghun, Kyoichi Otsuki, Yoshinori Shinohara, Akio Inoue, Ryuji Ichihashi, Stemflow estimation models for Japanese cedar and cypress plantations using common forest inventory data, Agricultural and Forest Meteorology, 10.1016/j.agrformet.2020.107997, 290, 2020.08,  本論文は、森林の樹幹流量は従来過小評価されていたが、過密人工林では樹幹流量は無視できないほど大きいこと、樹幹流量は一般的な林分構造指標である立木密度と胸高直径を変数として推定可能であることを報告した論文である。.
3. Qiu Yue He, Mei Jie Yan, Yoshiyuki Miyazawa, Qiu Wen Chen, Ran Ran Cheng, Kyoichi Otsuki, Norikazu Yamanaka, Sheng Du, Sap flow changes and climatic responses over multiple-year treatment of rainfall exclusion in a sub-humid black locust plantation, Forest Ecology and Management, 10.1016/j.foreco.2019.117730, 457, 2020.02.
4. Ryuji Ichihashi, Hikaru Komatsu, Tomonori Kume, Yoshinori Shinohara, Kenji Tsuruta, Kyoichi Otsuki, Effects of thinning on canopy transpiration of a dense Moso bamboo stand in Western Japan, Journal of Forest Research, 10.1080/13416979.2019.1647592, 24, 5, 285-291, 2019.09, [URL].
5. Moein Farahnak, Keiji Mitsuyasu, Kyoichi Otsuki, Kuniyoshi Shimizu, Atsushi Kume, Factors determining soil water repellency in two coniferous plantations on a hillslope, Forests, 10.3390/f10090730, 10, 9, 2019.09.
6. Kenji Tsuruta, Hikaru Komatsu, Tomonori Kume, Kyoichi Otsuki, Yoshiko Kosugi, Ken'ichiro Kosugi, Relationship between stem diameter and transpiration for Japanese cypress trees
Implications for estimating canopy transpiration, Ecohydrology, 10.1002/eco.2097, 12, 5, 2019.07.
7. Jeong Seonghun, Otsuki Kyoichi, Farahnak Moein, Relationship between stand structures and rainfall partitioning in dense unmanaged Japanese cypress plantations, Journal of Agricultural Meteorology, 10.2480/agrmet.D-18-00030, 75, 2, 92-102, 2019.04.
8. Seonghun Jeong, Kyoichi Otsuki, Akio Inoue, Yoshinori Shinohara, Marked difference of rainfall partitioning in an unmanaged coniferous plantation with high stand density, Journal of Forest Research, 10.1080/13416979.2018.1551116, 24, 2, 107-114, 2019.03.
9. Moein Farahnak, Keiji Mitsuyasu, Seonghun Jeong, Kyoichi Otsuki, Masaaki Chiwa, Seyed Mohammad Moein Sadeghi, Atsushi Kume, Soil hydraulic conductivity differences between upslope and downslope of two coniferous trees on a hillslope, Journal of Forest Research, 10.1080/13416979.2019.1590967, 24, 3, 143-152, 2019.01.
10. Masaaki Chiwa, Hirokazu Haga, Tamao Kasahara, Makiko Tateishi, Takami Saito, Hiroaki Kato, Kyoichi Otsuki, Yuichi Onda, Effect of forest thinning on hydrologic nitrate exports from a N-saturated plantation, Journal of Forestry Research, 10.1007/s11676-018-0784-5, 31, 2, 387-395, 2018.09.
11. Ayumi Katayama, Tsutomu Enoki, Tomonori Kume, Kyoichi Otsuki, Characteristics of soil respiration in upper and lower slope positions with different aboveground biomass: a case study in a Japanese cypress forest, Journal of Agricultural Meteorology, 10.2480/agrmet.D-17-00019, 74, 2, 63-70, 2018.04, [URL].
12. Kenji Tsuruta, Tomonori Kume, Hikaru Komatsu, Kyoichi Otsuki, Effects of soil water decline on diurnal and seasonal variations in sap flux density for differently aged Japanese cypress (Chamaecyparis obtusa) trees, Annals of Forest Research, 10.15287/afr.2017.938, 61, 1, 5-18, 2018.01.
13. Xinchao Sun, Yuichi Onda, Kyoichi Otsuki, Hiroaki Kato, Takashi Gomi, Xueyan Liu, Change in evapotranspiration partitioning after thinning in a Japanese cypress plantation, Trees-Structure and Function, 10.1007/s00468-017-1555-1, 31, 5, 1411-1421, 2017.10, [URL].
14. Ryuji Ichihashi, Chen‐Wei Chiu, Hikaru Komatsu, Tomonori Kume, Yoshinori Shinohara, Makiko Tateishi, Kenji Tsuruta, Kyoichi Otsuki, Contribution of lianas to community-level canopy transpiration in a warm-temperate forest, Functional Ecology, 10.1111/1365-2435.12881, 31, 9, 1690-1699, 2017.09, [URL].
15. Ken’ichi Shinozuka, Masaaki Chiwa, Ichiro Tayasu, Chikage Yoshimizu, Kyoichi Otsuki, Atsushi Kume, Differences in Stream Water Nitrate Concentrations between a Nitrogen-Saturated Upland Forest and a Downstream Mixed Land Use River Basin, Hydrology, 10.3390/hydrology4030043, 4, 3, 43, 2017.09, [URL].
16. Xianwei Zhao, Zhiyuan Fu, Haotian Sun, Kyoichi Otsuki, Jingshan Yu, Guoqiang Wang, Temporal and spatial variations of vegetation response to dynamic change of meteorological factors and groundwater in the Heihe River Basin, China, Journal of the Faculty of Agriculture, Kyushu University, 62, 2, 503-511, 2017.09.
17. Yoshiyuki Miyazawa, Akio Inoue, Atsushi Maruyama, Kyoichi Otsuki, Thomas W. Giambelluca, Transpiration of trees in a cool temperate forest on Mt. Aso, Japan: comparison of model simulation and measurements, Ecological Research, 10.1007/s11284-017-1471-2, 32, 4, 547-557, 2017.07, [URL].
18. Haotian Sun, Tamao Kasahara, Kyoichi Otsuki, Makiko Tateishi, Takami Saito, Yuichi Onda, Effects of Thinning on Flow Peaks in a Forested Headwater Catchment in Western Japan, Water, 10.3390/w9060446, 9, 6, 2017.06, [URL].
19. Takami Saito, Tomo'omi Kumagai, Makiko Tateishi, Nakako Kobayashi, Kyoichi Otsuki, Thomas W. Giambelluca, Differences in seasonality and temperature dependency of stand transpiration and canopy conductance between Japanese cypress (Hinoki) and Japanese cedar (Sugi) in a plantation, Hydrological Processes, 10.1002/hyp.11162, 31, 10, 1952-1965, 2017.05, [URL].
20. Haotian Sun, Tamao Kasahara, Kyoichi Otsuki , Takami Saito, Yuichi Onda, Spatio-temporal streamflow generation in a small, steep headwater catchment in western Japan, Hydrological Sciences Journal, 10.1080/02626667.2016.1266635, 62, 5, 818-829, 2017.04.
21. Miho Nagano, Akio Inoue, Kenshi Sankoda, Yoshiyuki Miyazawa, Atsushi Maruyama, Masahiro Takagi, Kyoichi Otsuki, Observation of canopy interception ratio in old-aged low-density Japanese cypress plantations in the Aso District, Southern Japan, Nihon Ringakkai Shi/Journal of the Japanese Forestry Society, 10.4005/jjfs.99.70, 99, 2, 70-73, 2017.01.
22. Mei Jie Yan, Jian Guo Zhang, Qiu Yue He, Wei Yu Shi, Kyoichi Otsuki, Norikazu Yamanaka, Sheng Du, Sapflow-based stand transpiration in a semiarid natural oak forest on China's loess plateau, Forests, 10.3390/f7100227, 7, 10, 2016.10.
23. Yoshinori Shinohara, Sohei Otani, Tetsuya Kubota, Kyoichi Otsuki, Kazuki Nanko, Effects of plant roots on the soil erosion rate under simulated rainfall with high kinetic energy, Hydrological Sciences Journal, 10.1080/02626667.2015.1112904, 61, 13, 2435-2442, 2016.10.
24. Tomonori Kume, Kenji Tsuruta, Hikaru Komatsu, Yoshinori Shinohara, Ayumi Katayama, Jun'ichiro Ide, Kyoichi Otsuki, Differences in sap flux-based stand transpiration between upper and lower slope positions in a Japanese cypress plantation watershed, Ecohydrology, 10.1002/eco.1709, 9, 6, 1105-1116, 2016.09, 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..
25. Chen-Wei Chiu, Hikaru Komatsu, Katayama Ayumi, Kyoichi Otsuki, Scaling-up from tree to stand transpiration for a warm-temperate multi-specific broadleaved forest with a wide variation in stem diameter, Journal of Forest Research, 10.1007/s10310-016-0532-7, 21, 4, 161-169, 2016.08.
26. Chen Wei Chiu, Tomonori Kume, Hikaru Komatsu, Han Tseng, Tsong Huei Wey, Kyoichi Otsuki, Seasonal changes of azimuthal, radial, and tree-to-tree variations in sap flux affect stand transpiration estimates in a Cryptomeria japonica forest, central Taiwan, Journal of Forest Research, 10.1007/s10310-016-0525-6, 21, 4, 151-160, 2016.08.
27. Hikaru Komatsu, Yoshinori Shinohara, Tomonori Kume, Kenji Tsuruta, Kyoichi Otsuki, Does measuring azimuthal variations in sap flux lead to more reliable stand transpiration estimates?, Hydrological Processes, 10.1002/hyp.10780, 30, 13, 2129-2137, 2016.06, Stand transpiration (E) estimated using the sap-flux method includes uncertainty induced by variations in sap flux (F) within a tree (i.e. radial and azimuthal variations) and those between trees. Unlike radial variations, azimuthal variations are not particularly systematic (i.e. higher/lower F is not.
28. Katayama Ayumi, Tomonori Kume, Mizue Ohashi, Kazuho Matsumoto, Michiko Nakagawa, Takami Saito, Tomo'omi Kumagai, Kyoichi Otsuki , Characteristics of wood CO2 efflux in a Bornean tropical rainforest, Agricultural and Forest Meteorology, 10.1016/j.agrformet.2016.01.140, 220, 190-199, 2016.04.
29. Xinchao Sun, Yuichi Onda, Kyoichi Otsuki, Hiroaki Kato, Takashi Gomi, The effect of strip thinning on forest floor evaporation in a Japanese cypress plantation, Agricultural and Forest Meteorology, 10.1016/j.agrformet.2015.10.006, 216, 48-57, 2016.01, [URL].
30. Yoshinori Shinohara, Delphis F. Levia,, Hikaru Komatsu, Mari Nogata, Kyoichi Otsuki, Comparative modeling of the effects of intensive thinning on canopy interception loss in a Japanese cedar (Cryptomeria japonica D. Don) forest of western Japan, Agricultural and Forest Meteorology, 10.1016/j.agrformet.2015.08.257, 214, 148-156, 2015.12, [URL].
31. Jian-Guo Zhang, Qiu-Yue He, Wei-Yu Shi,, Kyoichi Otsuki, Norikazu Yamanaka, Sheng Du, Radial variations in xylem sap flow and their effect on whole-tree water use estimates, Hydrological Processes, 10.1002/hyp.10465, 29, 24, 4993-5002, 2015.11, [URL].
32. Saito Takami, Yamamoto Kazuyuki, Komatsu Misako, Matsuda Hiroki, Yunohara Shuji, Komatsu Hikaru, Tateishi Makiko, Xiang Yang, Otsuki K, Kumagai Tomoomi, Using airborne LiDAR to determine total sapwood area for estimating stand transpiration in plantations, Hydrological Processes, 10.1002/hyp.10482, 29, 24, 5071-5087, 2015.11, [URL].
33. Makiko Tateishi, Yang Xiang, Takami Saito, Kyoichi Otsuki, Tamao Kasahara, Changes in canopy transpiration of Japanese cypress and Japanese cedar plantations because of selective thinning, Hydrological Processes, 10.1002/hyp.10700, 29, 24, 5088-5097, 2015.11, [URL].
34. Hikaru Komatsu, Yoshinori Shinohara, Kyoichi Otsuki , Models to predict changes in annual runoff with thinning and clearcutting of Japanese cedar and cypress plantations in Japan, Hydrological Processes, 10.1002/hyp.10520, 29, 24, 5120-5134, 2015.11, [URL].
35. Kenji Tsuruta, Hikaru Komatsu, Tomonori Kume, Yoshinori Shinohara, Kyoichi Otsuki, Canopy transpiration in two Japanese cypress forests with contrasting structures, Journal of Forest Research, 10.1007/s10310-015-0495-0, 20, 5, 464-474, 2015.10, [URL].
36. Yoshinori Shinohara, Shohei Otani, Tetsuya Kubota, Kyoichi Otsuki , Kazuo Nanko, Effects of plant roots on the soil erosion rate under simulated rainfall with high kinetic energy, Hydrological Sciences Journal, DOI:10.1080/02626667.2015.1112904, 2015.10, [URL].
37. Masaaki Chiwa, Takami Saito, Hirokazu Haga, Hiroaki Kato, Kyoichi Otsuki , Yuichi Onda, A Nitrogen-Saturated Plantation of and in Japan Is a Large Nonpoint Nitrogen Source, Journal of Environmental Quality, doi:10.2134/jeq2014.09.0401, 44, 4, 1225-1232, 2015.07, [URL].
38. Yoshinori Shinohara, Komatsu H, Otsuki K, Variations in sapwood and intermediate wood thicknesses for Japanese cedar: their impacts on sapwood area estimates, Hydrological Research Letters, 10.3178/hrl.9.35, 9, 2, 35-40, 2015.06, [URL].
39. Ichihashi, Ryuji, Komatsu, Hikaru, Kume, Tomonori, Onozawa, Yuka, Shinohara Y, Tsuruta, Kenji, Otsuki K, Stand-scale transpiration of two Moso bamboo stands with different culm densities, Ecohydrology, 10.1002/eco.1515, 8, 3, 450-459, 2015.04, [URL].
40. Yoshinori Shinohara, Kyoichi Otsuki, Comparisons of soil-water content between a Moso bamboo (Phyllostachys pubescens) forest and an evergreen broadleaved forest in western Japan, Plant Species Biology, 10.1111/1442-1984.12076, 30, 2, 96-103, 2015.04.
41. Xue, Bao-Lin, Li, Zhanling, Yin, Xin-An, Zhang, Tieliang, Iida, Shin'ichi, Otsuki K, Ohta, Takeshi, Guo, Qinghua, Canopy conductance in a two-storey Siberian boreal larch forest, Russia, Hydrological Processes, 10.1002/hyp.10213, 29, 6, 1017-1026, 2015.03.
42. Qingqing Fang, Lei Zhang, Haotian Sun, Guoqiang Wang, Zongxue Xu, Kyoichi Otsuki, A rainfall simulation study of soil erodibility and available nutrient losses from two contrasting soils in China, Journal of the Faculty of Agriculture, Kyushu University, 60, 1, 235-242, 2015.02.
43. Suk Woo Kim, Kyoichi Otsuki, Yoshinori Shinohara, Kun Woo Chun, Distribution and mobilization of large woody debris in a mountain stream network, Gangwon-Do, South Korea, Journal of the Faculty of Agriculture, Kyushu University, 60, 1, 251-258, 2015.02.
44. Suk Woo Kim, Kun Woo Chun, Kyoichi Otsuki, Yoshinori Shinohara, Man Il Kim, Min Seok Kim, Dong Kyun Lee, Jung Il Seo, Byoung Koo Choi, Heavy rain types for triggering shallow landslides in South Korea, Journal of the Faculty of Agriculture, Kyushu University, 60, 1, 243-249, 2015.02.
45. Masaaki Chiwa, Naoko Higashi, Otsuki K, Hiroki Kodama, Tohru Miyajima, Kazuhiko Takeda, Hiroshi Sakugawa, Sources of hydroxyl radical in headwater streams from nitrogen-saturated forest, Chemosphere, 10.1016/j.chemosphere.2014.02.046, 119, 1386-1390, 2015.01, [URL].
