Responses And Adaptations And Their Regional Differences Of Winter Wheat Productivity To Climatic Warming

The global mean air temperature has increased0.74℃in the past100years and is projected to rise about1.8-4.0℃in the next100years. In China, relevant forecast reports that the mean air temperature will increase2.3-3.3℃and the temperature during winter wheat growth season which includes winter and spring will significantly rise. Temperature is one of the most important factors on the growth of wheat. To address the response of climate warming on winter wheat production and make long-term food security strategy decision, it is great significance to study the responses of wheat production to the climate warming. So far, these researches were mostly based on the model projection and historical data analysis, and parts of experiments also were conducted under artificial controlled conditions. These results were difficult to understand real and comprehensive effects of actual warming on winter wheat in the field. Therefore, the main winter wheat production areas in China as the research object, winter wheat response and adaptation to climate warming and regional difference were systematically investigated using historical data mining, and field warming trials combined in main region of winter wheat in China. In this paper, characteristics of climate change, yield variation and its relationship with climate change were analyzed, and the actual response and adaptation characteristics of winter wheat growth to climate warming, and its biological mechanism was ascertained. It will provide theoretical and technical support for winter wheat variety improvement and adjustment of plant area under climate warming. Main results in this paper are as follows:(1) In1989-2009, daily mean temperature, daily maximum and minimum temperature of winter wheat growing season had significantly increased by0.67,0.55and0.52℃decade-1during winter wheat growing season in the study area, and there were differences in different areas. According to theoretical calculations using the accumulated temperature method, date of sowing was delayed by0.8d decade-1. However, the date of anthesis and maturity were advanced by4.1and5.1d decade-1during1989-2009, respectively (P 0.01). The light-temperature potential productivity of winter wheat was enhanced by71.7kg ha-1year-1in the study area from1989to2009, and there was an advance trend of increase from the east to the west. In the northwest of study area, increase of the light-temperature potential productivity was the highest (150kg ha-1year-1).(2) Based on agricultural statistical and meteorological data from1989to2009at prefecture-level cities, the relationships among actual yield trend, de-trend yield trend using a3-year moving average method, de-trend yield trend using quadratic regression method at prefecture-level cities and main climate factors anomal were analyzed. The results indicated that winter wheat yield changed by climate warming, and responses of yield to different meteorological factors were not similar. Specifically, the relationship between daily minimum temperature and yield trend was the highest, and there were regional differences. According to a regression analysis of the anomalies of actual yield trend, de-trend yield trend using a3-year moving average method and de-trend yield trend using quadratic regression method at prefecture-level cities prefecture-level cities, a1.0℃increase in daily minimum temperature would lead to an increment of538.0,21.7and33.5kg ha-1year-1in the study area, respectively. Meanwhile, the similar result was found by analysis of relationship between yields of16mid-long term experiment sites and meteorological factors.(3) Averaged on three years, nighttime warming advanced the anthesis and maturity by3,5,6,7d and1,2,1,2d at Zhengjian, Henan, Xuzhou and Shijiazhuang sites, respectively, but prolonged the length of post-flowing stage by2,3,5and5d. Meanwhile, the aboveground biomass and grain yield at Zhengjian, Henan, Xuzhou and Shijiazhuang sites were significantly higher by20.8,19.6,12.3,18.5%and8.9,13.9,11.8,11.7%in the nighttime warming plots than in the control, respectively. By analyzing the yield components, the results indicated that yield increase was mainly due to higher1000-grain weight and grain number per spike in the nighttime warming plots than in the control. Warming enhanced1000-grain weight by4.7,6.0,6.7and7.1%(P<0.05) compared with control treatments at Zhengjian, Henan, Xuzhou and Shijiazhuang sites, respectively. Meanwhile, negative regressions between background temperatures of site, and variations of length of growing period and productive were found under nighttime warming condition. The lower the background temperature, the greater the variations of length of growing period, and productive to nighttime warming.(4) Compared to control treatments, nighttime warming significantly increased flag area and total green area by38.3and12.6%, respectively. Flag leaf photosynthesis and nighttime respiration rates were higher in the nighttime warming plots than in the control plots by2.8and0.6umol CO2m-2s-1, respectively. Meanwhile, depletion of soluble sugar and starch for top three leaves were increased by nighttime warming at nighttime, but it was higher accumulation at daytime than depletion at nighttime. These results implied that the stimulations of nighttime respiration and carbohydrate depletion could be overcompensated by nighttime warming led to the photosynthetic compensation mechanism.(5) Under nighttime warming condition, responses of total starch and amylose content in grains of winter wheat to nighttime warming were similar at each site. Averaged on two growing seasons of2007-2008and2008-2009, the nighttime warming plot resulted in5.6and9.3%lower total starch and amylose, respectivly at Zhengjian, and1.4and23.4%at Henan than that of control plot. On the contrary, these were higher by7.7and9.3%, respectively at Xuzhou, and by6.4and9.3%at Shijiazhuang. Nighttime warming declined protein contents in the winter wheat grain, but increased protein yield per unit area. Averaged on two growing seasons of2007-2008and2008-2009, protein content was lower by0.7,0.7,8.4and7.6%in the nighttime warming plots than in the control plot at Zhengjian, Henan, Xuzhou and Shijiazhuang sites respectively, and protein yield per unit area was higher by10.3,4.7,1.5and5.5%.(6) Nearly60years, the growth period and vernalization process of breeding new winter wheat varieties were shortened and cold resistance of varieties became week. For Northern winter wheat area, length of breeding varieties period shortened by1.00d decade-1and the proportion of winterness varieties declined, the proportion of weak winterness varieties increased. In case of Huang-Huai winter wheat area, length of breeding varieties period basically remained stable and the proportion of winterness and weak springness varieties became fewer and fewer, but the proportion of weak winterness and weak springness varieties became more and more. For Yangtze River winter wheat area, length of breeding varieties period shortened by0.41d decade-1and the proportion of springness varieties reduced, the proportion of weak winterness and weak springness varieties enhanced. In addition, length of sowing to anthesis and whole period shortened by0.66and0.42d decade-1, but length of anthesis to maturity increased by0.28d decade-1according to field observation in the whole study area from1992to2009. Meanwhile, during growing stage negative regressions were found among the length of sowing to anthesis and maturity, and temperature. There were negative regressions among the length of anthesis to maturity, and daily average temperature and maximum temperature, but there were positive regressions between the length of anthesis to maturity and daily minimum temperature. Compared with1990s, shortage length of sowing to maturity trended to increase from east to west in2000s.