Responses Of Crop Growth To Climate Change In Northwest China

In this paper,from 743 gauging stations across the nation,which are available at the National Climate Center,a total of 166 stations in Shaanxi,Gansu,Qinghai,Xinjiang and Ningxia Hui Autonomous Region 5 provinces(autonomous regions) that own effective data series for 40 years and more are selected.By using the percentile mothed,definition the threshold value of the extreme precipitation and temperature on the northwest china,and calculation the precipitation,extreme precipitation intensity,frequency,effective days of extreme maximum(minimum) temperature in different seasons and years in Northwest china. At the same time,from the crop growth information of agro-meteorological gauging stations across the northwest china,a data set of cotton,corn spring,summer corn,winter wheat and spring wheat of 40 stations that own effective data series for 20 years and more are selected, and the variation characteristics were analyzed by using Mathematical statistics.The results showed that:(1) In the past 54 years in northwest China 5 provinces(autonomous regions) the total precipitation was reducing,extreme precipitation was no significant change in trend,but showed some characteristics of stage changes,the frequency of extreme precipitation increased intensity,and extreme precipitation show weakly rise trend.(2) In the past 54 years in northwest China,the change of high temperature days which temperature greater than or equal to 35℃was not obvious,days which temperature greater than or equal to 30℃increased,the number of days which temperature equivalent and less than 0℃in the rapid decline,the number of low temperature days which temperature less than or equal to -20℃show smaller reduce trend;days of low temperature which temperature less than and equal to -30℃unchanged;days of extreme maximum temperatures appear to increase;days of extreme minimum temperature on a decreasing trend.(3) In Northwest over the past 20 years,the average cotton sowing period in varying degrees in advance,most of the cotton stop growth period were postponed,and the growth period were extended.(4) In Northwest China,spring wheat sowing period did not show consistency change postponed in the most areas of Qinghai,Xinjiang and advanced in the most areas of Gansu, Ningxia and Xinjiang.Spring wheat maturity period advanced consistency,and change of growing period has not shown consistency.(5) Over the past 20 years in most parts in northwest,the winter wheat sowing date in the postponement,the winter wheat turning green period has not shown the consistency and maturity period are expressed in advance.In northwest,turning green - mature period reduced of winter wheat in most areas,but increased in some other areas.(6) The sowing date of spring maize in advance in Gansu in the past 20 years,and no change in Xinjiang.The maturity period in advanced in varying degrees,but the trend were not clear.(7) Shaanxi's summer maize sowing date postponed while advanced in Xinjiang.Sowing in advance provided more energy and fertility for the latter part growing conditions,and increased the yield of summer corn.(8) In Gansu and Shaanxi,the extreme earlier sowing period of cotton mainly appeared after 1996,while the extreme latest owing period mostly before 1996.The extreme sowing period of cotton relatively even distribution in the 5 stations of Xinjiang.In Gansu,the extreme earlier stop-growth period of cotton mainly appeared before 1998 while the extreme latest stop-growth period mainly after 2000.In Shaanxi,the extreme earlier stop-growth period of cotton mainly appeared before 1998 while the extreme latest stop-growth period distributed more evenly,and the extreme longest growth period mostly appeared in 2000s.In Xinjiang,the extreme earlier stop-growth period of cotton often occurred after the year of 2000 while the extreme latest stop-growth period mostly after the mid-1990s,and most of the extreme shortest growth period before the mid-1990s while the extreme longest growth period after the mid-1990s.