46. Masaaki Chiwa, Takami Saito, Hirokazu Haga, Hiroaki Kato, Kyoichi Otsuki, Yuichi Onda, A nitrogen-saturated plantation of Cryptomeria japonica and Chamaecyparis obtusa in Japan is a large nonpoint nitrogen source, Journal of Environmental Quality, 10.2134/jeq2014.09.0401, 44, 4, 1225-1232, 2015.01.
47. Komatsu, Hikaru, Shinohara Y, Kumagai, Tomo'orni, Tsuruta, Kenji, Xiang, Yang, Ichihashi, Ryuji, Tateishi, Makiko, Shimizu, Takanori, Miyazawa, Yoshiyuki, Nogata, Mari, Laplace, Sophie, Han, Tseng, Chiu, Chen-Wei, Ogura, Akira, Saito, Takami, Otsuki K, A model relating transpiration for Japanese cedar and cypress plantations with stand structure, FOREST ECOLOGY AND MANAGEMENT, 10.1016/j.foreco.2014.08.041, 334, 301-312, 2014.12, [URL].
48. Xinchao Sun, Yuichi Onda, Kyoichi Otsuki, Hiroaki Kato, Akiko Hirata, Takashi Gomi, The effect of strip thinning on tree transpiration in a Japanese cypress (Chamaecyparis obtusa Endl.) plantation, Agricultural and Forest Meteorology, 10.1016/j.agrformet.2014.06.011, 197, 123-135, 2014.10.
49. Sun, Xinchao, Onda, Yuichi, Kato, Hiroaki, Otsuki K, Gomi, Takashi, Partitioning of the total evapotranspiration in a Japanese cypress plantation during the growing season, ECOHYDROLOGY, 10.1002/eco.1428, 7, 3, 1042-1053, 2014.06.
50. Katayama A, Kume, Tomonori, Komatsu, Hikaru, Ohashi, Mizue, Matsumoto, Kazuho, Ichihashi, Ryuji, Kumagai, Tomo'omi, Otsuki K, Vertical variations in wood CO2 efflux for live emergent trees in a Bornean tropical rainforest, Tree Physiology, 10.1093/treephys/tpu041, 34, 5, 503-512, 2014.05, [URL].
51. Observation of canopy interception loss in an oak forest.
52. Jung Il Seo, Yong Rae Kim, Kyoichi Otsuki, Suk Woo Kim, Kyu Jin Yeom, Jae Seon Yi, Young Sang Ahn, Tsugio Ezaki, Kun Woo Chun, Contributions of jellyfish fertilizer to survival and growth of seedlings planted in a recently burned forest, Republic of Korea, Journal of the Faculty of Agriculture, Kyushu University, 59, 1, 181-189, 2014.02.
53. Yoshinori Shinohara, Tomonori Kume, Ryuji Ichihashi, Hikaru Komatsu, Kyoichi Otsuki, Moso-bamboo forests in Japan
What are the effects of their area expansion on ecosystem services?, Nihon Ringakkai Shi/Journal of the Japanese Forestry Society, 96, 6, 351-361, 2014.01.
54. Takami Saito, Hiroki Matsuda, Misako Komatsu, Yang Xiang, Atsuhiro Takahashi, Yoshinori Shinohara, Kyoichi Otsuki, Forest canopy interception loss exceeds wet canopy evaporation in Japanese cypress (Hinoki) and Japanese cedar (Sugi) plantations, Journal of Hydrology, 10.1016/j.jhydrol.2013.09.053, 507, 287-299, 2013.12.
55. Masaaki Chiwa, Tsutomu Enoki, Naoko Higashi, Tomo'Omi Kumagai, Kyoichi Otsuki, The increased contribution of atmospheric nitrogen deposition to nitrogen cycling in a rural forested area of Kyushu, Japan, Water, Air, and Soil Pollution, 10.1007/s11270-013-1763-2, 224, 11, 2013.11, Japan has been receiving increasing levels of atmospheric nitrogenous pollutants from the East Asian continent over the last few decades, so it is critical to evaluate the impact of this increased atmospheric nitrogen (N) deposition on N cycling even in rural forests. This study evaluated the contribution of the current level of atmospheric N deposition to N cycling in a rural forested area. Bulk precipitation and stream water were collected during 2007-2011 at the Shiiba Research Forest (SRF) located in the central Kyushu mountain range of southern Japan. Litterfall was also collected to investigate the contribution of atmospheric N deposition to total N input (litterfall N + atmospheric N deposition). The results showed that atmospheric depositions of both nitrate (NO3 -) and ammonium (NH4 +) were a few times higher during 2009-2011 than in 1991. This could be the result of additional N deposition from the increased long-range transport of nitrogenous pollutants from the East Asian continent. The current level of annual N deposition (9.7 kg N ha-1 year-1) at the SRF was comparable with that at many urban sites and was close to the reported threshold values causing N saturation in forest ecosystems. Although current atmospheric N deposition was an important component (23 %) of total N input (43 kg N ha -1 year-1) at the SRF, the concentrations of NO 3 - in stream water were consistently low (<10 μmol L-1). These results indicate that atmospheric N deposition is currently largely incorporated into forest ecosystems without excess N export from forested watersheds..
56. Byoungkoo Choi, Jeff A. Hatten, Janet C. Dewey, Kyoichi Otsuki, Dusong Cha, Effect of timber harvesting on stormflow characteristics in headwater streams of managed, forested watersheds in the upper gulf coastal plain of Mississippi, Journal of the Faculty of Agriculture, Kyushu University, 58, 2, 395-402, 2013.09, Headwater streams are crucial parts of overall watershed dynamics because they comprise more than 50-80% of stream networks and watershed land areas. This study addressed the influence of headwater areas (ephemeral and intermittent) on stormflow characteristics following harvest within three first-order catchments in the Upper Gulf Coastal Plain of Mississippi. Four treatments including two Best Management Practices (BMPs) were applied: BMP1 - removal of all merchantable stems while leaving understory intact with minimum surface soil disturbance; BMP2 - same as BMPl with the addition of logging debris to the drainage channel; Clearcut - total harvest with no BMPs applied; Reference - left uncut as a control. Following harvesting, the increase in water table depth ranged from 1.6 cm in BMPl to 28.2 cm in the clearcut treatment during 2008, and from 10.5 cm in BMPl to 54.2 cm in BMP2 during 2009. However, impacts of timber harvesting on peak discharge, storm discharge, and time of concentration were not consistent with water table response. Response time to stormflow was reduced significantly in harvested treatments (BMP2 and unrestricted harvest) probably as a result of decreased evapotranspiration and increased soil disturbance..
57. Yanna Xiong, Guoqiang Wang, Yanguo Teng, Kyoichi Otsuki, Modeling the impacts of land use changes on soil erosion at the river basin scale, Journal of the Faculty of Agriculture, Kyushu University, 58, 2, 377-387, 2013.09, The potential for soil erosion is strongly affected by land use. A proper modeling approach should be selected to explicitly assess the impacts of land use changes on soil erosion at a river basin scale. The reliability of simulation results from erosion models is circumscribed by considerable spatial variation in many parameters. In this study, a grid-based distributed soil erosion and sediment transport model was used in conjunction with a laboratory rainfall simulation experiment to determine the impact of land use changes on soil erosion and sediment yield in a river basin during individual storms. Land use changes in the Lushi Basin, primarily in Henan, China, were analyzed by comparing the historical land use maps in 1990 and 1995. Through comparing the results for four selected storms that were compiled using these two land use maps, it was found that the average erosion rates increased from 1989 to 1996. The increase in average erosion rates followed the land use changes, especially the transformation of forest to farmland. The results indicated that even slight land use change, from forest to farmland or vice versa, had a significant effect on regional soil erosion rates and sediment supply to rivers..
58. Young Sang Ahn, Kyoichi Otsuki, Soung Ryoul Ryu, Kun Woo Chun, Ki Wan An, Kye Han Lee, Hyung Tae Choi, Shigeru Mizugaki, Jung Il Seo, Surface erosion control by control by felled log erosion barriers in post fire areas in eastern coastal regions of the republic of Korea, Journal of the Faculty of Agriculture, Kyushu University, 58, 2, 389-394, 2013.09, Recently, large forest fires have occurred along the Baekdu mountain range in the eastern coastal regions of the Republic of Korea. The turbidity of water in streams increased substantially after the forest fires, leading to substantial deterioration in the water quality. Residents living near the burned areas have requested remediation measures to reduce the turbidity in streams during rainfall events. Our research was conducted at the locations affected by the Donghaean fire in 2000 to investigate: 1) the influence of forest fires on the physical properties of the soil and 2) the effectiveness of contour-felled log erosion barriers (CFLEBs) in reducing surface soil erosion. The CFLEBs is a remediation technique in which felled burnt trees are laid along the ground contour to promote water infiltration into the soil and to reduce the movement of sediment by decreasing the amount of surface runoff. The results showed that the bulk density of the surface soils in the burned areas was greater than that in the unburned areas, and that the mesopore ratio of the surface soils in the burned areas was less than that in the unburned areas. These results implied that forest fires damaged the physical structure of the surface soil and made the surface soil more vulnerable to post-fire runoff and hillslope erosion. The slope lysimeter experiments conducted over two years from May 2010 to June 2012 showed that the annual average sediment yields were 17.8 g m-2 yr-1 in areas treated with CFLEBs and 133.6 g m-2 yr -1 in areas not treated with CFLEBs. These results demonstrate that CFLEBs are an effective measure for controlling surface soil erosion and thus reducing turbidity in streams. Since burnt trees are often cut down in the Republic of Korea after forest fires to prevent the spread of damage caused by insects epidemics, the construction of CFLEBs from already felled trees would be an economically and ecologically useful method to reduce surface soil erosion and turbidity in streams over large scales..
59. Komatsu H, Kume T, Otsuki K, Sensitivity of annual runoff to interannual precipitation variations for forested catchments in Japan., Hydrological Research Letters, 2013.07.
60. Ayumi Katayama, Tomonori Kume, Hikaru Komatsu, Taku M. Saitoh, Mizue Ohashi, Michiko Nakagawa, Masakazu Suzuki, Kyoichi Otsuki, Tomo'omi Kumagai, Carbon allocation in a Bornean tropical rainforest without dry seasons, Journal of Plant Research, 10.1007/s10265-012-0544-0, 126, 4, 505-515, 2013.07, To clarify characteristics of carbon (C) allocation in a Bornean tropical rainforest without dry seasons, gross primary production (GPP) and C allocation, i.e., above-ground net primary production (ANPP), aboveground plant respiration (APR), and total below-ground carbon flux (TBCF) for the forest were examined and compared with those from Amazonian tropical rainforests with dry seasons. GPP (30.61 MgC ha-1 year-1, eddy covariance measurements; 34.40 MgC ha-1 year-1, biometric measurements) was comparable to those for Amazonian rainforests. ANPP (6.76 MgC ha-1 year-1) was comparable to, and APR (8.01 MgC ha-1 year-1) was slightly lower than, their respective values for Amazonian rainforests, even though aboveground biomass was greater at our site. TBCF (19.63 MgC ha-1 year-1) was higher than those for Amazonian forests. The comparable ANPP and higher TBCF were unexpected, since higher water availability would suggest less fine root competition for water, giving higher ANPP and lower TBCF to GPP. Low nutrient availability may explain the comparable ANPP and higher TBCF. These data show that there are variations in C allocation patterns among mature tropical rainforests, and the variations cannot be explained solely by differences in soil water availability..
61. Yoshinori Shinohara, Hikaru Komatsu, Kohei Kuramoto, Kyoichi Otsuki, Characteristics of canopy interception loss in Moso bamboo forests of Japan, Hydrological Processes, 10.1002/hyp.9359, 27, 14, 2041-2047, 2013.07, In recent years, Moso bamboo (Phyllostachys pubescens) forests have rapidly expanded in Japan by replacing surrounding coniferous and/or broadleaved forests. To evaluate the change in water yield from forested areas because of this replacement, it is necessary to examine evapotranspiration for Moso bamboo forests. However, canopy interception loss, one of the major components of evapotranspiration in forested areas, has been observed in only two Moso bamboo forests in Japan with relatively high stem density (~7000 stems/ha). There are, in fact, many Moso bamboo forests with much lower stem density. Thus, we made precipitation (Pr), throughfall (Tf) and stemflow (Sf) observations for 1 year in a Moso bamboo forest with stem density of 3611 stems/ha and quantified canopy interception loss (Ic). Pr and Ic for the experimental period were 1636 and 166 mm, respectively, and Ic/Pr was 10%. The value was approximately the same as values for the other two Moso bamboo forests and lower than values for coniferous and broadleaved forests. On the other hand, Tf/Pr and Sf/Pr for our forest (86% and 4%, respectively) were approximately 10% of Pr larger and smaller than values for the other two Moso bamboo forests. These results suggest that the difference in stem density greatly affects precipitation partitioning (i.e. Tf/Pr and Sf/Pr) but does not greatly change Ic/Pr..
62. Shinohara Y, Tsuruta K, Akira Ogura, Fumikazu Noto, Komatsu H, Otsuki K, Toshisuke Maruyama, Azimuthal and radial variations in sap flux density and effects on stand-scale transpiration estimates in a Japanese cedar forest, Tree Physiology, 10.1093/treephys/tpt029, 33, 5, 550-558, 2013.05.
63. Yoshinori Shinohara, Kenji Tsuruta, Tomonori Kume, Kyoichi Otsuki, An overview of stand-scale transpiration measurements using the sap flow technique for evaluating the effects of forest management practices on transpiration, Nihon Ringakkai Shi/Journal of the Japanese Forestry Society, 95, 6, 321-331, 2013.01, Recently, securing water resources has become one of the major purposes of forest management in Japan; this is done by thinning in coniferous plantations, replacing coniferous plantations with broadleaved forests, and conducting clearing or thinning operations in bamboo forests to reduce water loss to evapotranspiration. However, the effects of forest management practices on water resources have not been fully clarified because of a lack of evapotranspiration data from Japanese forests. Transpiration is a primary component of evapotranspiration in forested areas. We presented an overview of transpiration measurements based on the sap flow technique, a typical method used for measuring transpiration, to contribute to the accumulation of transpiration data for Japanese forests. Firstly, we compared the sap flow technique with other transpiration measurement methods and showed the usefulness of the sap flow technique for examining the effect of forest management practices on transpiration. Secondly, we explained the scaling-up procedures needed to up-scale from measures of sap flux densities to individual tree-scale transpiration and from individual tree-scale transpiration to stand-scale transpiration. Finally, we summarized stand-scale transpiration measurements based on the sap flow techniques as used in Japan, and recommend the types of forests which should be measured to help land and water managers have an informed discussion related to modifying forest management with the goal of securing water resources by forest practices. Measurements of transpiration are needed from larch plantations, broadleaved forests, and bamboo forests in Japan. Transpiration data measured in Japanese cedar and Japanese cypress plantations at ages of more than 60 years and less than 20 years would also be useful for the discussion..
64. Masaaki Chiwa, Tomotaka Uemura, Kyoichi Otsuki, Hiroshi Sakugawa, Characteristics of nitrogenous air pollutants at urban and suburban forested sites, Western Japan, Water, Air, and Soil Pollution, 10.1007/s11270-012-1294-2, 223, 8, 5473-5481, 2012.09, Nitrogenous air pollutants including nitrogen dioxide (NO 2), nitric acid (HNO 3), nitrate (NO 3 -), ammonia (NH 3), ammonium (NH 4 +), and nitrous acid (HONO) were characterized at an urban forested (UF) site in Hiroshima and at a suburban forested (SF) site in Fukuoka, western Japan, using an annular denuder system for 1 year from May 2006 to May 2007 to compare the concentrations and chemical species of atmospheric nitrogenous pollutants between UF and SF sites. The proximity of the urban area was reflected in higher NO 2 concentrations at the UF site than at the SF site. NO 2 was more oxidized at the SF site because it is farther from an urban area than the UF site, which was reflected in higher concentrations of HNO 3 at the SF site than the UF site. HNO 3 and acidic sulfate is neutralized by NH 3, existing as ammonium nitrate (NH 4NO 3) and ammonium sulfate [(NH 4) 2SO 4] at the UF site. At the SF site, acidic sulfate is neutralized by NH 3, existing as (NH 4) 2SO 4, but NH4NO3, had scarcely formed at the SF site. A much higher HONO concentration was observed at the UF site than at the SF site, especially in winter and spring at night, which could be explained by higher NO 2 concentrations at the UF site because of its proximity to an urban area and stagnant meteorological conditions. Atmospheric HONO determination was critical in evaluating the possibility of damage to trees in UF areas..
