40) Ikawa, H., Nakai, T., Busey, R.C., Harazono, Y., Ikeda, K., Iwata, H., Nagano, H., Saito, K., Ueyama, M., Kobayashi H. (2024) Interannual variations in spring snowmelt timing of Alaskan black spruce forests using a bulk‐surface energy balance approach. Water Resources Research 60(5), e2023WR035984. [Link]

<Summary> We constructed a simple snowmelt model that treats the ecosystem surface as a single bulk layer. Energy fluxes across this bulk surface and the snow-soil boundary determine snow temperature and the energy utilized for snowmelt, bypassing the needs for detailed canopy information. Applying the model to decadal observation data from Alaskan boreal forests, we found that snowfall, air temperature, and atmospheric radiation were important meteorological drivers for explaining interannual variations in snowmelt timing. 

39) Bowling, D.R., Schädel, C., Smith, K.R., Richardson, A.D., Bahn, M., Arain, M.A., Varlagin, A., Ouimette, A.P., Frank, J.M., Barr, A.G., Mammarella, I., Šigut, L., Foord, V., Burns, S.P., Montagnani, L., Litvak, M.E., Munger, J.W., Ikawa, H., Hollinger, D.Y., Blanken, P.D., Ueyama, M., Matteucci, G., Bernhofer, C., Bohrer, G., Iwata, H., Ibrom, A., Pilegaard, K., Spittlehouse, D.L., Kobayashi, H., Desai, A.R., Staebler, R.M., Black, T.A. (2024) Phenology of Photosynthesis in Winter-Dormant Temperate and Boreal Forests: Long-Term Observations From Flux Towers and Quantitative Evaluation of Phenology Models. Journal of Geophysical Research, Biogeosciences 129(5), e2023JG007839. [Link]

38) Noshiro, T. Nomura, D., Kondo, F., Ono, K., Else., B., Ikawa, H. (2024) Comparisons of different sample air-drying systems for carbon dioxide flux measurements based on eddy covariance in cold environments. Journal of Agricultural Meteorology 80(1), 22-28. [Link]

37) Miller, E. A., Iwata, H., Ueyama, M., Harazono, Y., Kobayashi, H., Suzuki, R., Ikawa, H., Busey, R., Iwahana, G., Euskirchen, E. S. (2023) Evaluating the drought code for lowland taiga of interior Alaska using eddy covariance measurements and the advection-aridity approach, International Journal of Wildland Fire 32(8) 1226-1243. [Link]

36) Watts, J. D., Farina, M., Kimball, J. S., Schiferl, L. D., Liu, Z., Arndt, K. A., Zona, D., Ballantyne, A., Euskirchen, E. S., Parmentier, F.-J. W., Helbig, M., Sonnentag, O., Tagesson, T., Rinne, J., Ikawa, H., Ueyama, M., Kobayashi, H., Sachs, T., Nadeau, D. F., Kochendorfer, J., Jackowicz-Korczynski, M., Virkkala, A., Aurela, M., Commane, R., Byrne, B., Birch, L., Johnson, M. S., Madani, N., Rogers, B., Du, J., Endsley, A., Savage, K., Poulter, B., Zhang, Z., Bruhwiler, L. M., Miller, C., Goetz, S., Oechel, W. C. (2023) Carbon Uptake in Eurasian Boreal Forests Dominates the High Latitude Net Ecosystem Carbon Budget. Global Change Biology 29, 1870-1889. [Link]

35) Zhang, G., Ujiie, K., Yoshimoto, M., Sakai, H., Tokida, T., Usui, Y., Wakatsuki, H., Arai, M., Ikawa, H., Nakamura, H. (2022) Daytime warming during early grain filling offsets the CO2 fertilization effect in rice. Environmental Research Letters 17(11), 114051. [Link]

34) El-Amine, M., Roy, A., Koebsch, F., Baltzer, J.L., Barr, A., Black, A., Ikawa., H., Iwata, H., Kobayashi, H., Ueyama, M., Sonnentag, O., (2022) What explains the year-to-year variation in growing season timing of boreal black spruce forests? Agricultural and Forest Meteorology 324 (15) 109113. [Link]

