The Possible Effects of Global Warming on Cropping Systems in China Ⅻ. The Possible Effects of Climate Warming on Geographical Shift in Safe Planting Area of Rice in Cold Areas and the Risk Analysis of Chilling Damage
【Objective】The period from 1961 to 2010 was divided into two stages, i.e., 1961-1980 and 1981-2010, combined with the scenarios of different temperature increases, then the geographical shift of rice safe planting areas in Heilongjiang province and the possible risk of chilling damage after the shift influenced by historical and future climate warming were quantitatively analyzed. 【Method】 Using the standard of the accumulated temperature zone and some agro-meteorological indicators, combined with ArcGis method, the geographical shift of accumulated temperature zones and northern limit for rice in cold planting areas were compared and analyzed. Using the risk assessment standard of chilling damage, the change characteristics of delayed chilling damage and sterile chilling damage in sensitive area of rice in cold areas were analyzed. The chilling damage characteristics in sensitive region under the background of climate warming and the risk evolution trends under the scenarios of different temperature increases were also evaluated.【Result】Compared with the results during the period from 1961 to 1980, the accumulated temperature zones moved northward and eastward obviously during 1981-2010, the average of which was northward 1.19°. The regions of maximum geographical shift were the fifth accumulated temperature zone and the sixth accumulated temperature zone. The region of maximum area increasing was the second accumulated temperature zone, which nearly covered Songnen Plain. The accumulated temperature zones under the future climate warming scenarios moved northward obviously. The region of maximum area increasing was the first accumulated temperature zone. Compared with the period 1961-1980, the average geographical shift of safe northern limit for rice in cold areas was northward 121 km and the maximum spatial displacement was in central part of Nenjiang- Wudalianchi- northern part of Xunke. The safe northern limit of rice in cold areas under the scenarios of 1-3℃ temperature increasing moved northward 410.5-545 km and the maximum spatial displacement was in northern part of Huma, Heilongjiang province. Rice could be planted in the whole region except Mohe under the scenarios of 3℃ temperature increasing. Compared rice sensitive planting region with nonsensitive region, the chilling damage risk in the sensitive region was obviously higher than nonsensitive region and the risk of sterile chilling damage was higher than delayed chilling damage. In rice safe planting areas of Heilongjiang province, the frequency of severe chilling damage was the highest, followed by light chilling damage, the frequency of moderate chilling damage was the lowest. The severe and light delayed chilling damage in the sensitive region during 1981-2010 showed an obvious increase. The risk of moderate delayed chilling damage in both sensitive region and nonsensitive region was low. The different grades of sterile chilling damage in sensitive region were higher than that in nonsensitive region. The different grades of chilling damage in sensitive region would be higher than that in nonsensitive region under future temperature increasing scenarios.【Conclusion】Under the background of climate warming as well as scenarios of different temperature increases, the accumulated temperature zones and safe northern limit of rice in cold areas had shown an obvious northward moving. The risk of chilling damage in sensitive region was obviously higher than that in nonsensitive region. The risk of chilling damage would be decreased as temperature increasing, but the defensive measures in sensitive region should be strengthened, such as adopting improved cultivation techniques, planting early-maturing varieties, as well as avoiding blind area and varieties expansion in rice planting areas.