Assessment of paddy rice heading date under projected climate change conditions for Hokkaido region based on the field experiment

Abstract

Impact assessment and adaptation planning to enable growth of paddy rice (Oryza sativa L.) under conditions of ongoing climate change are necessary in the Hokkaido region of northern Japan because of the intensive climate warming ( 2-3 in summer) projected to occur during the 21st century. Most previous studies have been based on extrapolation of results from past and present experimental data on unexperienced warming conditions under projected climatic change. These facts motivated us to use an assessment method known as an open-field day-length-extension (ODE) experiment. First, we confirmed the feasibility of an ODE experiment, which involves artificially extending day length with supplemental lighting. ODE treatment was performed in Morioka in 2009 (treatment ODE09M), where the summer temperature was 2.5 higher than the current average summer temperature in Sapporo, and the results were compared with those obtained in Sapporo, Hokkaido, in 2010 (treatment C10S), which had an extraordinarily hot summer (mean daily temperature 2.3 higher than normal). The difference in heading date between ODE09M and C10S was small, i.e., 4 days for the three cultivars Koshihikari, Hitomebore, and Akitakomachi. Second, by comparing previous temperature gradient chamber (TGC) results with those from the ODE experiment, we found that a TGC experiment system was likely to overestimate the effect of temperature on heading date by up to 7 days. Finally, we calculated paddy rice cultivation under projected climate change conditions in Sapporo in terms of three critical dates for stable rice cultivation: the early limit for transplanting, the early limit for heading, and the late limit for heading. The warmer climate condition at Morioka formed by the ODE experiment that is an analog of future climate (2.5 higher than the current average) at an northern site, Sapporo, would allow successful cultivation of Hitomebore and Akitakomachi, but not Koshihikari, in Sapporo.

Probabilistic Risk Assessment of the Rice Cropping Schedule for Central Hokkaido, Japan

“…6). This result is consistent with the results of open-field experiments designed to assess the effects of warmer conditions than present (Nemoto et al 2011a).…”

“…Our results indicated that heat risks not currently existing will occur in Hokkaido under the highest projections of climatic warming (14.78C). In fact, rice yield in Hokkaido decreased in 2010 owing to abnormally high temperatures (12.28C), especially from the end of June to early July, which shortened the vegetative growth period and reduced the number of tillers and number of grains per plant (Nemoto et al 2011b). This was the first time a reduction in rice yield caused by hot conditions had been recorded in Hokkaido.…”

“…Kirara 397, Akitakomachi, and Hitomebore have nearly identical values of R-CPI, around 6.0 Mg ha 21 . Nemoto et al (2011b) reported that Hitomebore fully ripened and produced a yield of 6.3 Mg ha 21 in an extremely hot year (2.28C higher than normal) in 2010 in Hokkaido. However, it is still difficult to cultivate Koshihikari because the probability of a loss occurring from one of the risk factors is high for any transplanting date (Fig.…”

“…2): Sapporo in Hokkaido (northern Japan), Morioka in the Tohoku region (northeast Japan), Tsukuba in the Kanto region (mid Japan), and Kumamoto in Kyushu (southern Japan). The cooperative experiments were conducted at the four sites during 2 yr (2009 and 2010) using an open-field day-length-extension experiment (ODE experiment) Nemoto et al 2011a), which provided pseudo-global warming conditions with lightbulb irradiation. The experimental data did not include the effects of CO 2 enrichment.…”

Adaptation of rice to climate change through a cultivar-based simulation: a possible cultivar shift in eastern Japan

“…Thus, introducing the 'southern cultivars' would be an effective way to adapt to the future climate in approximately 36% of the study area. An observational study also suggested the introduction of a southern cultivar to mitigate the hightemperature damage projected for the current leading cultivars (Nemoto et al 2011).…”