33) Nomura, D., Ikawa, H., Kawaguchi, Y., Kanna, N., Kawakami, T., Nosaka, Y., Umezawa, S., Tozawa, M., Horikawa, T., Sahashi, R., Noshiro, T., Kaba, I., Ozaki, M., Kondo, F., Ono, K., Yabe, I., Son, E.Y., Toyoda, T., Kameyama, S., Wang, C., Obata, H., Ooki, A., Ueno, H., Kasai, A. (2022) Atmosphere-sea ice-ocean interaction study in Saroma-ko Lagoon, Hokkaido, Japan 2021（北海道サロマ湖における大気–海氷–海洋相互作用研究について) Bulletin of Glaciological Research 40, 1-17. [Link]

32) Fushimi, E., Yoshida, H., Yabe, S., Ikawa, H., and Nakagawa, H. (2021) A quantitative staging system for describing rice panicle development and its application for a crop phenological model. Agronomy Journal 13(6), 5040-5053. [Link]

31) Migliavacca, M., Musavi, T., Mahecha, M.D., Nelson, J.A., Knauer, J., Baldocchi, D.D., Perez-Priego, O., Christiansen, R., Peters, J., Anderson, K., Bahn, M., Black, T.A., Blanken, P.D., Bonal, D., Buchmann, N., Cladararu, S., Carrara, A., Carvalhais, N., Cescatti, A., Chen, J., Cleverly, J., Cremonese, E., Desai, A.R., El-Mandany, T.S., Farella, M.M., Fernández-Martínez, M., Filippa, G., Forkel, M., Galvagno, M., Gomarasca, U., Gaugh, C.M., Gockede, M, Ibrom, A., Ikawa, H., Janssens, I.A., Jung, M., Kattge, J., Keenan, T.F., Knohl, A., Kobayashi, H., Kraemer, G., Law, B.E., Liddell, M.J., Ma, X., Mammarella, I., Martini, D., Macfarlane, C., Matteucci, G., Montagnani, L., Pabon-Moreno, D.E., Panigada, C., Papale, D., Pendall, E., Penuelas, J., Phillips, R.P., Reich, P.B., Rossini, M., Rotenberg, E., Scott, R.L., Stahl, C., Weber, U., Wohlfahrt, G., Wolf, S., Wright, I.J., Yakir, D., Zaehle, S., Reichstein, M. (2021) The three major axes of terrestrial ecosystem function. Nature 598, 468-472. [Link]

30) Watts, J.D., Natali, S.M., Minions, C., Risk, D., Arndt, K., Zona, D., Euskirchen, E.S., Rocha, A.V., Sonnentag, O., Helbig, M., Kalhori, A., Oechel, W., Ikawa, H., Ueyama, M., Suzuki, R., Kobayashi, H., Celis, G., Schuur, E.A.G., Humphreys, E., Kim, Y., Lee, B.Y., Goetz, S., Madani, N., Schierl, L.D., Commane, R., Kimball, J.S., Liu, Z., Torn, M.S., Potter, S., Wang, J.A., Jorgenson, M.T., Xiao, J., Li, X., Edgar, C. (2021) Soil respiration strongly offsets carbon uptake in Alaska and Northwest Canada. Environmental Research Letters 16, 084051. [Link]

29) Ikawa, H., Kuwagata, T., Haginoya, S., Ishigooka, Y., Ono, K., Maruyama, A., Sakai, H., Fukuoka, M., Yoshimoto, M., Ishida, S., Chen, C.P., Hasegawa, T., and Watanabe, T. (2021) Heat-Mitigation Effects of Irrigated Rice-Paddy Fields under Changing Atmospheric Carbon Dioxide based on a Coupled Atmosphere and Crop Energy-Balance Model. Boundary-Layer Meteorology 179, 447-476. https://doi.org/10.1007/s10546-021-00604-6 [link]

<Press Release by the National Agriculture and Food Research Organization and Hokkaido University>

