抄録
Freezing tolerance of plants is lowered by high temperatures in which plants are grown before exposure to subzero freezing temperatures. As a measure of freezing tolerance, we used the daily mean and/or the daily maximum air temperature, averaged over 10 days, before the daily minimum air temperature dropped below freezing point during early winter. For the vegetable crop, we assumed a freezing temperature of -3°C or -5°C. The 30-year temperature records from 15 AMeDAS observatories of the Japan Meteorological Agency were used. Of these, 13 are located in the Sanriku coastal region and two in the inland area of Iwate Prefecture. The calculated 10-day averages across the coastal sites were comparable to or larger than those of the inland sites. They showed a specific increase in the coastal zone ranging from Kuji to Yamada. The larger values resulted from relatively low minimum and high maximum temperatures, which are specific to that region. It is generally thought that coastal areas are suitable for the production of winter vegetable crops due to their moderate temperature regime. However, our results indicate that unlike the other typical coastal areas, the temperature regime of the Sanriku region is not moderate; therefore, it possibly increases the risk of crop freezing injury.