65. Jun'Ichiro Ide, Masaaki Chiwa, Naoko Higashi, Ryoko Maruno, Yasushi Mori, Kyoichi Otsuki, Determining storm sampling requirements for improving precision of annual load estimates of nutrients from a small forested watershed, Environmental Monitoring and Assessment, 10.1007/s10661-011-2299-9, 184, 8, 4747-4762, 2012.08, T'his study sought to determine the lowest number of storm events required for adequate estimation of annual nutrient loads from a forested watershed using the regression equation between cumulative load (ΣL) and cumulative stream discharge (ΣQ). Hydrological surveys were conducted for 4 years, and stream water was sampled sequentially at 15-60-min intervals during 24 h in 20 events, as well as weekly in a small forested watershed. The bootstrap sampling technique was used to determine the regression (ΣL-ΣQ) equations of dissolved nitrogen (DN) and phosphorus (DP), particulate nitrogen (PN) and phosphorus (PP), dissolved inorganic nitrogen (DIN), and suspended solid (SS) for each dataset of ΣL and ΣQ. For dissolved nutrients (DN, DP, DIN), the coefficient of variance (CV) in 100 replicates of 4-year average annual load estimates was below 20% with datasets composed of five storm events. For particulate nutrients (PN, PP, SS), the CV exceeded 20%, even with datasets composed of more than ten storm events. The differences in the number of storm events required for precise load estimates between dissolved and particulate nutrients were attributed to the goodness of fit of the ΣL-ΣQ equations. Bootstrap simulation based on flow-stratified sampling resulted in fewer storm events than the simulation based on random sampling and showed that only three storm events were required to give a CV below 20% for dissolved nutrients. These results indicate that a sampling design considering discharge levels reduces the frequency of laborious chemical analyses of water samples required throughout the year..
66. Xue Baolin, Hikaru Komatsu, Tomo'omi Kumagai, Ayumi Kotani, kyoichi otsuki, Takeshi Ohta, Interannual variation of evapotranspiration in an eastern Siberian larch forest, HYDROLOGICAL PROCESSES, 10.1002/hyp.9195, 26, 15, 2360-2368, 2012.07.
67. Hikaru Komatsu, Yuka Onozawa, Tomonori Kume, Kenji Tsuruta, Yoshinori Shinohara, Kyoichi Otsuki, Canopy conductance for a Moso bamboo (Phyllostachys pubescens) forest in western Japan, Agricultural and Forest Meteorology, 10.1016/j.agrformet.2012.01.004, 156, 111-120, 2012.04, In western Japan, Moso bamboo (Phyllostachys pubescens) forests have been expanding by replacing surrounding forests (e.g., coniferous plantation forests), which raises concerns about possible changes in terrestrial water and carbon cycles. Canopy conductance (G c) is a critical parameter for determining canopy transpiration and photosynthesis. To clarify the characteristics of G c for Moso bamboo forests, we calculated G c during a growing season for a Moso bamboo forest on the basis of canopy transpiration measurements made using the sap-flux method, and then compared the G c value with values for coniferous plantation forests in western Japan. G c was primarily related to the vapor pressure deficit and secondarily to solar radiation, similar to the results obtained for other temperate forests. Under light-saturated conditions, G c for the bamboo forest was approximately twice that for the coniferous plantation forests despite the lower leaf area index for the bamboo forest. This implies higher canopy transpiration and photosynthesis for the bamboo forest, and therefore possible changes in terrestrial water and carbon cycles due to the replacement of coniferous plantation forests by bamboo forests..
68. Tomonori Kume, Kyoichi Otsuki, Sheng Du, Norikazu Yamanaka, Yi Long Wang, Guo Bin Liu, Spatial variation in sap flow velocity in semiarid region trees
Its impact on stand-scale transpiration estimates, Hydrological Processes, 10.1002/hyp.8205, 26, 8, 1161-1168, 2012.04, In this study, we aimed to clarify spatial variations in xylem sap flow, and to determine the impacts of these variations on stand-scale transpiration (E) estimates. We examined circumferential and radial variations in sap flow velocity (F d) measured at several directions and depths in tree trunks of black locust (Robinia pseudoacacia) and native oak (Quercus liaotungensis), both of which have ring-porous wood anatomy, in forest stands on the Loess Plateau, China. We evaluated the impacts of circumferential variations in F d on stand-scale transpiration estimates using a simple scaling exercise. We found significant circumferential variations in F d in the outermost xylem in both species (coefficients of variation = 20-45%). For both species, F d measured at the inner xylem was smaller than that of the outermost xylem and the F d at the depth of > 10 mm was almost zero. The simple exercises showed that omitting circumferential variations in F d affected the E estimate by 16-21%, which was less than the effects of omitting within-tree radial and tree-to-tree variations in F d in both species. These results suggest that circumferential variations in F d can be a minor source of error for E estimates compared with within-tree radial and tree-to-tree variations in F d, regardless of the significant circumferential variations..
69. Guoqiang Wang, Jing Song, Bao Lin Xue, Xinyi Xu, Kyoichi Otsuki, Land use and land cover Cchange of hulun lake nature reserve in inner Mongolia,China
A Modeling analysis, Journal of the Faculty of Agriculture, Kyushu University, 57, 1, 219-225, 2012.02, Based on three-year remote sensing data and cellular automata (CA)-Markov model, this study analyzed the temporal and spatial variation features of land use and land cover change in Hulun Lake Nature Reserve from 1999 to 2007. The result indicated that during the period between 1999 and 2007, there had been relatively great changes in land use type in Hulun Lake Nature Reserve, with ecological problems such as grassland degradation and water area shrinkage, becoming increasingly serious. Via analyzing the area variations of various land use types and the historical statistics of Hulun Lake's water level during this period, the study found that the water use of the upstream by the population pressure and economy development might be related with the decline in Hulun Lake's water levels which caused the increase in the sandy area. This kind of information is necessary for the land management of the area and will help in the ecosystem conservation in future..
70. Hikaru Komatsu, Jaeil Cho, Kazuho Matsumoto, Kyoichi Otsuki, Simple modeling of the global variation in annual forest evapotranspiration, Journal of Hydrology, 10.1016/j.jhydrol.2011.12.030, 420-421, 380-390, 2012.02, Annual forest evapotranspiration (ET) is highly variable among various sites. Zhang's model (Zhang et al., 2001) has been widely used for predicting the spatial variation in ET. The forest component of the model employs limiting theory and assumes constant annual potential evaporation (E 0=1410mm) by regressing data recorded at 56 forest sites. However, most of the data used in determining E 0 were recorded for limited regions (Australia, African countries, and the United States). We summarized 829 forest ET data items obtained for sites around the world from earlier publications. Using the dataset, we showed that Zhang's model overestimates forest ET in temperate and boreal regions with low annual mean temperature (T) owing to the E 0 value. We revised the E 0 term of Zhang's model so as to consider the dependency of E 0 on T using the dataset. The revised model did not overestimate forest ET in temperate and boreal regions. Consequently, we recommend revising the E 0 term of Zhang's model when predicting forest ET in these regions..
71. Jaeil Cho, Taikan Oki, Pat J.F. Yeh, Wonsik Kim, Shinjiro Kanae, Kyoichi Otsuki, On the relationship between the Bowen ratio and the near-surface air temperature, Theoretical and Applied Climatology, 10.1007/s00704-011-0520-y, 108, 1-2, 135-145, 2012.01, The sensitivity of land surface energy partitioning to near-surface air temperature (Ta) is a critical issue to understand the interaction between land surface and climatic system. Thus, studies with in situ observed data compiled from various climates and ecosystems are required. The relations derived from such empirical analyses are useful for developing accurate estimation methods of energy partitioning. In this study, the effect of Ta on land surface energy partitioning is evaluated by using flux measurement data compiled from a global network of eddy covariance tower sites (FLUXNET). According to the analysis of 25 FLUXNET sites (60 site-years) data, the Bowen ratio is found to have a linear relation with the bulk surface resistance normalized by aerodynamic and climatological resistance parameters in general, of which the slope and intercept are dependent on Ta. Energy partitioning in warmer atmosphere is less sensitive to changes in land surface conditions. In addition, a negative relation is found between Bowen ratio and Ta, and this relation is stronger above less vegetated surface and under low vapor pressure deficit and low received radiative energy condition. The empirical results obtained in this study are expected to be useful in gaining better understanding of alternating surface energy partitioning under increasing Ta..
72. Yoshiyuki Miyazawa, Makiko Tateishi, Hikaru Komatsu, Tomo'omi Kumagai, Kyoichi Otsuki, Are measurements from excised leaves suitable for modeling diurnal patterns of gas exchange of intact leaves?, Hydrological Processes, 10.1002/hyp.8107, 25, 18, 2924-2930, 2011.08, To examine the feasibility of using ecophysiological data from excised leaves for a meteorological simulation model of gas exchange, we compared the obtained gas exchange rates and the modelled ones using excised leaves and those using intact leaves. Instantaneous gas exchange rates of excised leaves and stomatal control in response to environmental conditions were not significantly different from those of attached leaves. Modelled gas exchange rates based on excised leaf data showed a good fit to the diurnal patterns of in situ measurements. This suggests that use of excised leaf data to predict gas exchange of intact leaves is permissible as long as the effects of excision are pre-screened as described in this paper..
73. Hikaru Komatsu, Yoshinori Shinohara, Tomonori Kume, Kyoichi Otsuki, Changes in peak flow with decreased forestry practices
Analysis using watershed runoff data, Journal of Environmental Management, 10.1016/j.jenvman.2011.01.010, 92, 6, 1528-1536, 2011.06, The prevalence of forestry practices such as thinning and pruning have gradually decreased since the 1980s. Researchers have noted an increased flood risk with decreased forestry practices for coniferous plantations in Japan on the basis of infiltration and overland flow measurements at a plot scale (typically several square meters). However, no studies have examined changes in peak flow with decreased forestry practices at a watershed scale (typically several tens or hundreds of square kilometers) even though flood disasters generally occur at this scale in Japan. We examined changes in frequency distributions of daily precipitation (P) and runoff (Q) during the period 1979-2007 at the Terauchi watershed, where forestry practices are known to have decreased. For this purpose, we divided P and Q data into 14 and 15 classes according to the magnitude, respectively, and examined changes in the frequency for each class during the period. We observed no significant increasing trend for any P or Q class. Even when taking into account the effect of interannual variations in precipitation on the frequency for each Q class, there was no significant increasing trend in the frequencies except for two Q classes with moderate Q values. These results suggest that the increase in flood risk due to decreased forestry practices might be less than expected..
74. Toshihiro Umebayashi, Kenji Fukuda, Tomoyuki Haishi, Ryo Sotooka, Sule Zuhair, Kyoichi Otsuki, The developmental process of xylem embolisms in pine wilt disease monitored by multipoint imaging using compact magnetic resonance imaging, Plant physiology, 10.1104/pp.110.170282, 156, 2, 943-951, 2011.06, In pine wilt disease (PWD), embolized tracheids arise after virulent pine wood nematodes (PWN), Bursaphelenchus xylophilus, invade the resin canal of pine tree; infected pine trees finally die from significant loss of xylem water conduction. We used a compact magnetic resonance imaging system with a U-shaped radio frequency (rf) probe coil to reveal the developmental process of the xylem dysfunction in PWD. Multiple cross-sectional slices along the stem axis were acquired to periodically monitor the total water distribution in each 1-year-old main stem of two 3-year-old Japanese black pines (Pinus thunbergii) after inoculation of PWN. During the development of PWD, a mass of embolized tracheids around the inoculation site rapidly enlarged in all directions. This phenomenon occurred before the significant decrease of water potential. Some patch-like embolisms were observed at all monitoring positions during the experimental period. Patchy embolisms in a cross-section did not expand, but the number of patches increased as time passed. When the significant decrease of water potential occurred, the xylem dysfunctional rate near the inoculation point exceeded 70%. Finally, almost the whole area of xylem was abruptly embolized in all cross-sections along the stem. This phenomenon occurred just after water conduction was mostly blocked in one of the cross-sections. Thus, it appears that the simultaneous expansion of embolized conduit clusters may be required to induce a large-scale embolism across the functional xylem. Consequently, xylem dysfunction in infected trees may be closely related to both the distribution and the number of PWN in the pine stem..
75. Miyazawa, Y., Tateishi, M., Komatsu, H., Kumagai, T. and Otsuki, K., Are measurements from excised leaves suitable for modeling diurnal patterns of gas exchange of intact leaves?, Hydrological Processes, 25, 10, 2011.05, [URL].
76. Xue B, Kumagai T, Iida S, Nakai T, Matsumoto K, Komatsu H, Otsuki K, Ohta T, Influences of canopy structure and physiological traits on flux partitioning between understory and overstory in an eastern Siberian boreal larch forest, Ecological Modelling, 10.1016/j.ecolmodel.2011.01.021, 222, 8, 1479-1490, 2011.04, [URL].
77. Xiaohua Wei, Ge Sun, James M. Vose, Kyoichi Otsuki, Zhiqiang Zhang, Keith Smetterm, Forest ecohydrological processes in a changing environment, Ecohydrology, 10.1002/eco.218, 4, 2, 143-145, 2011.03, The papers in this issue are a selection of the presentations made at the second International Conference on Forests and Water in a Changing Environment. This special issue 'Forest Ecohydrological Processes in a Changing Environment' covers the topics regarding the effects of forest, land use and climate changes on ecohydrological processes across forest stand, watershed and regional spatial scales..
78. James M. Vose, Ge Sun, Chelcy R. Ford, Michael Bredemeier, Kyoichi Otsuki, Xiaohua Wei, Zhiqiang Zhang, Lu Zhang, Forest ecohydrological research in the 21st century
What are the critical needs?, Ecohydrology, 10.1002/eco.193, 4, 2, 146-158, 2011.03, Modern ecohydrologic science will be critical for providing the best information to policy makers and society to address water resource challenges in the 21st century. Implicitly, ecohydrology involves understanding both the functional interactions among vegetation, soils, and hydrologic processes at multiple scales and the linkages among upland, riparian, and aquatic components. In this paper, we review historical and contemporary ecohydrologic science, focusing on watershed structure and function and the threats to watershed structure and function. Climate change, land use change, and invasive species are among the most critical contemporary issues that affect water quantity and quality, and a mechanistic understanding of watershed ecosystem structure and function is required to understand their impacts on water quantity and quality. Economic and social values of ecosystem services such as water supply from forested watersheds must be quantified in future research, as land use decisions that impact ecohydrologic function are driven by the interplay among economic, social, political, and biological constraints. Future forest ecohydrological research should focus on: (1) understanding watershed responses to climate change and variability, (2) understanding watershed responses to losses of native species or additions of non-native species, (3) developing integrated models that capitalize on long-term data, (4) linking ecohydrologic processes across scales, and (5) managing forested watersheds to adapt to climate change. We stress that this new ecohydrology research must also be integrated with socio-economic disciplines. Published in 2011. This article is a US Government work and is in the public domain in the USA. This article is a US Government work and is in the public domain in the USA. Published in 2011 by John Wiley & Sons, Ltd..
79. Guoqiang Wang, Baolin Xue, Xiangshan Xue, Jingshan Yu, Kyoichi Otsuki, Continuous modeling of infiltration rate for the management of sprinkler irrigation, Journal of the Faculty of Agriculture, Kyushu University, 56, 1, 157-161, 2011.02, The spatially and temporally variable characteristics of soil infiltration process are a major physical constraint for the irrigated lands to achieve higher irrigation efficiencies. Substantial works have been directed towards developing state-dependent models to estimate the infiltration characteristics of soils, which are not suitable for continuous simulation of the infiltration process under complex rainfall or irrigation intensities. In this study, the time compression approximation (TCA) method is coupled with the Philip's infiltration equation, and the coupled infiltration model is extended beyond the ponding time to estimate the postponding infiltration process. An offset time is then introduced into the coupled infiltration model for solving the problems caused by the necessities of refreshing the state-dependent variables stepwisely. This simplifies the determination processes of the model's variables and amplifies its applicability under complex rainfall or irrigation intensities. By using the soil expA(c)rimental data, the TCA based infiltration model shows good performance in predicting the cumulative infiltration. The deviation coefficients of the infiltration predictions range from 0.59% to 34.74%, and the Nash coefficient of efficiency is calculated to be 82% for all the simulated results. This suggests that the proposed TCA based infiltration model could be suitable for the management of sprinkler irrigation..