<農研機構と北海道大学によるプレスリリース>

<北海道大学低温科学研究所　低温研ニュースレター>

<Summary> Paddy fields, which are popular as part of the typical landscapes of Asian countries including Japan, are known to have the effect of alleviating temperature rises in the paddy fields and surrounding areas - the function is known as a heat-mitigation effect. To understand this effect on regional temperature distributions, a regional land-atmosphere coupled model was developed, and its surface scheme for rice paddy areas was parameterized using data from the free-air CO2 enrichment (FACE) experiment reported by Ikawa et al. in 2018 and 2019. Using this model, we report that the heat-mitigation effect decreases under elevated CO2 due to the stomatal closure of rice plants. This impact on regionally averaged air temperature was found to be as significant as land use change.

28) Johnston, A.S.A., Meade, A., Ardö, J., Arriga, N., Black, T., Blanken, P.D., Bonal, D., Brümmer, C., Cescatti, A., Dušek, J., Graf, A., Gioli, B., Goded, I., Gough, C.M., Ikawa, H., Jassal, R., Kobayashi, H., Magliulo, V., Manca, G., Montagnani, L., Moyano, F.E., Olesen, J.E., Sachs, T., Shao, C., Tagesson, T., Wohlfahrt, G., Wolf, S., Woodgate, W., Varlagin, A., Venditti, C. (2021) Temperature thresholds of ecosystem respiration at a global scale. Nature Ecology & Evolution 5, 487-494. [link]

27) Chu, H., Luo, X., Ouyang, Z., Chan, W.S., Dengel, S., Biraud, S.C., Torn, M.S., Metzger, S., Kumar, J., Arain, M.A., Arkebauer, T.J., Baldocchi, D., Bernacchi, C., Billesbach, D., Black, T.A., Blanken, P.D., Bohrer, G., Bracho, R., Brown, S., Brunsell, N.A., Chen, J., Chen, X., Clark, K., Desai, A.R., Duman, T., Durden, D., Fares, S., Forbrich, I., Gamon, J.A., Gough, C.M., Griffis, T., Helbig, M., Hollinger, D., Humphreys, E., Ikawa, H., Iwata, H., Ju, Y., Knowles, J.F., Knox, S.H., Kobayashi, H., Kolb, T., Law, B., Lee, X., Litvak, M., Liu, H., Munger, J.W., Noormets, A., Novick, K., Oberbauer, S.F., Oechel, W., Oikawa, P., Papuga, S.A., Pendall, E., Prajapati, P., Prueger, J., Quinton, W.L., Richardson, A.D., Russell, E.S., Scott, R.L., Starr, G.G., Staebler, R., Stoy, P.C., Stuart-Haëntjens, E., Sonnentag, O., Sullivan, R.C., Suyker, A., Ueyama, M., Vargas, R., Wood, J.D., Zona, D. (2021) Representativeness of Eddy-Covariance Flux Footprints for Areas Surrounding AmeriFlux Sites. Agricultural and Forest Meteorology 301-302 108350. [link]

26) Zhang G., Sakai, H., Yoshimoto, M., Wakatsuki, H., Tokida, T., Ikawa, H., Arai, M., Nakamura, H., Hasegawa, T. (2021) Effect of foliar spray of kinetin on the enhancement of rice yield by elevated CO2. Journal of Agronomy and Crop Science 3, 535-543. [link]

25) Helbig, M., Waddington, J.M., Alekseychik, P., Amiro, B.D., Aurela, M., Barr, A.G., Black, T.A., Blanken, P.D., Carey, S.K., Chen, J., Chi, J., Desai, A.R., Dunn, A., Euskirchen, E.S., Flanagan, L.B., Friborg, T., Garneau, M., Grelle, A., Harder, S., Heliasz, M., Humphreys, E.R., Ikawa, H., Isabelle, P.-E., Iwata, H., Jassal, R., Korkiakoski, M., Kurbatova, J., Kutzbach, L., Lapshina, E., Lindroth, A., Löfvenius, M.O., Lohila, A., Mammarella, I., Marsh, P., Moore, P.A., Maximov, T., Nadeau, D.F., Nicholls, E.M., Nilsson, M.B., Ohta, T., Peichl, M., Petrone, R.M., Prokushkin, A., Quinton, W.L., Roulet, N.T., Runkle, B.R.K., Sonnentag, O., Strachan, I.B., Taillardat, P., Tuittila, E.-S., Tuovinen, J.-P., Turner, J., Ueyama, M., Varlagin, A., Vesala, T., Wilmking, M., Zyrianov, V., Schulze C. 2020. The biophysical climate mitigation potential of boreal peatlands during the growing season. Environmental Research Letters 15, 104004. [link]

