Spatio-temporal Variation Of Rice Chilling Damage In Northeast China Under Climate Change

Based on the daily mean temperature and monthly mean temperature in the 89 meteorological stations in Northeast China from 1978 to 2012,which are interpolated in 0.02 degree grid,thespatio-temporal variations of annual mean temperature,monthly mean temperature in growing season were analyzed.Then based on the rice yield data from 1978 to2012,the temporal variations of rice yield were analyzed.Pearson correlation analysis method was adopted in the analysis of correlation bewtweenthe monthly mean temperature summation anomaly in the growing season with rice yield.Based on the related indicators,the temporal variation and spatial frequency distribution of rice delayed chilling damage and rice obstacle chilling damage were studied.The main results are as follows:(1)The overall trend in the three provinces in Northeast China of the annual mean temperature and the monthly mean temperature summation in the growing season are increasing,the monthly mean temperature summation in the growing season are more significant than the annual average temperature.The increasing trend of the temperature in Liaoning Province is weaker than that in Heilongjiang Province and Jilin Province.The monthly mean temperature summation anomaly in the growing season in the three provinces show an obvious upward trend,mainly negative anomaly before 1996,and positive anomaly after 1996.The boundary of annual mean temperature and monthly mean temperature summation in the growing season moved northward obviously.The growth trend of unit yield of rice in three provinces in northeast China is that Heilongjiang Province is stronger than Jilin Province is greater than Liaoning Province,and the fluctuation of unit yield of rice in Jilin Province is greater.The change of unit yield of rice was significantly correlated with the change of monthly mean temperature summation anomaly in the growing season from 1978 to 2012.Heilongjiang Province had the strongest correlation(0.678),Jilin Province had the weakest correlation(0.453),and the correlation of Liaoning Province is 0.543.(2)The value of RCDG(standing for Ratio of Chilling Damage Grids,defined as the ratio of the number of chilling damage occurrence grid points to the total number of chilling damage grid points in each province annually)of delayed chilling damage in three provinces in northeast China decreased with time from 1978 to 2012.From the beginning of the 21 st century,the RCDG value of delayed chilling damage in Liaoning Province and Jilin Province was lower than the mean value of RCDG in 35 years.The RCDG value of three grades of chilling damage in Heilongjiang Province in 2002 and 2009 exceeded the average value of 35 years.The mean RCDG of severe chilling damage was higher than that of mild chillingdamage and moderate chilling damage.The RCDG values of severe chilling damage in Heilongjiang,Jilin and Liaoning were 0.24,0.21and0.13 respectively.The mean values of mild chilling damage and moderate chilling damage in the three provinces were below 0.1.From 1978 to 2012,the frequency of severe delayed chilling damage was significantly higher than that of moderate and mild chilling damage.The distribution of severe chilling damage is mainly concentrated in Heilongjiang Province,the eastern part of Jilin and Liaoning Province.Mild chilling damage occurs more in Heilongjiang Province,moderate chilling damage occurs more in the western part of Jilin Province.The three grades of delayed chilling damage showed that the occurrence area in the 1980 s was bigger than that in the 1990 s and bigger than that in the 1990 s.(3)During 1978-2012,the RCDG of three grades of obstacle chilling damage at booting stage in Heilongjiang Province and Jilin Province were lower in the 1990 s,and there were almost no obstacle chilling damage at booting stage in Liaoning Province in 35 years.In Heilongjiang Province,during 1978-2012,the maximum RCDG value of mild chilling damage at heading stage occurred in the 1990 s,while the RCDG value of moderate and severe chilling damage was lower in the 1990 s.In Jilin Province,the value of mild and moderate chilling damage at heading stage was the highest in the 2000 s,and the severe chilling damage decreased with the age.The chilling damage at heading stage in Liaoning Province was lower in the 1990 s,the maximum RCDG value of mild chilling damage was in the 2000 s,the maximum RCDG value of moderate and severe chilling damage was in the 1980 s.From 1978 to 2012,the occurrence frequency of severe chilling damage of obstacle chilling damage at booting stage was less than that of mild and moderate chilling damage,and the higher frequency was mainly concentrated in Heilongjiang Province,and the eastern part of Liaoning Province and Jilin Province.The maximum frequency of chilling damage of obstacle damage at heading stage was smaller than that at booting stage,but the area of chilling damage of obstacle damage at heading stage was larger than that at booting stage.Obstacle chilling damage generally occurred in a smaller range in the 1990 s.