80. Guoqiang Wang, Baolin Xue, Jingshan Yu, Kyoichi Otsuki, Estimating the agricultural water productivity of the yellow river basin based on remote sensing data, Journal of the Faculty of Agriculture, Kyushu University, 56, 1, 149-156, 2011.02, Water shortage for agricultural water use is a major problem m the Yellow River basin. I his research use NDVI value, meteorological data, supervised classification in remote sensing image and actual statistical data to estimate and verify the wheat and maize distribution and the relevant crop water productivity values in the Yellow River basin. The validation of the method is performed by comparing the results with the distribution of CIESIN statistic data for 1990. To obtain the accurate crop water productivity, the study used and compared two methods for calculating the total crop water productivity. The first one is to sum the crop water productivity calculated by multiplying the crop water requirement per unit area and the estimated planting total area of crops in the basin. The second one is to sum the crop water productivity calculated for each province. The research found that the remote sensing data could efficiently improve the accuracy in estimating the crop water productivity..
81. Komatsu, H., Kume, T. and Otsuki, K., Increasing annual runoff-broadleaf or coniferous forests ?, Hydrological Processes, 10.1002/hyp.7898, 25, 2, 302-318, 2011.01.
82. Kenji Tsuruta, Tomonori Kume, Hikaru Komatsu, Naoko Higashi, Toshihiro Umebayashi, Tomo'omi Kumagai, Kyoichi Otsuki, Azimuthal variations of sap flux density within Japanese cypress xylem trunks and their effects on tree transpiration estimates, Journal of Forest Research, 10.1007/s10310-010-0202-0, 15, 6, 398-403, 2010.12, Sap flow techniques are practical tools for estimating tree transpiration. Though many previous studies using sap flow techniques did not consider azimuthal variations of sap flux density (Fd) on xylem trunk to estimate tree transpiration, a few studies reported that ignoring the azimuthal variations in Fd could cause large errors in tree transpiration estimates for some tree species. Therefore, examining azimuthal variations in Fd for major plantation tree species is critical for estimating tree transpiration. Using the thermal dissipation method, we examined azimuthal variations in Fd in six trees of Japanese cypress Chamaecyparis obtusa (Sieb. et Zucc.) Endl., which is one of the most common plantation tree species in Japan. We recorded considerable variations among Fd at four different azimuthal directions. The Fd value for one aspect was more than 100% larger than those for the other aspects. We calculated differences between tree transpiration estimates based on Fd for one to three azimuthal directions and those based on Fd for four aspects. The differences relative to tree transpiration estimates based on Fd for four aspects were typically 30, 20, and 10% in accordance with the Fd for one, two, and three measurement aspects, respectively. This finding indicates that ignoring azimuthal variations could cause large errors in tree transpiration estimates for Japanese cypress..
83. Jaeil Cho, Pat J.F. Yeh, Yang Won Lee, Hyungjun Kim, Taikan Oki, Shinjiro Kanae, Wonsik Kim, Kyoichi Otsuki, A study on the relationship between Atlantic sea surface temperature and Amazonian greenness, Ecological Informatics, 10.1016/j.ecoinf.2010.05.005, 5, 5, 367-378, 2010.09, The growth of tropical rainforest in Amazon is critically vulnerable to the change in rainfall and radiation than in temperature, and that amount of rainfall and cloudiness in the northeast region of South American is strongly affected by the Atlantic sea surface temperature (SST). Results from recent model experiments for future climate projection have indicated a reduction of Amazonian greenness by a weakening of tropical vapor circulation system related with the change in SST. Therefore, the observational investigation of the relations between the Amazon greenness and Atlantic SST is fundamental to understand the response of Amazonian tropical forest to climate change. In this study, the effect of Atlantic SST on the spatial and temporal change of the Normalized Difference Vegetation Index (NDVI) in the Amazonian region is examined by using satellite remote sensing data for the period of 1981-2001. A strong correlation between NDVI and SST is found for certain regions in Amazon during the periods of 1980s and 1990s, respectively. In addition, strong correlations with NDVI lagging behind SST for two months and one year, respectively, are also identified from the interannual December-to-February (rain season) variations during 1981-2001. Despite these findings, the mechanisms behind the identified correlation remain unclear. Further analyses using observed precipitation and radiation data are required to understand the potential changes of Amazonian rainforest in the context of global warming..
84. Masaaki Chiwa, Yuka Onozawa, Kyoichi Otsuki, Hydrochemical characteristics of throughfall and stemflow in a Moso-bamboo (Phyllostachys pubescens) forest, Hydrological Processes, 10.1002/hyp.7706, 24, 20, 2924-2933, 2010.09, To investigate the impacts of the invasion by bamboo on fluxes of nutrients and pollutants, the nutrient/pollutant fluxes and canopy interactions, including neutralization of acidity, leaching and uptake of nitrogen (N), were characterized in conjunction with rainfall partitioning in a Moso-bamboo (Phyllostachys pubescens) forest. Measurements of precipitation volume, pH, major ions, and silicate (SiO2) in rainfall, throughfall and stemflow were collected weekly in a Moso-bamboo forest located in Munakata City, Western Japan for 1 year. Results showed that rainfall partitioning into stemflow was larger than that for other types of forest, which may be due to the properties of Moso-bamboo forest structure, such as a straight and smooth culm. Inorganic N (NO3- + NH4+) and S (SO42-) fluxes of throughfall and stemflow were approximately 1.6 and 1.3 times higher than that of rainfall, respectively. Contribution of stemflow flux to inorganic N and S fluxes to the forest floor was high. This could be due to lower uptake of inorganic N through culm and a higher rainfall partitioning into stemflow than that for other types of forest. The Moso-bamboo canopy neutralized rainfall acidity, reducing the fluxes of potentially acidifying compounds via throughfall and stemflow. Canopy leaching of K+ was distinctly higher than that of Mg2+ and Ca2+ and could be related to the high mobility of K+ in plant tissues. Cl- and SiO2 were readily leached as for K+. The impact of the invasion by bamboo on nutrient cycling was discussed..
85. Hikaru Komatsu, Yuka Onozawa, Tomonori Kume, Kenji Tsuruta, Tomo'omi Kumagai, Yoshinori Shinohara, Kyoichi Otsuki, Stand-scale transpiration estimates in a Moso bamboo forest
II. Comparison with coniferous forests, Forest Ecology and Management, 10.1016/j.foreco.2010.06.040, 260, 8, 1295-1302, 2010.09, In western Japan, Moso bamboo (Phyllostachys pubescens) forests have been expanding by replacing surrounding vegetation such as coniferous plantation forests and natural broadleaved forests. It has been speculated that the replacement of surrounding vegetation by bamboo forests could alter the vegetation water cycle and available water resources. We quantified stand-scale transpiration (E) in a bamboo forest on the basis of sap-flux measurements and compared the E value with values for coniferous forests. The annual E was estimated to be 567 mm. Seasonal trends in E primarily corresponded to seasonal trends in the vapor pressure deficit. Annual E for the bamboo forest was higher than that for the coniferous forests by 12% of annual precipitation (P). This difference in annual E is comparable with the difference in annual interception evaporation (I) relative to P between bamboo and coniferous forests; previous studies reported lower I for bamboo forests by ∼10% of P. Thus, the sum of E and I was comparable for bamboo and coniferous forests. As this study is the first measuring E of bamboo forests, further studies are required to examine the generality of our results..
86. Tomonori Kume, Yuka Onozawa, Hikaru Komatsu, Kenji Tsuruta, Yoshinori Shinohara, Toshihiro Umebayashi, Kyoichi Otsuki, Stand-scale transpiration estimates in a Moso bamboo forest
(I) Applicability of sap flux measurements, Forest Ecology and Management, 10.1016/j.foreco.2010.07.012, 260, 8, 1287-1294, 2010.09, The applicability of sap flux (Fd) measurements to bamboo forests has not been studied. This study was undertaken to establish an optimal and effective design for stand-scale transpiration (E) estimates in a Moso bamboo forest. To this aim, we validated Fd measurements in Moso bamboos in a cut bamboo experiment. In addition, we analyzed how sample sizes affect the reliability of E estimates calculated from Fd and conducting culm area (AS_b). In the cut bamboo experiments, we found that Fd measurement using a 10mm probe was a valid means of determining the water-use behavior of a Moso bamboo, although a specific correction was needed. Furthermore, we calculated E from stand AS_b (AS_stand) and mean stand Fd (JS). Employing Monte Carlo analysis, we examined potential errors associated with sample size in E, AS_stand, and JS using an original dataset with AS_b and Fd measured for 40 and 16 individuals, respectively. Consequently, we determined the optimal sample size for both AS_stand and JS estimates as 11. The optimal sample sizes for JS were almost the same under different vapor pressure deficit and soil moisture conditions. The optimal sample size for JS at the study site was less than that of a coniferous plantation in the same region probably owing to small individual-to-individual variations in sap flux in the Moso bamboo forest. Our study concludes that sap flux measurements are an applicable technique for assessing water use in Moso bamboo forests..
87. Komatsu H, Kume T, Shinohara Y, Miyazawa Y, Otsuki K, Did annual runoff and low flow decrease with reduced forestry practices in Japan?, Hydrological Processes, 24, 2440-2451, 2010.08.
88. Wang YL, Liu GB, Kume T, Otsuki K, Yamanaka N,Du S, Estimating water use of a black locust plantation by the thermal dissipation probe method in the semiarid region of Loess Plateau, China, Journal of Forest Research, 10.1007/s10310-010-0184-y, 15, 4, 241-251, 2010.08, [URL].
89. Hikaru Komatsu, Tomonori Kume, Yoshinori Shinohara, Yoshiyuki Miyazawa, Kyoichi Otsuki, Did annual run-off and low flow decrease with reduced forestry practices in Japan?, Hydrological Processes, 10.1002/hyp.7657, 24, 17, 2440-2451, 2010.08, Japan developed large areas of coniferous plantations for timber production between the 1950s and 1970s; however, forestry practices such as thinning, pruning, and harvesting in most of the plantations have declined since the 1980s. Researchers speculated that reduced forestry practices could reduce run-off and therefore available water resources. As a countermeasure to this potential risk, many local governments have introduced local taxes to stimulate forestry practices in the plantations. However, no studies have presented evidence for decreased annual run-off and/or low flow in watersheds where forestry practices have declined. As a starting point for assessing this risk, this study examined potential changes in the annual run-off and low flow in the Terauchi watershed. A large area of this watershed was covered with coniferous plantations. We first surveyed the annual investment in forestry operations and the number of forest owners in the city of Amagi. (Note that Amagi includes the Terauchi watershed.) Both decreased during the period 1979-2007, indicating reduced forestry practices. The frequency distribution of plantation tree ages in the watershed also suggested reduced forestry practices. After excluding the effect of precipitation, we examined potential changes in the annual run-off and low flow during the period 1979-2007. We did not observe significant decreases in the annual run-off and low flow during the period. Thus, the risk of decreased water resources might be less than expected, and countermeasures to the risk should be reconsidered..
90. Shinohara, Y., Kume, T., Komatsu, H. and Otsuki, K., Spatial and temporal variations in summer precipitation in Japanese mountain areas, Hydrological Processes, 10.1002/hyp.7620, 24, 1844-1855, 2010.06.
91. Komatsu, H., Kume, T. and Otsuki, K., A simple model to estimate monthly forest evapotranspiration in Japan from monthly temperature, Hydrological Processes, 10.1002/hyp.7622, 24, 1844–1855, 2010.06.
92. Hikaru Komatsu, Hirofumi Hashimoto, Tomonori Kume, Nobuaki Tanaka, Natsuko Yoshifuji, Kyoichi Otsuki, Masakazu Suzuki, Tomo'omi Kumagai, Modeling seasonal changes in the temperature lapse rate in a Northern Thailand mountainous area, Journal of Applied Meteorology and Climatology, 10.1175/2010JAMC2297.1, 49, 6, 1233-1246, 2010.06, Temperature data in the mountain forest regions are often extrapolated from temperature data recorded at base stations at lower elevation. Such extrapolation is often based on elevation differences between target regions and base stations at low elevation assuming a constant temperature lapse rate throughout the year. However, this assumption might be problematic where slope circulation is active and decoupled from the regional circulation. To model the seasonal change in the lapse rate, the authors compared daily maximum (Tmax) and minimum temperatures (Tmin) observed at a mountain forest site (Kog-Ma; 1300-m altitude) with those observed at the bottom of the basin (Chiang-Mai; 314-m altitude) in northern Thailand, where slope circulation is active and decoupled from the regional circulation. The difference in Tmax between Kog-Ma and Chiang-Mai (ΔTmax; Kog-Ma minus Chiang-Mai) was relatively unchanged throughout the year. However, the difference in Tmin between Kog-Ma and Chiang-Mai (ΔTmin) changed seasonally. Thus, assuming a constant lapse rate throughout the year could cause large errors in extrapolating Tmin data in mountainous areas in northern Thailand. The difference ΔTmin was related to nighttime net radiation (Rn), suggesting that nocturnal drainage flow affects the determination of ΔTmin. This relationship would be useful in formulating seasonal changes in the lapse rate for Tmin. As Rn data are generally unavailable for meteorological stations, an index that relates to the lapse rate for Tmin and is calculated from Tmax and Tmin data is proposed. This index might be useful for accurately estimating Tmin values in mountainous regions in northern Thailand..
93. Toshihiro Umebayashi, Yasuhiro Utsumi, Shinya Koga, Susumu Inoue, Junji Matsumura, Kazuyuki Oda, Seizo Fujikawa, Keita Arakawa, Kyoichi Otsuki, Xylem water-conducting patterns of 34 broadleaved evergreen trees in southern Japan, Trees - Structure and Function, 10.1007/s00468-010-0428-7, 24, 3, 571-583, 2010.06, A dye injection method was used to elucidate the xylem water-conducting pathways of 34 broadleaved evergreen trees growing in southern Japan: two semi-ring-porous, 26 diffuse-porous, five radial-porous and one non-vessel species. The large earlywood vessels in semi-ring-porous species have a water transport function in only the outermost annual ring, as in deciduous ring-porous species. On the other hand, the small vessels in semi-ring-porous species maintain the water transport function in many outer annual rings. For the other xylem-type species, the many vessels in many outer annual rings have a water transport function. In diffuse-porous species, we categorized the water-conducting pattern within the annual rings into two types: d1 type, where water travels through vessels in the whole region; and d2 type, where water travels mainly through the earlywood vessels. The pattern in radial-porous species is similar to that in the d1 type; the pattern in non-vessels species is similar to that in the d2 type. The vessel diameter in radial-porous species is similar to that of the earlywood vessels of semi-ring-porous species. These results suggest that the conduit diameter size is only one of many factors determining the water-conducting pathways of broadleaved evergreen species..
94. Yoshinori Shinohara, Junichiro Ide, Naoko Higashi, Hikaru Komatsu, Tomonori Kume, Masaaki Chiwa, Kyoichi Otsuki, Observation of canopy interception loss in an abandoned coniferous plantation, Nihon Ringakkai Shi/Journal of the Japanese Forestry Society, 92, 1, 54-59, 2010.04, The number of abandoned coniferous plantations has increased greatly in recent year across Japan. However, though evapotranspiration greatly affects on available water resources, no study observing evapotranspiration in abandoned plantations has been reported. We observed canopy interception loss for four years in an abandoned coniferous plantation located in the Kasuya Research Forest of Kyushu University. Our results were compared with those obtained for other coniferous forests. The canopy interception loss ratio (interception loss/precipitation) we obtained was 24.9%. The relationship between stem density and interception ratio has previously reported. Indeed, the value we obtained was nearly that calculated based on that reported relationship; this information would be useful for examining whether the relationship derived from previous interception studies in coniferous plantations holds even for abandoned coniferous plantations..