24) Helbig, M., Waddington, J.M., Alekseychik, P., Amiro, B.D., Aurela, M., Barr, A.G., Black, T.A., Blanken, P.D., Carey, S.K., Chen, J., Chi, J., Desai, A.R., Dunn, A., Euskirchen, E.S., Flanagan, L.B., Forbrich, I., Friborg, T., Grelle, A., Harder, S., Heliasz, M., Humphreys, E.R., Ikawa, H., Isabelle, P.-E., Iwata, H., Jassal, R., Korkiakoski, M., Kurbatova, J., Kutzbach, L., Lindroth, A., Löfvenius, M.O., Lohila, A., Mammarella, I., Marsh, P., Maximov, T., Melton, J.R., Moore, P.A., Nadeau, D.F., Nicholls, E.M., Nilsson, M.B., Ohta, T., Peichl, M., Petrone, R.M., Petrov, R., Prokushkin, A., Quinton, W.L., Reed, D.E., Roulet, N.T., Runkle, B.R.K., Sonnentag, O., Strachan, I.B., Taillardat, P., Tuittila, E.-S., Tuovinen, J.-P., Turner, J., Ueyama, M., Varlagin, A., Wilmking, M., Wofsy, S.C., Zyrianov, V., 2020. Increasing contribution of peatlands to boreal evapotranspiration in a warming climate. Nature Climate Change 10, 555–560. [link] 

23) Sikma, M., Ikawa, H., Heusinkveld, B., Yoshimoto, M., Hasegawa, T., Haar, L. G., Anten, N., Nakamura, H.,  Vilà-Guerau de Arellano, J., Sakai, H., Tokida, T., Usui, Y., Evers, J. (2020) Quantifying the feedback between rice architecture, physiology and microclimate under current and future CO2 conditions. Journal of Geophysical Research, Biogeosciences 125, e2019JG00545. [link]

22) Yonemura, S., Kodama, N., Taniguchi, Y., Ikawa, H., Adachi, S., Hanba, Y.T. (2019) A high-performance system of multiple gas-exchange chambers with a laser spectrometer to estimate leaf photosynthesis, stomatal conductance, and mesophyll conductance. Journal of Plant Research 132, 705-718. [link]

21) Ikawa, H., Sakai, H., Chen, C.P., Soong, T.H., Yonemura, S., Taniguchi, Y., Yoshimoto, M., Tokida, T., Zhang, G., Kuwagata, T., Nakamura, H., Avenson, T.,  and Hasegawa, T. (2019) High mesophyll conductance in the high-yielding rice cultivar Takanari quantified with the combined gas exchange and chlorophyll fluorescence measurements under free-air CO2 enrichment. Plant Production Science 22(3) 395-406. [link]

<Summary> We utilized a new photosynthesis measurement device, the LI-6800, to investigate the photosynthesis rates of the high-yielding Takanari rice variety. Our findings indicate that the high rates of photosynthesis observed can be attributed to two factors: high stomatal conductance during the early growth stage and high mesophyll conductance during the later stages. We also discovered positive correlations between leaf nitrogen and both Vcmax and mesophyll conductance. While Vcmax is mostly explained by leaf nitrogen, other factors that we did not consider in this study would also be important for mesophyll conductance.

