Model Simulation of Global Climatic Change Effects on Regional Rice Production

In order to describe the effects of [CO2], temperature and other environmental factors on rice growth and yield formation processes, several models have been developed for simulating global climate change effects on rice to predict these effects at a given location and to develop strategies for production technologies adapted to climate change. These models include SIMRIW (Horie, 1993; Horie et al., 1995a), CERES-RICE (Singh and Paddila, 1995) and ORYZA1 (Kropff et al., 1995). Figure 5.10 summarizes the yield responses of a japonica-type rice to various air temperatures, solar radiation and [CO2] as simulated by SIMRIW (Horie et al., 1995a). This model adequately simulated observed year-to-year variations in rice yield for many locations in Japan (Horie, 1993) as well as the seasonal variation in rice yields at Los Baños, the Philippines (Horie et al., 1995a). However, these simulations were based on current climates. Further improvements to existing rice models are needed to account for the interactive effects of [CO2], temperature and N on rice growth and the yield formation processes described in the previous sections of this chapter.

Despite these limitations, work with both SIMRIW (Horie et al., 1995b, 1997a) and ORYZA1 (Matthews et al., 1995, 1997) has pointed out important implications of potential climate change on future rice yields in Asia. These simulations utilized climate scenarios from three global circulation models: GISS (Goddard Institute for Space Studies), GFDL (Geophysical Fluid Dynamics Laboratory) and UKMO (United Kingdom Meteorological Office). These simulations indicate that future climate change may result in substantially increased irrigated rice yields for the northern parts of China, Korea and Japan, and areas in tropical Indonesia and Malaysia. However, for southern Japan, as well as inland areas in subtropical Asia, reductions in rice yields are possible due to high-temperature-induced spikelet sterility and shortening of crop growth durations. These simulations also indicate that

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Air temperature (°C)

Fig. 5.10. Simulated yield of rice (cv. Nipponbare) at different daily mean temperatures, solar radiation and [CO2] under constant environmental conditions. Daylength and diurnal temperature range were set at 12 h and 8°C, respectively. (Adapted from Horie et al., 1995a.)

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Air temperature (°C)

Fig. 5.10. Simulated yield of rice (cv. Nipponbare) at different daily mean temperatures, solar radiation and [CO2] under constant environmental conditions. Daylength and diurnal temperature range were set at 12 h and 8°C, respectively. (Adapted from Horie et al., 1995a.)

mitigation of the negative effects of climate change by altering planting dates in southern Japan, in order to avoid damagingly high temperatures, proved unsatisfactory because rice growth in the cooler season was limited by lower solar radiation due to the season of the year.

Rice models developed so far are relevant only to irrigated rice. Since rainfed rice cultures are considered more vulnerable to anticipated global climate change, synthesis of a reliable model for simulating growth and yield of rainfed rice is needed.

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