95. Masaaki Chiwa, Ryoko Maruno, Jun'Ichiro Ide, Takeaki Miyano, Naoko Higashi, Kyoichi Otsuki, Role of stormflow in reducing N retention in a suburban forested watershed, western Japan, Journal of Geophysical Research: Biogeosciences, 10.1029/2009JG000944, 115, 2, 2010.04, To evaluate the role of stormflow in reducing N retention in forested watersheds, we investigated the inorganic N budget of a Japanese suburban forested watershed for 4 years where the proportion of direct flow to precipitation is considerably high (mean is 33%; range is 25-42%). Soil net N mineralization and net nitrification were also measured at middle and lower positions of a slope within the watershed to evaluate nitrate (NO 3-) pool size. Annual mean N deposition via throughfall plus stemflow was 15.5 kg N ha-1 yr-1 (13.6-17.1 kg N ha-1 yr-1), which exceeded the threshold value to potentially induce N leaching from forested watersheds. Net nitrification at the middle position was comparable with the lower position. This suggests that the NO3- rich area is large, which could be partly caused by comparable soil moisture conditions with the lower position due to rising groundwater levels during storm events. Annual mean N export was 10.4 kg N ha-1 yr-1 (7.8-12.5 kg N ha-1 yr-1), and subsequent N retention was distinctly low 33% (12-53%). Stormflow accounted for more than 80% of total annual N export. Furthermore, N retention was lower (12 and 27%) in years with higher proportions of direct flow than in years with lower proportions (36 and 53%). Therefore, stormflow is a significant factor in reducing N retention in forested watersheds. The effect of stormflow observation on the comparison of N budgets in other watersheds with different climate and/or hydrologic conditions is discussed..
96. Yoshiyuki Miyazawa, Kyoichi Otsuki, Comparison of sapling-level daily light capture and carbon gain between a temperate deciduous and a co-occurring evergreen tree species in the growing season and in winter, Functional Plant Biology, 10.1071/FP09168, 37, 3, 215-222, 2010.03, Light capture efficiency (Ea) and mass-based daily carbon gain (Amass) were compared between saplings of a deciduous tree species, Ficus erecta Thunb. and the co-occurring evergreen broadleaved tree species, Neolitsea aciculata (Bl.) Koidzumi, in a temperate forest in Japan. Using obtained data and an ecophysiologicalarchitectural model, we calculated the Ea and Amass of each study sapling. We also analysed the response of Amass to changes in photosynthetic traits and E a. Saplings of F. erecta had a higher Amass than N. aciculata, due to the high leaf area:aboveground mass ratio (LAR). The model calculation suggested that changes in photosynthetic traits and Ea changed Amass but did not modify the interspecific difference of Amass. In winter Amass was lower than that in the growing season due to low light availability during the short day lenght, suggesting modest importance of winter carbon gain for the evergreen saplings of N. aciculata. In conclusion, the advantage of this deciduous species for carbon gain over the co-occurring evergreen broadleaved saplings is not modified by acclimative changes in leaf physiology, crown architecture or prolonged photosynthesis period by evergreen broadleaved trees..
97. Hikaru Komatsu, Tomonori Kume, Kyoichi Otsuki, Water resource management in Japan
Forest management or dam reservoirs?, Journal of Environmental Management, 10.1016/j.jenvman.2009.10.011, 91, 4, 814-823, 2010.03, Researchers and journalists in Japan recently proposed forest management as an alternative to dam reservoir development for water resource management. To examine the validity of the proposal, we compared the potential low-flow increase due to forest clearcutting with the increase due to dam reservoir development. Here, we focused on forest clearcutting as an end member among various types of forest management. We first analyzed runoff data for five catchments and found a positive correlation between annual precipitation and the low-flow increase due to deforestation. We then examined the increase in low-flow rates due to dam reservoir development (dQd) using inflow and outflow data for 45 dam reservoirs across Japan. Using the relationship between annual precipitation and the low-flow increase due to deforestation, we estimated the potential increase in the low-flow rate for each dam reservoir watershed if forests in the watershed were clearcut (dQf). Only 6 of the 45 samples satisfied dQf > dQd, indicating that the potential increase in the low-flow rate due to forest clearcutting was less than the increase due to dam reservoir development in most cases. Twenty-five of the 45 samples satisfied dQf < 0.2 dQd, indicating the potential increase in the low-flow rate due to forest clearcutting was less than 20% of the increase due to dam reservoir development in more than half the cases. Therefore, forest management is far less effective for water resource management than dam reservoir development is in Japan..
98. Guoqiang Wang, Baolin Xue, Jingshan Yu, Kyoichi Otsuki, A GIS-based linear programming model for optimizing agricultural land levelling, Journal of the Faculty of Agriculture, Kyushu University, 55, 1, 131-135, 2010.02, Land levelling is an important process of the agricultural land consolidation projects. The land levelling process starts by determining the appropriate levels of the terrain and solves the earthwork allocation for the predetermined terrain levels. The recent attempt, reported in the literature, to find an optimal process is a GIS-based approach which solves the transportation problem by determing the designed terrain level and optimal hauling distances that result in the lowest hauling cost. In this study, the Vogel approximation method (VAM) was adopted in initializing the solution to the transportation problems, and the optimization of the solutions obtained by the VAM was examined using the modified distribution method (MODI). To verify the reliability of this combined method, a case study was carried out based on the proposed land levelling project at the Lixian District of Beijing, China. The results show that the optimal average hauling distance calculated from the proposed linear programming model is 79.53m shorter than that estimated using the empirical method, and the unit cost calculated from the linear programming model is 33.4% lower than the experienced cost. The improvements in the optimization of the hauling distance show that the cost of the agricultural land levelling can be efficiently lowered if an appropriate linear programming model is used..
99. Masaaki Chiwa, Junichiro Ide, Ryoko Maruno, Naoko Higashi, Kyoichi Otsuki, Effects of storm flow samplings on the evaluation of inorganic nitrogen and sulfate budgets in a small forested watershed, Hydrological Processes, 10.1002/hyp.7557, 24, 5, 631-640, 2010.02, To investigate the effects of storm flow samplings on the evaluation of DIN and SO4 2- budgets, we conducted storm flow samplings and discrete interval (weekly) samplings of stream water, throughfall, and stemflow. This investigation lasted for three years and took place in a small forested watershed in western Japan. Annual exports were calculated by the sum of the load (∑Ltotal)sum of the discharge (∑Qtotal) relationships obtained by storm flow samplings. These were then compared to calculated ones that were based on LQ relationships obtained by discrete interval sampling. The results of discrete interval sampling showed that the relationships of DIN or SO4 2- concentration to the discharge amount found in stream water differed from those of storm flow sampling. This was especially notable in years with higher annual precipitation and subsequent higher annual discharges. Also, exports of DIN and SO4 2during storm flow periods accounted for 83% and 78% of annual exports on 3-year averages, respectively. These results confirmed that storm flow samplings are essential for estimating annual exports of DIN and SO4 2-. Annual exports that were calculated based on just discrete interval sampling (46% and 17%, respectively) overestimated DIN and SO4 2- from discrete interval and storm flow samplings on a 3-year average. These overestimates were pronounced in years of higher discharge, and critically affected the rates of net-retention or export of DIN and SO4 2-. The relationship of smaller input than output of DIN was reversed if storm flow sampling was included..
100. Kume, T., Tsuruta, K., Komatsu, H., Kumagai, T., Higashi, N., Shinohara, Y. and Otsuki, K., Sample sizes for sap flux-based stand-scale transpiration estimates in a Japanese cypress forest, Tree Physiology, 30, 129-138, 2010.01.
101. Du, S., Wang, Y., Kume, T., Zhang, J., Otsuki, K., Yamanaka, N. and Liu, G., Sapflow characteristics and climatic responses in three forest species in the semiarid Loess Plateau region of China, Agricultural and Forest Meteorology, 10.1016/j.agrformet.2010.08.011, 151, 1-10, 2010.01, [URL].
102. Tomonori Kume, Kenji Tsuruta, Hikaru Komatsu, Tomo'omi Kumagai, Naoko Higashi, Yoshinori Shinohara, Kyoichi Otsuki, Effects of sample size on sap flux-based stand-scale transpiration estimates, Tree physiology, 10.1093/treephys/tpp074, 30, 1, 129-138, 2010.01, In this study, we aimed to assess how sample sizes affect confidence of stand-scale transpiration (E) estimates calculated from sap flux (Fd) and sapwood area (AStree) measurements of individual trees. In a Japanese cypress plantation, we measured Fd and AS-tree in all trees (n = 58) within a 20 × 20 m study plot, which was divided into four 10 × 10 subplots. We calculated E from stand AS-tree (A S-stand) and mean stand Fd (JS) values. Using Monte Carlo analyses, we examined the potential errors associated with sample sizes in E, AS-stand and JS using the original AS-tree and F d data sets. Consequently, we defined the optimal sample sizes of 10 and 15 for AS-stand and JS estimates, respectively, in the 20 × 20 m plot. Sample sizes larger than the optimal sample sizes did not decrease potential errors. The optimal sample sizes for JS changed according to plot size (e.g., 10 × 10 and 10 × 20 m), whereas the optimal sample sizes for AS-stand did not. As well, the optimal sample sizes for JS did not change in different vapor pressure deficit conditions. In terms of E estimates, these results suggest that the tree-to-tree variations in Fd vary among different plots, and that plot size to capture tree-to-tree variations in Fd is an important factor. The sample sizes determined in this study will be helpful for planning the balanced sampling designs to extrapolate stand-scale estimates to catchmentscale estimates..
103. Yoshinori Shinohara, Yuka Onozawa, Masaaki Chiwa, Tomonori Kume, Hikaru Komatsu, Kyoichi Otsuki, Spatial variations in throughfall in a Moso bamboo forest
Sampling design for the estimates of stand-scale throughfall, Hydrological Processes, 10.1002/hyp.7473, 24, 3, 253-259, 2010.01, We investigated the spatial and seasonal variations in throughfall (Tf) in relation to spatial and seasonal variations in canopy structure and gross rainfall (Rf) and assessed the impacts of the variations in Tf on stand-scale Tf estimates. We observed the canopy structure expressed as the leaf area index (LAI) once a month and Tf once a week in 25 grids placed in a Moso bamboo (Phyllostachys pubescens) forest for 1 year. The mean LAI and spatial variation in LAI did have some seasonal variations. The spatial variations in Tf reduced with increasing Rf, and the relationship between the spatial variation and the Rf held throughout the year. These results indicate that the seasonal change in LAI had little impact on spatial variations in Tf, and that Rf is a critical factor determining the spatial variations in Tf at the study site. We evaluated potential errors in stand-scale Tf estimates on the basis of measured Tf data using Monte Carlo sampling. The results showed that the error decreases greatly with increasing sample size when the sample size was less than ~8, whereas it was near stable when the sample size was 8 or more, regardless of Rf. A sample size of eight results in less than 10% error for Tf estimates based on Student's t-value analysis and would be satisfactory for interception loss estimates when considering errors included in Rf data..
104. Yuka Onozawa, Tomonorl Koine, Hikaru Komatsu, Kenji Tsuruta, Kyoichi Otsuki, Applicability of sap flux measurements in moso bamboo (phyłł ostachys pubescens)
Relationship between water absorption and wholetree water use utilizing granler sensor sap flux measurements, Nihon Ringakkai Shi/Journal of the Japanese Forestry Society, 91, 5, 366-370, 2009.12, Although sap flux measurement is one of the most robust techniques for stand-scale transpiration estimates, its applicability to bamboo is unclear. Ultimately we aim to establish a method for sap flux-based stand-scale transpiration estimates in a bamboo forest This study focused on establishing a method for individual-scale transpiration estimates. We conducted sap flux measurements using hand-made 1-cm length sensors, and water absorption measurements in cut-bamboo. The sensors could detect water uptake in individual plants (i.e., sap flux in moso bamboo). The diurnal changes in sap flux density reasonably well corresponded to those in water absorption. We found there was an underestimation of whole-tree water use with the 1-cm Grainer sensor; thus we suggested a modified equation for the calculation of sap flux density. In this study we could estimate individual-scale transpiration in moso bamboo using sap flux measurements..
105. Ayumi Katayama, Tomonori Kume, Hikaru Komatsu, Mizue Ohashi, Michiko Nakagawa, Megumi Yamashita, Kyoichi Otsuki, Masakazu Suzuki, Tomo'omi Kumagai, Effect of forest structure on the spatial variation in soil respiration in a Bornean tropical rainforest, Agricultural and Forest Meteorology, 10.1016/j.agrformet.2009.05.007, 149, 10, 1666-1673, 2009.10, This study was undertaken to identify critical and practical factors explaining spatial variations in soil respiration and to estimate stand-scale soil respiration in an aseasonal tropical rainforest on Borneo Island. To this aim, we conducted soil respiration measurements at 25 points in a 40 m × 40 m subplot of a 4 ha study plot between 2002 and 2006, and examined the spatial variation in soil respiration averaged over the 4 years in relation to soil, root, and forest structural factors. In addition, we examined the spatial representativeness of soil respiration measured in the subplot using a specific scaling procedure. Consequently, we found significant positive correlation between the soil respiration and forest structural parameters such as the mean diameter at breast height (DBH), total basal area, and maximum DBH within 6 m of the measurement points. The most important factor was the mean DBH within 6 m of the measurement points, which had a significant linear relationship with soil respiration. Using the derived linear regression and an inventory dataset, we estimated the 4 ha plot-scale soil respiration. The 4 ha plot-scale estimation (6.0 μmol m-2 s-1) was nearly identical to the subplot-scale measurements (5.7 μmol m-2 s-1), which were roughly comparable to the nocturnal CO2 fluxes calculated using the eddy covariance technique. In addition, we discuss characteristics of the stand-scale soil respiration at this site by comparing with those of other forests reported in previous literature in terms of the soil C balance. Soil respiration at our site was noticeably greater, relative to the incident litterfall amount, than soil respiration in other tropical and temperate forests probably owing to the larger total belowground C allocation by emergent trees. Overall, this study suggests the arrangement of emergent trees with larger DBH and their belowground C allocation could be primary factors controlling spatial variations in soil respiration in the tropical rainforest..
106. Hikaru Komatsu, Tomonori Kume, Kyoichi Otsuki, Effects of coniferous plantation thinning on annual interception evaporation
Model verification, Nihon Ringakkai Shi/Journal of the Japanese Forestry Society, 91, 2, 94-103, 2009.09, For evaluating the effect of coniferous plantation thinning on water resources, our previous study (Komatsu et al., 2007c) developed a model for predicting changes in annual evapotranspiration caused by coniferous plantation thinning. This model is comprised of transpiration and interception evaporation parts. The model needs to be verified from three viewpoints, stability of transpiration amounts with thinning, decrease in interception evaporation amounts with thinning, and applicability of the model to catchment scale. This study mainly focused on verification of the interception evaporation part. Based on seven datasets of interception evaporation derived from earlier publications, we compared model prediction results with the observed results. Model prediction results agreed fairly well with the observed results, indicating validity of the interception evaporation part of the model. Based on one dataset for verifying applicability of the model to catchment scale, model prediction results agreed fairly well with the observed results, implying applicability of the model to catchment scale. We should note that validity of the transpiration part of the model was not examined. Applicability of the model to catchment scale was not fully examined due to lack of observation data. Thus, we raised observation data that should be required for further model verification and presented guidelines for future observation studies..