20) Hasegawa, T., Sakai, H., Tokida, T., Usui, Y., Nakamura, H., Wakatsuki, H., Chen, C.P., Ikawa, H., Zhang, G., Nakano, H., Yashima-Matsushima, M., and Hayashi, K. (2019) A high-yielding rice cultivar "Takanari" shows no N constraints on CO2 fertilization. Frontiers in Plant Science 10, 361. [link]

19) Saito, K., Iwahana, G., Ikawa, H., Nagano, H., Busey, R.C. (2018) Links between annual surface temperature variation and land cover heterogeneity for a boreal forest as characterized by continuous, fibre-optic DTS monitoring. Geoscientific Instrumentation, Methods and Data Systems 7, 223-234. [link] 

18) Kobayashi, H., Nagai, S., Kim, Y., Yang, W., Ikeda, K., Ikawa, H., Nagano, H., and Suzuki, R. (2018) In situ observations reveal how spectral reflectance responds to growing season phenology of an open evergreen forest in Alaska. Remote Sensing 10(7), 1071. [link]

17) Nagai, S., Akitsu, T., Saitoh, T.M., Busey, R.C., Fukuzawa, K., Honda, Y., Ichie, T., Ide, R., Ikawa, H., Iwasaki, A., Iwao, K., Kajiwara, K., Kang, S., Kim, Y., Khoon, K.L., Kononov, A.V., Kosugi, Y., Maeda, T., Mamiya, W., Matsuoka, M., Maximov, T.C., Menzel, A., Miura, T., Mizunuma, T., Morozumi, T., Motohka, T., Muraoka, H., Nagano, H., Nakai, T., Nakaji, T., Oguma, H., Ohta, T., Ono, K., Pungga, R.A.S., Petrov, R.E., Sakai, R., Schunk, C., Sekikawa, S., Shakhmatov, R., Son, Y., Sugimoto, A., Suzuki, R., Takagi, K., Takanashi, S., Tei, S., Tsuchida, S., Yamamoto, H., Yamasaki, E., Yamashita, M., Yoon, T.K., Yoshida, T., Yoshimura, M., Yoshitake, S., Wilkinson, M., Wingate, L., Nasahara, K.N. (2018) 8 million phenological and sky images from 29 ecosystems from the Arctic to the trpics: the Phenological Eyes Network. Ecological Research 33(6),  1091-1092. [link]

16) Ikawa, H., Chen, C.P., Sikma, M., Yoshimoto, M., Sakai, H., Tokida, T., Usui, Y., Nakamura, H., Ono, K., Maruyama, A., Watanabe, T., Kuwagata, T., and Hasegawa, T. (2018) Increasing canopy photosynthesis in rice can be achieved without a large increase in water use-a model based on free-air CO2 enrichment. Global Change Biology 24(3), 1321-1341. [link]

<Press Release by the National Agriculture and Food Research Organization, Japan>

<Introduced in INNOVATION NEWSNETWORK: Rice production under climate change>

<Summary> Improving the rate of photosynthesis is crucial for achieving higher crop yields. However, it is important to consider the potential increase in water usage required to support this productivity. Water use by plants is not only important for regional water resources but also for regulating the thermal environment, as evaporative cooling occurs on the leaf surface during water consumption. To investigate this issue, we conducted gas exchange measurements in a FACE experiment and developed a rice ecosystem model that we coupled with a 1-D atmospheric model. Our model simulations indicate that a high stomatal conductance of rice leaves can increase productivity while mitigating heat-induced damage to the grain, without a significant increase in water use.

15) Nagano, H., Ikawa, H., Nakai, T., Matsushima-Yashima, M., Kobayashi, H., Kim, Y., Suzuki, R. (2018) Extremely dry environment down-regulates nighttime respiration of a black spruce forest in Interior Alaska. Agricultural and Forest Meteorology 249, 297-309. [link]

14) Ikawa, H., Ono, K., Mano, M., Kobayashi, K., Takimoto, T., Kuwagata, T., & Miyata, A. (2017) Evapotranspiration in a rice paddy field over 13 crop years. Journal of Agricultural Meteorology 73, 109–118. [link]

<Summary> Eddy covariance has been performed in a rice paddy field for over a decade (Mase rice paddy site). We analyzed the data from the last 13 years, including the years with unique characteristics such as extremely high and low summer temperatures. Inter-annual variations of evapotranspiration were mostly explained by in situ meteorological factors except for years with anomalously poor growth and a high amount of rainfall. 

