Abstract: To reduce the impact of chilling damage, an experiment of sowing and transplanting by stages of middle-late rice variety of Jijing 811 was conducted in Yanji, eastern Jilin Province in 2013 and 2014. The response of growth rate and yield of roundgrained rice to transplanting and temperature change was analyzed, and the suitable sowing/transplanting dates of the rice were defined. The results showed that, with the delay of sowing/transplanting date, the average air temperature during the rice growth period rose, the rice growth was accelerated, and the effective growing days decreased. During the main growing periods of rice, when the mean temperature rose by 1 ℃, the growth rate increased by 19%, and growing days decreased approximately 5 days. The suitable daily mean temperature for rice transplanting was about 13.0 ℃, and there was a reduction in rice yield when transplanting was earlier or later. To ensure rice maturation before the frost and get high yield, middlelate variety rice should be sowed on about April 18, and transplanted on about May 26 in the study area. For the middle-late maturing rice varieties, suitable accumulated temperature during transplanting to mature period was 2280 ℃·d or so. If the accumulated temperature decreased by 100 ℃·d, rice yield would decrease by 1095 kg·hm^-2 (about 13%). Insufficient accumulated temperature may induce the occurrence of rice chilling injury, and thus a reduction of rice yield.

Key words: ecological risk assessment, heavy metal in surface sediments, Yalu River estuary wetland, spatial distribution