107. Tomo'omi Kumagai, Sayaka Aoki, Kyoichi Otsuki, Yasuhiro Utsumi, Impact of stem water storage on diurnal estimates of whole-tree transpiration and canopy conductance from sap flow measurements in Japanese cedar and Japanese cypress trees, Hydrological Processes, 10.1002/hyp.7338, 23, 16, 2335-2344, 2009.07, The amount of water stored in the stem introduces uncertainty when estimating diurnal whole-tree transpiration (ET) and canopy stomatal conductance (GC) using sap flow measured at the base of the stem (Q). Thus, to examine how ET can be calculated from Q, we obtained ET using sap flow and stem water content measurements and a whole-tree water balance equation, and compared it with Q. In this study, we measured sap flows in 33-year-old individual trees of Cryptomeria japonica D. Don and Chamaecyparis obtusa Endl. using constant-heat sap flow probes. Sap flows were measured at several depths at the base of the stem, and at the upper trunk as a surrogate of ET. Stem water contents were measured at three vertical positions on the trunk using amplitude-domain reflectometry (ADR) sensors. We also measured sapwood volumes of the study trees. Using simultaneous sap flow and stem water content measurements along the tree stem, we confirmed that stem water storage has impacts on the transpiration stream. These include sap flow lags along the tree heights and an enhanced peak of transpiration from stem sap flow. These results enabled us to calculate the correct ET by multiplying Q by 1.18 and shifting its time series forward by 30 min. The ET value was then used to calculate GC for both tree species. The factor of 1.18 is based on the fact that at noon, the value of ET was higher than that of Q, due to the prolonged Q during the evening. Establishing the time lag was relatively simple and was determined by comparing Q and vapor pressure deficit. The multiplier is more challenging to ascertain due to the difficulty in obtaining ET correctly..
108. Hikaru Komatsu, Tomonori Kume, Kyoichi Otsuki, Changes in low flow with the conversion of a coniferous plantation to a broad-leaved forest in a summer precipitation region, Japan, Ecohydrology, 10.1002/eco.50, 2, 2, 164-172, 2009.06, Converting coniferous plantations to broad-leaved forests is believed to result in increased runoff in Japan. This study examined low-flow changes in runoff in the Tatsunokuchi-Minami catchment, located in a region with summer precipitation, caused by the conversion of a coniferous plantation to a broad-leaved forest. We compared the flow duration curves for the coniferous plantation period with those for the broad-leaved forest period. We observed no evidence of increased low flows according to the change in forest type. Thus, the commonly held belief was not supported by the results from a summer precipitation region with respect to low-flow rates..
109. Yoshinori Shinohara, Tomo'omi Kumagai, Kyoichi Otsuki, Atsushi Kume, Naoya Wada, Impact of climate change on runoff from a mid-latitude mountainous catchment in central Japan, Hydrological Processes, 10.1002/hyp.7264, 23, 10, 1418-1429, 2009.05, Hydrologic balance in high-altitude, mid-latitude mountain areas is important in terms of the water resources available to associated lowlands. This study examined how current and historical shifts in precipitation (P) patterns and concurrent increases in temperature (T) affected runoff (Q) and other hydrologic components in a mid-latitude mountain catchment of central Japan, using a combination of long-term data and a simplified hydrologic model, along with their stochastic treatment. The availability of intensive meteorological and hydrological data from the period 1997-2001 allowed the derivation of key relationships for the current climate that tie the forcing term to the parameters or state variables. By using the data recorded in the period 1965-2001, the force for driving the historical simulation was generated. Based on this model and historical shifts in P and T, the probability density functions of Q (pdf(Q)) was computed. A main novelty in this study is that such a stochastic representation, which is useful for considering the influence of projected shifts in environmental factors on the hydrologic budget, was provided. Despite the large increase in the rate of T in winter and spring, pdf(Q) in spring and summer varied appreciably during the time studied mainly because of an increase in snowmelt. An interannual change in whole-year Q was robust to shifts in T because while Q in spring increased, in summer it decreased, implying a crucial effect of global warming on mountain hydrologic regimes is change in the timing of Q..
110. Jun'ichiro Ide, Tomonori Kume, Yoshifumi Wakiyama, Naoko Higashi, Masaaki Chiwa, Kyoichi Otsuki, Estimation of annual suspended sediment yield from a Japanese cypress (Chamaecyparis obtusa) plantation considering antecedent rainfalls, Forest Ecology and Management, 10.1016/j.foreco.2009.02.011, 257, 9, 1955-1965, 2009.04, Japanese cypress (Chamaecyparis obtusa) is one of the most common plantation species in Japan. In most Japanese cypress plantations, closure of the forest canopy hinders understory growth because of insufficient management practices. Thus leaf litter barely covers the soil surface. Such plantations are vulnerable to surface erosion triggered by rainfalls, and could yield large amounts of suspended sediment (SS). However, few studies have investigated the annual SS yield. This study aimed to develop a modified model of SS yields, and to accurately estimate and characterize the annual SS yield from a Japanese cypress plantation. For this, hydrological surveys were conducted for 5 years, and stream water was sampled weekly as well as sequentially at 15-60 min intervals in each of 14 rain events in a small forested watershed of Japanese cypress. The root mean square error (RMSE) and the annual SS yield estimates were obtained using three different equations: the rating curve derived from instantaneous SS concentration versus stream discharge relationship (SSC - Q equation); the rating curve derived from cumulative SS yield versus cumulative specific discharge relationship (∑SS - ∑Q equation); and the multiple regression of cumulative SS yield expressed as functions of cumulative specific discharge and antecedent rainfalls (∑SS - ∑Q × AR equation). The ∑SS - ∑Q × AR equation is a modified model considering the effects of antecedent rain history on the SS yield. The parameters in each equation were determined by a nonlinear least square method. Of the three equations, the RMSE was the highest using the SSC - Q equation. Although the ∑SS - ∑Q equation and the ∑SS - ∑Q × AR equation gave similar RMSE values, the SS yields extrapolated by the ∑SS - ∑Q equation would be overestimated. Thus, the 5-year average of annual SS yield estimated by the ∑SS - ∑Q equation was three times larger than that estimated by the ∑SS - ∑Q × AR equation. These results indicate that the ∑SS - ∑Q × AR equation more accurately estimates the annual SS yield, compared with the other two equations. The results also suggest that antecedent rain history, as well as stream discharge, should be considered for appropriately estimating the annual SS yield. The annual SS yield estimated by the ∑SS - ∑Q × AR equation was the largest among 25 undisturbed forested watersheds, except for two watersheds dominated by sandstone. Our results suggest that the annual SS yield is greater from a Japanese cypress plantation under current management practices than from other undisturbed forests..
111. Yuka Onozawa, Masaaki Chiwa, Hikaru Komatsu, Kyoichi Otsuki, Rainfall interception in a moso bamboo (Phyllostachys pubescens) forest, Journal of Forest Research, 10.1007/s10310-008-0108-2, 14, 2, 111-116, 2009.04, In recent years, moso bamboo (Phyllostachys pubescens) forest areas in Japan have rapidly expanded, and bamboo is now invading nearby natural or plantation forests. To date, only one study has examined the rainfall interception of a moso bamboo forest. In that study, it was reported that the interception ratio (interception/rainfall) of the bamboo forest did not exceed the interception ratios of other natural and plantation forests (n = 4) in Japan. To expand the current state of knowledge about rainfall interception of bamboo forests, we measured throughfall and stemflow at another bamboo forest site. Annual rainfall (Rf), throughfall (Tf), and stemflow (Sf) during the measurement period were 2,105, 1,556, and 322 mm, respectively. Annual rainfall interception at the plot (I) was 228 mm. Tf/Rf, Sf/Rf, and I/Rf were 73.9, 15.3, 10.8%, respectively. I/Rf was less than 20% throughout the year except in October, the month with lowest rainfall. We also summarized rainfall interception data from 19 other natural and plantation forests. The I/Rf value of our site did not exceed the I/Rf values of these natural and plantation forests (n = 19). Our data will be useful for assessing changes in water resources that result from replacement of natural or plantation forests by bamboo forests..
112. Dawen Yang, Kyoichi Otsuki, Tetsuo Kobayashi, Daisuke Yasutake, Hiroyuki Cho, Masaharu Kitano, Makito Mori, Tugihiro Watanabe, Kuniyoshi Takeuchi, Hiroshi Ishidaira, Changrong Yan, Water resources and use, The Yellow River Water and Life, 10.1142/9789814280969_0003, 25-72, 2009.01.
113. Tomo'omi Kumagai, Makiko Tateishi, Takanori Shimizu, Kyoichi Otsuki, Transpiration and canopy conductance at two slope positions in a Japanese cedar forest watershed, Agricultural and Forest Meteorology, 10.1016/j.agrformet.2008.04.010, 148, 10, 1444-1455, 2008.09, Plant-soil system patterns and processes along a slope are among the greatest causes of uncertainty in estimating watershed-scale transpiration (E). Tree-to-tree and radial variations in xylem sap flux density (Fd), in addition to tree biometrics, were measured over a 2-year period (2005-2006) in two slope stand positions. The areas of interest consisted of an upper slope plot (UP) and a lower slope plot (LP) in a Japanese cedar (Cryptomeria japonica D. Don) forest watershed and the environmental controls of stand E for each plot were compared. Canopy stand E (EC) and canopy stomatal conductance (GC) in the UP were less than those in the LP during the growing season, while those in the UP were greater than those in the LP over winter. In addition, mean stand Fd (JS) in the UP was greater than that in the LP over winter, but JS values were similar in the UP and LP except in the winter, which allows us to extrapolate watershed-scale E based on JS estimated from Fd measurements of a partial stand in the watershed. However, this relationship contains a bias and differed between 2005 and 2006. Although there were significant differences in soil moisture conditions between the UP and LP in both years, a systematic relationship between the similarity in JS and soil moisture conditions was not found. The bias was due to a tendency for JS in the LP to be greater than that in the UP in 2006. This tendency was amplified because JS in the LP was greater than that in the UP around an atmospheric humidity deficit (D) of 1-1.5 kPa and frequencies of this D range were higher in 2006 than in 2005. The greater JS in the LP at D ∼ 1-1.5 kPa could be explained by the difference in the response of GC to D between the UP and LP. Our results suggest this to be the cause of the similarity in JS values for the UP and LP and for the occasional abortion of its similarity. However, even when the bias or the occasional deviation is disregarded, the error in estimating stand E from a partial stand is so small that it is comparable to an Fd measurement error. For example, the error when using only the LP was 6.6% for stand E..
114. Komatsu, H., Shinohara, Y.,Kume, T. and Otsuki, K., Relationship between annual rainfall and interception ratio for forests across Japan, Forest Ecology and Management, 256, 1189-1197, 2008.08.
115. Hikaru Komatsu, Yoshinori Shinohara, Tomonori Kume, Kyoichi Otsuki, Relationship between annual rainfall and interception ratio for forests across Japan, Forest Ecology and Management, 10.1016/j.foreco.2008.06.036, 256, 5, 1189-1197, 2008.08, Several previous studies in Japan have examined differences in rainfall interception amounts induced by differences in forest properties by comparing the annual rainfall interception ratios (annual rainfall interception divided by annual rainfall) from various sites without considering variations in meteorological conditions between sites. Rainfall interception actually depends on meteorological conditions as well as forest properties. This study examined variations in the annual interception ratio relating to the variation in annual rainfall, which would be the primary factor relating to the interception ratio, across Japan with the use of a rainfall interception model assuming the same forest properties (i.e., the canopy storage capacity, canopy closure, leaf area index (LAI), and the bulk coefficient for sensible heat transfer). The ratio ranged between 0.12 and 0.24 across Japan and was highly correlated to annual rainfall. This indicates that considering the variation in annual rainfall is critical for assessing the difference in rainfall interception amounts induced by forest properties. We reconsidered the results of previous studies in Japan that compared annual interception ratios between sites with different forest properties: (i) there is no clear difference in interception amounts between broadleaf and coniferous forests and (ii) there is a positive correlation in stem density and interception amounts for coniferous forests. These results still held when considering differences in annual rainfall between sites..
116. Junichiro Ide, Hirokazu Haga, Masaaki Chiwa, Kyoichi Otsuki, Effects of antecedent rain history on particulate phosphorus loss from a small forested watershed of Japanese cypress (Chamaecyparis obtusa), Journal of Hydrology, 10.1016/j.jhydrol.2008.01.012, 352, 3-4, 322-335, 2008.05, This study aimed to clarify the effects of antecedent rain history on particulate phosphorus (PP) loss in a small mountainous watershed covered primarily with a plantation forest of Japanese cypress (Chamaecyparis obtusa). We analyzed stream discharge and PP concentration at 15-60 min intervals during 24 h in eight rain events with different discharge levels. The PP concentration versus stream discharge (PPC-Q) relationships exhibited clockwise hysteresis loops for each of the eight events monitored. Discharge could explain changes in PP concentration on the falling but not rising limb of the hydrograph. On the rising limb, a positive relationship between the rate of changes in discharge (dQ/dt) and the PP load (dL/dt) was found for each event. This indicates that a large amount of PP is strongly pulsed at times of rapidly increased discharge. These results suggest that dQ/dt is the driving force behind PP supply and the primary control on the clockwise hysteresis loop of PPC-Q relationship. There was a strong negative correlation between the antecedent precipitation index and the slope of the dL/dt versus dQ/dt relationship. This shows that a rapid increase in PP load occurs even with slight increases in discharge as antecedent moisture conditions become drier. The soil water repellency and rapid runoff response following dry conditions support that soil desiccation increases the PP supply associated with soil erosion via overland flow. Therefore, we concluded that the antecedent rain history affects the mobility of PP via soil desiccation. The findings of this study will fill gaps in our understanding of temporal variations in released fine sediment and associated PP as reported in previous studies..
117. Hikaru Komatsu, Tomonori Kume, Kyoichi Otsuki, The effect of converting a native broad-leaved forest to a coniferous plantation forest on annual water yield
A paired-catchment study in northern Japan, Forest Ecology and Management, 10.1016/j.foreco.2007.10.010, 255, 3-4, 880-886, 2008.03, This study examined the change of water yield when a broad-leaved forest is converted to a coniferous plantation forest after clear-cutting in northern Japan where monthly precipitation is evenly distributed. Annual water yield after clear-cut was greater than observed in a broad-leaved forest and then decreased with the growth of a coniferous plantation forest. This reduction ceased after 30 years from the planting of coniferous seedlings. Water yield of a coniferous forest at this stage was smaller than observed in a broad-leaved forest. Results from monthly water yield examinations suggested that the difference in annual water yield was primarily caused by the difference in winter interception loss between broad-leaved deciduous and coniferous evergreen forests. The above results suggest that converting coniferous forests into broad-leaved forests can be used to increase water yield in these regions..
118. Yoshiyuki Miyazawa, Kihachiro Kikuzawa, Kyoichi Otsuki, Evaluation of leaf display of evergreen broadleaved tree species and deciduous tree species in warm temperate conifer plantations, Journal of Forest Research, 10.1007/s10310-007-0049-1, 13, 1, 59-67, 2008.02, We investigated the sapling leaf display in the shade among trees of various leaf lifespans co-occurring under the canopy of a warm-temperate conifer plantation. We measured leaf-area ratio (aLAR) and morphological traits of saplings of evergreen broadleaved tree species and a deciduous tree species. Although we found large interspecific and intraspecific differences in aLAR even among saplings of similar size in the homogeneous light environment, we did not find a consistent trend in aLAR with leaf lifespan among the species. While deciduous trees annually produced a large leaf area, some evergreen broadleaved trees retained their leaves across years and had aLAR values as high as those of deciduous trees. Among leaf-level, shoot-level, and individual-level morphological traits, aLAR was positively correlated with current-year shoots mass per aboveground biomass in deciduous trees, and with the area of old leaves per aboveground mass in evergreen broadleaved trees. Thus, tree-to-tree variation in the degrees of annual shoot production and the accumulation of old leaves were responsible for the interspecific and intraspecific variations in aLAR..