13) Yonemura, S., Ono, K., Ikawa, H., Kim, W., Mano, M., & Miyata, A. (2017)  Comparison of fallow season CO2 efflux from paddy soil estimated using laboratory incubation with eddy covariance-based flux. Journal of Agricultural Meteorology 73 (3), 140-145. [link]

12) Kobayashi, H. Yunus, A.P., Nagai, S., Sugiura, K., Kim, Y., Van-Dam, B., Nagano, H., Zona, D., Harazono, Y., Bret-Harte, M.S., Ichii, K., Ikawa, H., Iwata, H., Oechel, W.C., Ueyama, M., & Suzuki, R. (2016) Latitudinal gradient of spruce forest understory and tundra phenology in Alaska as observed from satellite and ground-based data. Remote Sensing of Environment 177, 160-170. [link]

11) Ueyama, M., Tahara, N., Iwata, H., Euskirchen, E., Ikawa, H., Kobayashi, H., Nagano, H., Nakai, T., & Harazono, Y. (2016) Optimization of a biochemical model with eddy covariance measurements in black spruce forests of Alaska for estimating CO2 fertilization effects. Agricultural and Forest Meteorology 222 98-111. [link]

10) Sueyoshi, T., Saito, K., Miyazaki, S., Mori, J., Ise, T., Arakida, H., Suzuki, R., Sato, A., Iijima, Y., Yabuki, H., Ikawa, H., Ohta, T., Kotani, A., Hajima, T., Sato, H., Yamazaki, T., Sugimoto, A. (2016) The GRENE-TEA model intercomparison project (GTMIP) Stage 1 forcing data set. Earth System Science Data 8 1-14. [link]

9) Ikawa, H., Nakai, T., Busey, R.C., Kim, Y., Kobayashi, H., Nagai, S., Ueyama, M., Saito, K., Nagano, H., Suzuki, R., & Hinzman, L. (2015) Understory CO2, sensible heat, and latent heat fluxes in a black spruce forest in interior Alaska. Agricultural and Forest Meteorology 214-215 80-90. [link]

 <Audio presentation narrated by Azusa Ikawa>

<Summary> An open black spruce forest is a highly dominant ecosystem in Interior Alaska. Measurements from eddy covariance reveal that the understory contributes significantly to CO2 flux, accounting for approximately half of the total amount. The understory explains most of the variability in energy fluxes. Our findings also suggest that the responses of NEE and latent heat flux to vapor pressure deficit differ significantly between the ecosystem and the understory, indicating that the latter may be more vulnerable to extremely warm or wet environments. The data used for this study was sourced from US-Prr (AmeriFlux).

8) Miyazaki, S., Saito, K., Mori, J., Yamazaki, T., Ise, T., Arakida, H., Hajima, T., Iijima, Y., Machiya, H., Sueyoshi, T., Yabuki, H., Burke, E.J., Hosaka, M., Ichii, K., Ikawa, H., Ito, A., Kotani, A., Matsuura, Y., Niwano, M., Nitta, T., O’ishi, R., Ohta, T., Park, H., Sasai, T., Sato, A., Sato, H., Sugimoto, A., Suzuki, R., Tanaka, K., Yamaguchi, S., Yoshimura, K. (2015) The GRENE-TEA model intercomparison project (GTMIP) overview and experiment protocol for Stage 1. Geoscientific Model Development 8 2841-2856.[link]

7) Ikawa, H. & Oechel, W.C. (2015) Temporal variations in air-sea CO2 exchange near large kelp beds near San Diego, California. Journal of Geophysical Research, Oceans 120 (1) 50-63. [link]

<Summary> Eddy covariance measurements collected over multiple years from a pier and boat-based measurements demonstrate that kelp forests near San Diego have significant potential as a CO2 sink. In addition, we present a flux measurement technique utilizing a motion-correction algorithm on a small boat.