119. Makiko Tateishi, Tomo'omi Kumagai, Yasuhiro Utsumi, Toshihiro Umebayashi, Yasuki Shiiba, Kazunobu Inoue, Kiyohiro Kaji, Keiichiro Cho, Kyoichi Otsuki, Spatial variations in xylem sap flux density in evergreen oak trees with radial-porous wood
Comparisons with anatomical observations, Trees - Structure and Function, 10.1007/s00468-007-0165-8, 22, 1, 23-30, 2008.02, To estimate whole-tree water use when employing sap flow measurements, integration of the sap flux density (Fd) over the sapwood area is needed. Accordingly, it is necessary to obtain information on the characteristics of stem water transportation such as spatial variations in Fd and the active xylem area in the stem cross-section. Although evergreen oak trees with radial-porous wood represent a major component of secondary forests in western Japan, detailed information on their stem water transportation characteristics remains unclear. In the present study, we used the heat dissipation method (Granier method) to conduct measurements of azimuthal and radial variations in the Fd of Quercus glauca Thunb. ex Murray, a representative evergreen broad-leaved tree in western Japan. Further, by analyzing the anatomy of the xylem structure, we examined why Fd varies spatially in the stem cross-section. By using a dye solution injected into a radial hole bored into the tree trunk, we confirmed that the entire stem is hydroactive. We also compared the spatial variations in Fd and water conductivity per xylem area (Ks) which were estimated by using the observed vessel diameters and their density over the stem cross-section and Hagen-Poiseuille's law. Azimuthal and radial variations in Fd reached about 60 and 50% of the maximum values, respectively, and could be explained by spatial variation in Ks. As a result, we obtained statistical parameters describing the spatial variation in Fd in Q. glauca and determined that whole-tree water use estimated from measurements in one direction had at most ±20% potential errors for studied trees..
120. Komatsu, H.,, Maita, E. and Otsuki, K., A model to estimate annual forest evapotranspiration in Japan from mean annual temperature, Journal of Hydrology, 348, 330-340, 2008.01.
121. Hikaru Komatsu, Eiichi Maita, Kyoichi Otsuki, A model to estimate annual forest evapotranspiration in Japan from mean annual temperature, Journal of Hydrology, 10.1016/j.jhydrol.2007.10.006, 348, 3-4, 330-340, 2008.01, In Japan, forested areas are usually located upstream of urban and agricultural areas. Estimating annual water yield from such forested areas is therefore crucial for water resources management. For this purpose, estimating annual forest evapotranspiration is required. We developed an empirical model for estimating annual forest evapotranspiration E in Japan based on 43 catchment water balance datasets summarized from earlier publications. The model formulated E as E (mm) = 31.4T (°C) + 376, where T is mean annual air temperature. This model estimated E observed in forest catchments with an average 6% error relative to incident annual precipitation. This error was comparable to or smaller than the error included in precipitation data due to the spatial heterogeneity of precipitation. High-quality air temperature data are commonly available in Japan, thus this model is a practical tool for annual water yield estimates from forested areas and therefore water resources management..
122. H. Komatsu, T. Kume, K. Otsuki, Contemporary role of catchment water balance data for forest evapotranspiration research, Nihon Ringakkai Shi/Journal of the Japanese Forestry Society, 89, 5, 346-359, 2007.12, Recently, catchment water balance measurements have not been used actively for examining forest evapotranspiration compared to process-based measurements based on meteorological and sap-flow methods. This paper overviewed the history of forest evapotranspiration studies and clarified what caused this situation. This paper then pointed out that catchment water balance measurements cannot be replaced completely by process-based measurements from the viewpoints of data accuracy and feasibility of measurements. This paper also pointed out that coordination of process-based measurements and catchment water balance measurements brings new insights. Furthermore, this paper proposed several important topics that should be examined by such coordination and also proposed measures to develop environments that promote such coordination..
123. Hikaru Komatsu, Ayumi Katayama, Shigeki Hirose, Atsushi Kume, Naoko Higashi, Shigeru Ogawa, Kyoichi Otsuki, Reduction in soil water availability and tree transpiration in a forest with pedestrian trampling, Agricultural and Forest Meteorology, 10.1016/j.agrformet.2007.04.014, 146, 1-2, 107-114, 2007.09, Many studies have reported tree growth reduction in forests with pedestrian trampling, implying a reduction of tree transpiration in such forests. We undertook observations of tree transpiration based on the heat-pulse method in a forest (Lithocarpus edulis) with pedestrian trampling. We prepared trampled and control plots in the forest. Tree transpiration in the trampled plot was reduced compared to that in the control plot after precipitation with a small-precipitation period preceding this. No difference was observed between plots in the small-precipitation period itself; during which tree transpiration was limited in both plots. After the period, tree transpiration recovery was not as complete in the trampled plot as in the control plot. This was caused by incomplete soil matric potential recovery at 20 cm and deeper in the trampled plot due to a lower infiltration rate. We believe this study is the first to report reduction of tree transpiration in a forest with pedestrian trampling..
124. Yoshiyuki Miyazawa, Kihachiro Kikuzawa, Kyoichi Otsuki, Decrease in the capacity for RuBP carboxylation and regeneration with the progression of cold-induced photoinhibition during winter in evergreen broadleaf tree species in a temperate forest, Functional Plant Biology, 10.1071/FP06312, 34, 5, 393-401, 2007.05, We measured the photosynthetic capacity (RuBP carboxylation and electron transport capacity at 25°C) and the maximum photochemical efficiency (F v/Fm) from autumn to spring in saplings of two evergreen broadleaf tree species and examined the negative effects of photoinhibition on the photosynthetic capacity. Saplings were grown in pots under three simulated natural light environments typical of temperate forests: an open site, deciduous understorey and evergreen understorey. During winter, the photosynthetic capacity and Fv/Fm synchronously decreased in leaves in the sun, but not those in the shade. We found large differences in F v/Fm and photosynthetic capacity, along with a positive correlation between Fv/Fm and the photosynthetic capacity among leaves in different light environments. In photoinhibited leaves that were transferred to the shade in mid-winter, photosynthetic capacity increased synchronously with the increment of Fv/Fm. The decrease in photosynthetic capacity in photoinhibited leaves and the synchronous recovery of photosynthetic capacity with photoinhibition supported the hypothesis that photoinhibition depressed the photosynthetic capacity during winter. We showed that difference in the degree of photoinhibition was responsible for the different winter photosynthetic capacity among leaves exposed to different light environments..
125. Sheng Du, Norikazu Yamanaka, Fukuju Yamamoto, Kyoichi Otsuki, Shengqi Wang, Qingchun Hou, The effect of climate on radial growth of Quercus liaotungensis forest trees in Loess Plateau, China, Dendrochronologia, 10.1016/j.dendro.2007.01.005, 25, 1, 29-36, 2007.05, Annual ring growth of Quercus liaotungensis trees in natural forests bounded by desertified region in the Loess Plateau of China was investigated for the evidence of climatic influence. Increment cores were sampled and cross-dated for 120 trees from six stands 0.5-2.5 km apart. Site tree-ring chronologies were created using general dendrochronological techniques. The results of correlation analyses between tree-ring indices and monthly climatic variables indicated that radial growth was positively correlated with precipitation in September of the previous year and that from April to June of the current year. Ring widths were negatively affected by temperature during spring and summer. In contrast, mild temperature in the previous October showed a positive influence. The results suggest that precipitation is important in the early growing season when soil and air are dry, and that high temperatures tend to reduce radial growth in this region. September rainfalls and a warm October may provide conditions that facilitate carbon storage, favor soil microbial activity, and promote root growth and shoot maturation against detrimental effects of stresses in the following seasons. There were also some differences among plots in the effects of both climatic variables probably as a result of different structures and geographical conditions that modified microenvironments. The results may contribute to the reforestation management of the area. It is expected that Q. liaotungensis forests should be ecologically established in this region on shady and half-shady slopes where air and soil drought stresses are not serious..
126. Komatsu, H., Katayama, A., Kume, T. and Otsuki K. , Sap-flow velocity reduction by soil water deficit observed in a Lithocarpus edulis forest on Kyushu Island, Japan, Bulletin of Kyushu University Forest. , 88, 21-31, 2007.03.
127. Ryunosuke Tateno, Naoko Tokuchi, Norikazu Yamanaka, Sheng Du, Kyoichi Otsuki, Tetsuya Shimamura, Zhide Xue, Shengqi Wang, Qingchun Hou, Comparison of litterfall production and leaf litter decomposition between an exotic black locust plantation and an indigenous oak forest near Yan'an on the Loess Plateau, China, Forest Ecology and Management, 10.1016/j.foreco.2006.12.026, 241, 1-3, 84-90, 2007.03, Litterfall production, the amount of organic matter on the forest floor, and litter decomposition rates were studied in an exotic nitrogen (N)-fixing black locust (Robinia pseudoacacia) plantation and an indigenous non-N-fixing oak (Quercus liaotungensis) forest near Yan'an, on the Loess Plateau, China. The chemical composition of litterfall and soil was also examined. Litterfall production was similar in the two forests; however, the amount of N in litterfall was greater in the black locust plantation than in the oak forest because of the high N concentration of black locust leaves. The decomposition rate of black locust leaves was higher than that of oak leaves, most likely because of the higher N content of black locust leaves. These results suggested that N cycling was greater and faster in the black locust plantation than in the oak forest. However, faster decomposition caused the disappearance of the organic layer from the forest floor in the black locust plantation. Furthermore, despite greater N cycling in the black locust plantation, the soil N content was lower than in the oak forest. Our results indicated that the black locust plantation might be more susceptible to soil erosion than the oak forest. In addition, our study suggested that the black locust plantation had advantages in short-term N uptake, growth, and N cycling; however, it had disadvantages in soil development and regeneration and sustainable land management..
128. Chemical characteristics of precipitation and streamwater at the Ashoro Research Forest and Kasuya Research Forest.
129. Jun'ichiro Ide, Osamu Nagafuchi, Masaaki Chiwa, Atsushi Kume, Kyoichi Otsuki, Shigeru Ogawa, Effects of discharge level on the load of dissolved and particulate components of stream nitrogen and phosphorus from a small afforested watershed of Japanese cypress (Chamaecyparis obtusa), Journal of Forest Research, 10.1007/s10310-006-0250-7, 12, 1, 45-56, 2007.02, The behavior of dissolved and particulate components of stream nitrogen (N) and phosphorus (P) were measured for 2 years in a small mountainous watershed covered primarily with a plantation forest of Japanese cypress (Chamaecyparis obtusa). The load of dissolved N and P bore a consistent relationship to discharge while the load of particulate N and P varied by up to two orders of magnitude at a given discharge level. Most N was exported in a dissolved form (DN) while most P was exported in a particulate form (PP), which bears similarity to loads from agricultural watersheds. Owing to the different behaviors of DN and PP, changes in the total nitrogen (TN) load were primarily attributed to variations in discharge unlike changes in the total phosphorus (TP) load. High flow conditions, resulting from heavy rainfall, displayed PP release significantly larger than expected. The TP load in high flow conditions was severely underestimated using a regression equation expressed as a function of discharge, which was based on the weekly sampling data biased toward low flow conditions. In addition, the TN load during peak discharges in heavy rain events was underestimated by the regression equation because of unpredictable increases in the particulate component. Our study shows that the particulate component ratio determines whether discharge can explain changes in load regardless of chemical species. The results suggest that plantation forests in rainy regions can be a diffuse source of particulate nutrients depending on soil surface conditions..
130. Tomo'omi Kumagai, Sayaka Aoki, Takanori Shimizu, Kyoichi Otsuki, Sap flow estimates of stand transpiration at two slope positions in a Japanese cedar forest watershed, Tree physiology, 10.1093/treephys/27.2.161, 27, 2, 161-168, 2007.02, We determined the amount of information needed to estimate watershed-scale transpiration in a Japanese cedar (Cryptomeria japonica D. Don) forest from sap flow measurements of individual trees. Measurements of tree biometrics (diameter at breast height (DBH) and tree sapwood area (AS_tree)), and tree-to-tree and radial variations in xylem sap flux density (Fd) were made in two stand plots, an upper slope plot (UP) and a lower slope plot (LP), during a growing season characterized by significant variations in environmental factors. We then investigated how mean stand sap flux density (JS) and a tree stem allometric relationship (DBH-AS_tree) varied between the stands. Appropriate sample sizes for estimating representative JS values were determined. Both a unique and a general function allowed description of the allometric relationship along the slope, but the data for its formulation was required for both the UP and LP. Values of JS in the UP and LP were similar during the study period despite differences in tree density and size between the plots, implying that J S measured in a partial stand in a watershed is a reasonable estimate of JS in other stands in the watershed, and that stand sapwood area calculated from AS_tree is a strong determinant of water use in a forest watershed. To estimate JS in both the UP and LP, it was necessary to sample at least 10 trees in each plot..
131. Yoshiyuki Miyazawa, Shirasa Tatsuya, Kihachiro Kikuzawa, Kyoichi Otsuki, The light environment, morphology and growth of the early successional tree species Litsea citriodora, Forest Ecology and Management, 10.1016/j.foreco.2006.09.010, 236, 2-3, 251-258, 2006.12, The light environment and growth traits of the pioneer tree species Litsea citriodora in a recently clear-cut plantation were investigated in order to reveal the establishment process and growth of this species under annual weeding after clear-cutting. We investigated the light environments and the morphology, physiology and aboveground architecture of L. citriodora saplings in a plot that included both clear-cut open areas and forest floor under a conifer canopy. Dense populations of L. citriodora saplings were found in the open sites but few were observed on the forest floor. Saplings that originated from old stumps (sprout-saplings) were tall in height and dense, but seedlings were sparse and lower in height than the competitive tall herbaceous species Solidago altissima. Saplings of L. citriodora showed a higher leaf area per aboveground mass and greater area-based photosynthetic capacity than saplings of the co-occurring pioneer tree species Mallotus japonicus and Clerodendron trichotomum. Moreover, the L. citriodora saplings had a main stem with a larger length per mass ratio and more efficiently elongated per unit aboveground mass than M. japonicus and C. trichotomum. Sprout-saplings of L. citriodora attained rapid vertical elongation with rapid biomass acquisition as a result of their aboveground shoot architecture, allowing competition with S. altissima. Clear-cutting and subsequent weeding not only created open sites favorable for this pioneer tree, but also promoted the formation of sprouts, allowing sprout-saplings with rapid vertical growth to successfully establish in the clear-cut zone by inhibiting complete coverage by other pioneer trees..
132. Otsuki, K., Yamanaka, N., Du, S., Yamamoto, F., Xue, Z., Wang, S. and Hou, Q., Seasonal Changes of Forest Ecosystems in an Artificial Forest of Robinia pseudoacacia in the Loess Plateau in China, Journal of Agricultural Meteorology, 60( 5), pp.613-616, 2006.02.
133. Kumagai, T., Aoki, S., Nagasawa, H., Mabuchi, T., Kubota, K., Inoue, S., Utsumi, Y. and Otsuki, K., Effects of tree-to-tree and radial variations on sap flow estimates of transpiration in Japanese cedar, Agricultural and Forest Meteorology, 10.1016/j.agrformet.2005.11.007, 135, 1-4, 110-116, 135(1-4), pp.110-116, 2005.12.
134. Kumagai, T., Nagasawa, H., Mabuchi, T., Ohsaki, S., Kubota, K., Kogi, K., Utsumi, Y., Koga, S. and Otsuki, K., Sources of error in estimating stand transpiration using allometric relationships between stem diameter and sapwood area for Cryptomeria japonica and Chamaecyparis obtusa, Forest Ecology and Management, 10.1016/j.foreco.2004.10.066, 206, 1-3, 191-195, 206, pp.191-195, 2005.02.
135. Shigeki Hirose, Atsushi Kume, Shinichi Takeuchi, Yasuhiro Utsumi, Kyoichi Otsuki, Shigeru Ogawa, Stem water transport of Lithocarpus edulis, an evergreen oak with radial-porous wood, Tree physiology, 10.1093/treephys/25.2.221, 25, 2, 221-228, 2005.02, The stem water conducting system of an evergreen broad-leaved oak, Lithocarpus edulis (Mak.) Nakai, was investigated. Evergreen broad-leaved oaks (Lithocarpus, Castanopsis, Cyclobalanopsis, Quercus) belonging to the Quercoideae are a major component of Asian monsoon forests, and are characterized by the possession of radial-porous wood. A characteristic of radial-porous wood is the development of aggregate rays between radially oriented files of vessels. We measured the distribution of vessel lumen diameters in a stem cross section and calculated the theoretical water conductivity of the wood. The radial profile of the heat pulse velocity (HPV) was measured for an intact whole tree under field conditions and compared with the theoretical distribution of water conductivity. Soft X-ray photographs of frozen stem sections indicated that most of the vessel lumina were filled with water, including those of vessels more than 20 years old. Even when vessels were relatively wide (lumen diameters > 100 μm), cavitation was negligible. The rate of water uptake from the cut stem base correlated closely with HPV (r = 0.96), and HPV closely reflected the mean volume flow per stem sectional area (SFV
) around the sensor probes. However, the ray tissue sharply inhibited heat transfer, and the positioning of the probes strongly affected the absolute value of HPV. It was also found that HPV more closely reflected the mean sap flow velocity in the vessels than did SFV
136. Sato, Y., Kumagai, T., Kume, A., Otsuki, K. and Ogawa, S., Experimental analysis of moisture dynamics of litter layers - the effects of rainfall conditions and leaf shapes-, Hydrological Process, 10.1002/hyp.5746, 18, 16, 3007-3018, 18(16), pp.3007-3018, 2004.11.