6) Ikawa, H. & Oechel, W.C. (2014) Spatial and temporal variability of air-sea CO2 exchange of alongshore waters in summer near Barrow, Alaska. Estuarine, Coastal and Shelf Science 141 (20) 37-46. [link]

<Summary> Based on observations made by a boat-based pCO2 and a portable eddy covariance system, the CO2 flux along the coast of Barrow, Alaska exhibits significant heterogeneity. Specifically, this heterogeneity is characterized by a steady flow from the south along the shore (which acts as a sink for CO2), terrestrial runoff (which acts as a source of CO2), and landfast ice.

5) Ikawa, H., Faloona, I., Kochendorfer, J., Paw U, K.T. & Oechel, W.C. (2013) Air-sea exchange of CO2 at a Northern California coastal site along the California Current upwelling system. Biogeosciences 10, 4419-4432. [link]

<Summary> To study the air-sea CO2 flux in a coastal upwelling area, an eddy covariance tower was constructed at the intertidal zone of Bodega Marine Laboratory. The tower measured high CO2 efflux during periods of low sea surface temperature and high salinity. This finding was further supported by the buoy offshore, which showed a correlation between pCO2 and sea surface temperature and salinity. 

4) Ikawa, H. & Oechel, W.C. (2011) Air-sea CO2 exchange of beach and near-coastal waters of the Chukchi Sea near Barrow, Alaska. Continental Shelf Research 31 (13) 1357-1364. [link]

<Summary> We observed extremely low pCO2 on the shore of Barrow in early summer. This remarkably low pCO2 level is likely associated with the melting of landfast sea ice. The diurnal fluctuations in pCO2 indicate that biological processes may have also played a role in reducing pCO2 levels to such an extent.

3) Zona, D., Oechel, W.C., Richards, J.H., Hastings, S., Kopetz, I., Ikawa, H. & Oberbauer, S. (2011) Light-stress avoidance mechanisms in a Sphagnum-dominated wet coastal Arctic tundra ecosystem in Alaska. Ecology 92 633-644. [link]

2) Ikawa, H., Oue, H., Yoshimoto, M., Kobayashi, K. & Okada, M. (2005) Effect of FACE on rice leaf photosynthesis and transpiration in a paddy field - Changes of parameters in Farquhar and Ball-Berry models under elevated CO2. Journal of Agricultural Meteorology 60: 593-596. [link]

<Summary> As part of my master's thesis, I performed gas exchange measurements on rice leaves using a free air CO2 enrichment (FACE) experiment. Additionally, I developed models for photosynthesis and stomatal conductance and conducted a sensitivity analysis of the model parameters. The results indicate that the elevated CO2 condition led to a down-regulation of photosynthesis capacity and an up-regulation of transpiration capacity.

1) Oue, H, Tamoto, T., Ikawa, H. & Takase, K. (2005) Micrometeorological Model for Estimating Evapotranspiration from an Irrigated Maize Field in the Hetao Irrigation District in the Yellow River Basin. Journal of Agricultural Meteorology 60 537-540. [link]

Others

Hiroki Ikawa (2019) A literature review on vegetation-atmosphere interaction research for carbon cycle and energy balance in terrestrial ecosystems. Low Temperature Science (低温科学) 77 1-15. [link]

桑形恒男,  伊川浩樹, 丸山篤志, 小野圭介, 吉本真由美, 石田祐宣, 渡辺力( 2019) 水田群落微気象モデルの概要と農学分野への応用. 低温科学 77 125-136.

丸山篤志、伊川浩樹(2018)平成28年熊本地震により亀裂や不陸が生じた水田圃場の減水深の特徴. 九州沖縄農業センター研究資料95 10-17. 

斉藤和之, 森淳子, 町屋広和, 宮崎真, 伊勢武史, 末吉哲雄, 山崎剛, 飯島慈裕, 伊川浩樹, 市井和仁, 伊藤昭彦, 大石龍太, 太田岳史, 堅田元喜, 小谷亜由美, 佐々井祟博, 佐藤篤司, 佐藤永, 杉本敦子, 鈴木力英, 田中克典, 新田友子, 庭野匡思, Eleanor Burke, 山口悟, 2018: 北極陸域モデル相互比較GTMIPの熱・水収支解析. 雪氷, 80, 159-174. 

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