137. Matsuno, Y., Tasumi, M., Van der Hoek, W., Sakthivadivel, R. and Otsuki, K., Analysis of return flows in a tank cascade system in Sri Lanka, Paddy and Water Environment, 10.1007/s10333-003-0029-9, 1, 4, 173-181, 1(4), pp.173-181, 2003.12.
138. Kengo Ito, Tomoyasu Ezuka, Kyoichi Otsuki, Makio Kamichika, Water Shortage and Salinization Diagnosis of the Grass by Spectral Reflectance, Journal of Agricultural Meteorology, 10.2480/agrmet.59.199, 59, 2, 199-204, 2003.01, In this paper, we tried to diagnose the stress that was brought by water shortage and salinization by spectral reflectance. The concentration of chlorophyll and leaf water content with raw leaf of grass was changed by these stresses. Spectral reflectance was influenced by the stresses too. But the pattern of spectral curve changes was not the same for water shortage and salinization. The concentration of chlorophyll was decreased similarly by both stresses. On the other hands, the leaf water content was extremely decreased by water shortage compared to salinization. We couldn't learn the cause of stress using the concentration of chlorophyll as the only index of stress. It is necessary for diagnosis of stress that both concentration of chlorophyll and leaf water content be applied as the indexes of stress. The concentration of chlorophyll and leaf water content could be measured by spectral reflectance not concerned with the kind of stress. The concentration of chlorophyll was estimated by R800nm/R680nm. The leaf water content was estimated by R1200 nm/R1500nm. Application of these indexes makes possible the diagnosis of water shortage and salinization stress by remote sensing..
139. Hirokazu Haga, Tomo'omi Kumagai, Kyoichi Otsuki, Shigeru Ogawa, Transport and retention of coarse woody debris in mountain streams
An in situ field experiment of log transport and a field survey of coarse woody debris distribution, Water Resources Research, 38, 8, 11-116, 2002.08, Although coarse woody debris (CWD) is an important component of stream ecosystems in forested areas, the processes of CWD distribution, transport, and retention have not been clarified. In this study the distribution process of CWD pieces shorter than the bankfull width (S-CWD) is discussed using an in situ field experiment of log transport and a field survey of CWD distribution in mountain streams. The transport experiment showed that transport distance has a close relation to flow depth and also implied that the magnitude and sequence of a series of flows were important factors for S-CWD transport and retention in streams. The survey of CWD distribution indicated that in-stream obstructions played an important role in the S-CWD retention in deeper channels where S-CWD pieces were potentially transported distances more than spacing between trapping sites of CWD. Overall, the in situ field experiment and the segment- to reach-scaled analysis using h* (=depth/diameter) helped us understand the actual movement and distribution of CWD..
140. Song Gu, Kyoichi Otsuki, Makio Kamichika, Estimation of Daily Albedo on Tottori Sand Surface, journal of agricultural meteorology, 10.2480/agrmet.57.1, 57, 1, 1-10, 2001.09, Daily albedos of a bare sand surface were measured with a solarimeter (Eko MS-62) between 23 August and 30 November in 1997 at Tottori sand dune, Japan. These quickly decreased on rainy days, and recovered during dry spells (days between rainfalls). A strong exponential relationship was found between daily albedos and the number of dry days. The daily albedos on dry days also showed a direct relationship with daily transmissivities in the range less than 0.55. Two simple models were developed to estimate daily albedos for dry spell days on bare Tottori sand surface using routinem eteorological data. Daily albedos were calculated using these two models, and compared with the measured daily albedos. For Model #1, the daily albedos were successfully predicted only using the number of dry spell days; the correlation coefficient between the estimated and measured albedo was 0.73, and the standard error was 1.2%. For Model #2, the number of dry spell days and transmissivity were considered in order to calculate the daily albedo on dry spell days; the correlation coefficien was 0.85, and the standard error was 0.9%. Estimated albedos were in good agreement with measured albedos..
141. Song Gu, Kyoichi Otsuki, Maklo Kamichika, Albedo Characteristics of Tottori Sand Dune, journal of agricultural meteorology, 10.2480/agrmet.56.217, 56, 3, 217-225, 2000.09, The albedo of Tottori sand dune was measured with a solarimeter (Eko MS-62) and recorded by a data logger Solac-III (Eko). The soil water content (g/g) was measured at various depths a 9:00 a.m. every day. The relationships of albedo with soil water content and solar elevation were determined. The albedo changes with soil water content at the surface and at individual depths by two an three steps, respectively. The albedo decreased linearly with increasing surface soil water content over a small range. Outside that range, the albedo was essentially constant. The albedo appeared to be related strongly to solar elevation in the afternoon on clear days (transmissivity more than 0.55) when the surface soil water content was less than 0.005 g/g at 9:00. This relationship did not exist in the forenoon period due to dew condensation on the sand surface at night. However, the daily distribution of albedo appears to be approximately symmetrical about solar noon in response to solar elevation effects if the soil water content at sunrise is less than 0.005 g/g..
142. Tamon Tsujii, Naru Takayama, Seiji Hayakawa, Makio Kamicmka, Kyoichi Otsuki, The Properties of Turbulence in and above a Sorghum Canopy with 2nd Order Closure Model, journal of agricultural meteorology, 10.2480/agrmet.56.303, 56, 4, 303-310, 2000.09, Most meteorologists have reported that higher order closure models are better than the K-theory model for estimation of environment in the canopy, but solving a higher order closure model requires boundary conditions for turbulence, which is measured directly by a sonic anemometer. However, sonic anemometers are expensive so few scientists in agriculture use high order closure models. In the present research, estimation of the wind profile in and above a sorghum canopy was carried out by use of a 2nd order closure model with mean wind velocity at a single height above the canopy. Comparison between the observed and calculated profiles indicated that the former was well represented by the latter in general. This indicates that the present calculation scheme can be used for estimation of wind profiles in the canopy without observation of the turbulence. It revealed that most large scale turbulence was generated at the upper part of a sorghum canopy during the heading stage, and that measuring the plant area density should be a more important canopy meteorological observation than the leaf area index during theheading stage, since the non-leaf portion of plant area is not negligible..
143. Yasushi Abe, Kyoichi Otsuki, Makio Kamichika, Estimation of Water Quantity Recycled by Earth-Air Heat Exchange Distillation, journal of agricultural meteorology, 10.2480/agrmet.55.101, 55, 2, 101-108, 1999.01, The authors have developed a “Earth-Air Heat Exchange Distillation System” for collecting water from vapor originated in evapotranspiration. This system distills water from vapor by cooling the air in a greenhouse, using underground heat exchange pipes. It is similar to “Soil Heat Exchanger-Storage Systems”. A parameter for estimating the daily amount of collected water was investigated, based on heat and vapor budget of the heat exchange pipe. The results indicate that the daily amount of collected water is a linear function of the integrated surplus of air-soil temperature..
144. Reiji Kimura, Kyoichi Otsuki, Makio Kamichika, , Relationships between the Zero-plane Displacement and the Roughness Length over Sorghum and Alfalfa Canopies, Journal of Agricultural Meteorology, 10.2480/agrmet.55.15, 55, 1, 15-24, 1999.01, The effect of wind speed on the aerodynamical parameters, namely the zero-plane displacement d and roughness length z0, and the relationships between d and z0 is discussed. Experiments conducted in sorghum and alfalfa fields reveal that d decreases and z0 increases with increasing wind speed or friction velocity. The relations between d and z0 obtained in these experiments are not well expressed by previous equations that were presented during the last several decades. Thus, new equations representing the relationships between d and z0, and a newly designed concept for eddy viscosity within the canopy are proposed and experimentally tested in sorghum, alfalfa, and tanukimame fields. The test results demonstrate that calculations from present equations coincide with the observed results. In the tanukimame field, however, the zero-plane displacement and roughness length do not vary with wind speed when the leaf area index LAI is large (LAI=5.6). On this point, it is considered that the dependence of the zero-plane displacement and roughness length on wind speed are influenced by the leaf area index and the drag coefficient for an individual leaf..
145. Reiji Kimura, Junsel Kondo, Kyolchl Otsuki, Yasutaka Kihara, A Leaf Bulk Transfer Coefficient Model for Latent Heat Flux and its Application to a Lawnland, journal of agricultural meteorology, 10.2480/agrmet.53.307, 53, 4, 307-314, 1997.09, A leaf bulk transfer coefficient for latent heat flux ce has been formulated as a function of solar radiation, wind speed, and minimum stomatal resistance, and time variations of the sensible heat flux H and the latent heat flux lE over a lawnland for a period of summer three months have been simulated using routine meteorological data(AMeDAS). The calculated results agree well with the observed values: the rms error between the observed and the calculated values of H are ±8 Wm-2, while those of lE are ± 12 Wm-2..
146. Kengo Ito, Kyoichi Otsuki, Makio Kamichika, Analysis of the perpendicular structure of vegetation by spectral reflectance in the visible and near infrared, journal of agricultural meteorology, 10.2480/agrmet.52.567, 52, 5, 567-570, 1997.01, The analysis of the perpendicular structure of vegetation by remote sensing would provide valuable information for classification of vegetation and estimation of the environment. The purpose of this paper is to investigate the relationship between perpendicular structure of vegetation and spectral reflectance in visible and near infrared. The spectral reflectance is measured in the range of 400nm to 2500nm at intervals of 1nm by changing the number of overlap leaves, perpendicular space between leaves, angle of leaf, incident angle and sensor look angle. The results indicate the following features. First, spectral reflectance in red and near infrared increases with increasing the number of overlap leaves and narrowing the perpendicular space between leaves, but visible rays are not affected by these factors. Secondly, when the perpendicular space between leaves is wide, the spectral reflectance is affected by incident angle. Thirdly, the changes of spectral reflectance differ with leaf angle. These results lead to the conclusion that the relationship between those parameters is complex..
147. Reiji Kimura, Junsei Kondo, Kyoichi Otsuki, Makio Kamichika, Estimation of Bulk Transfer Coefficient and Surface Moisture Availability on a Sorghum Field in Sand Dune, Journal of Agricultural Meteorology, 10.2480/agrmet.53.131, 53, 2, 131-140, 1997.01, The bulk transfer method combined with the heat balance equation of the surface requires the bulk transfer coefficient for sensible heat flux CHU and the surface moisture availability β (evapotranspiration efficiency) to evaluate the surface temperature Ts, sensible heat flux H and latent heat flux lE, respectively. This paper examines relations between these coefficients and various factors (soil moisture content, solar radiation). Meteorological observations on a sorghum field in Tottori sand dune were carried out for 6-28 August, 1994. Significant results of the observations are the followings: 1) The value of bulk transfer coefficient varied with the atmospheric stability. 2) The value of β increased with increasing solar radiation, and tended to a constant value (β=0.35) when the solar radiation exceeded about 600 Wm-2. 3) The value of β increased according to the soil moisture content. Observations of Ts, H and lE were compared with the simulations with the single source model (Kondo and Watanabe, 1992). This model simulates well the observed values of the daily mean of Ts, H and lE within an error of about±20 Wm-2,±20 Wm-2 and ±1.1°C, respectively..
148. Yasushi Abe, Kyoichi Otsuki, Makio Kamichika, Estimation of Surface Soil Water Content of Sand Dune at Night, Journal of Agricultural Meteorology, 10.2480/agrmet.53.185, 53, 3, 185-190, 1997.01, It is well known that soil water content at the surface of sand increases at night, which is dry in the daytime. The mechanism of this phenomenon, however has not quantitatively clarified because continuous measurement of nighttime soil water content is very difficult. Thus, in this study, the method to estimate nighttime surface soil water content was examined by using the meteorological and soil physical data measured at Tottori sand dune in 1995. Albedo of the infrared radiation and thermal conductivity of the sand surface, which are readily calculable, were selected as the parameters of the estimation equation. Albedoes can calculate from the surface temperatures of sand measured by thermocouple and radiation thermometer, and sky temperature measured by radiation thermometer. Thermal conductivities can calculate from the radiation balance, heat balance, and temperature gradient at soil surface. The results show that thermal conductivities would give satisfying estimations of surface soil water content of sand surface..
149. Kyoichi Otsuki, Naruo Mushiake, Studies on Monitoring Land and Water Management in Pakistan, Journal of Agricultural Meteorology, 10.2480/agrmet.52.665, 52, 5, 665-668, 1997.01, The purpose of this study is to monitor land and water management using remote sensing and Geographical Information System (GIS). The Fourth Drainage Project, which is located in the center of Punjab Province of Pakistan, was selected as a research field. The Project was launched in 1983 to combat the twin menace of waterlogging and salinity; the depth of the water table in 77% of the area was 0-1.5m, and 43% of the land was saline. A newly introduced subsurface drainage system and a remodeled surface drainage system by the project have gradually reduced the waterlogging problem. The salinity problem, however, still remains. Analyzing Landsat-TM, GIS and ground truth data, following results were obtained. Waterlogging and salinity problems are mainly distributed along the drainage canals. The main reason is that the water table along the drainage canals is shallower due to the relatively low location. The Normalized Difference Vegetation Index (NDVI) tends to be lower along drainage canals and higher along the irrigation canals. It is mainly because of the unbalance of water distribution as a result of the locational disadvantage of downstream farmers. By contrast, an enterprise farm near the project does not show these locational unbalances but exhibits high NDVI values almost all over the farm, except for fallow. It is due to the fact that the water management there is demand-oriented, thus more flexible, and sufficient water is supplied..
150. Jian zhong Zhou, Kyoichi Otsuki, Makio Kamichika, Climatological evaluation of agricultural productivity using chikugo model
Case study of inner mongolia in china, Journal of Agricultural Meteorology, 10.2480/agrmet.51.21, 51, 1, 21-26, 1995.01, Chikugo model, which was originally the climatological model to estimate Net Primary Productivity (NPP) of natural vegetation including underground organs, was applied to estimate agricultural productivity in Inner Mongolia in China. The results show that the natural grass productivity and the agricultural crop (cereals, pulse crops and potato) productivity under poor irrigation activities are linearly correlated with NPP. Agricultural crop productivity under various irrigation ratios (irrigated area divided by cropping area) are not directly related with NPP. However, the rates of agricultural crop productivity to NPP are linearly correlated with irrigation ratios. Therefore, Chikugo model can be applicable to evaluate the potential productivity of both natural grassland and farmland, and offer an index of the proper agricultural development..
151. Makio Kamichika, Tahei Yamamoto, Kyoichi Otsuki, Yasushi Abe, Recycling Use of Irrigated Water by Earth-air Heat Exchange Distillation, journal of agricultural meteorology, 10.2480/agrmet.48.667, 48, 5, 667-669, 1993.05, This paper deals with saving water resources and improving irrigation water quality for agricultural development in and areas. An experiment on the recycling use of irrigated water using earth-air heat exchange distillation is described. The experimental apparatus is similar to a solar greenhouse using underground heat exchange. The air in the greenhouse which is nearly saturated by plant transpiration is refrigerated along the underground pipe and the vapour in it is condensed into waterdrops. The condensed water is collected. This recovered water is water distilled from the moist air, which is originally from irrigated water, and is available for re-use in irrigation. The experiment was carried out in the vinyl film tunnel culture with lettuce plant. In the experiment, 30% of the supplied water was recovered. In addition to the re-use of this water, the vapor retentivity of the vinyl film can also result in a water savings of about 40% in comparison with open-field culture. Furthermore, it is expected that the accumulation of salt in soils can be reduced to about 40% compared with open-field culture conditions, because of the high quality of the distilled water which was recovered is mixed with irrigation water..