Effects Of Increased Precipitation And Nighttime Warming On Winter Wheat Yield In North China Plain

As the concentration of atmospheric greenhouse gases keeps rising,climate warming is becoming more and more obvious.Average global surface temperatures are expected to rise by 1.0-3.7 °C by the end of the century.Previous studies have revealed that the global nighttime minimum temperature is rising more quickly than the daytime maximum temperature,and agricultural production shows a higher sensitivity to the increased nighttime minimum temperature.Concurrent with global warming,changing precipitation has also been observed over the world.In the future,precipitation will increase in North China Plain,which will have an important impact on crop production in drylands.As global climate change intensifies,increasing attention has been paid on the impacts of climate factors on the growth and production of global crops.The North China Plain is an important food production base in China,which is of great significance for ensuring national food security and sustainable social development.However,it is still unclear how climate warming and changing precipitation affect the production of wheat in the North China Plain as well as whether there is an interaction between the effects of temperature and precipitation on crop growth.As an important food crop in the region,wheat 's response to climate change is particularly critical for food security.There is a lack of direct field experiment data in this regard.Therefore,a manipulative experiment including control,nighttime warming,increased 30% precipitation and nighttime warming plus increased 30% precipitation was conducted in Farms of Henan University since 2016 to explore the responses of biomass and yield of winter wheat to future nighttime warming and increased precipitation.From 2016 to 2018,neither nighttime warming nor increased precipitation affected soil p H,ammonium nitrogen,nitrate nitrogen and available nitrogen,respectively.Nighttime warming significantly increased the soil temperature at night by 0.86 °C,but showed no effect on soil moisture.Increased precipitation had no influence on soil temperature at night,but increased soil moisture by 1.73 V/V%.There were no interactions between the effects of nighttime warming and increased precipitation on the above parameters.In 2016,nighttime warming shortened the jointing period of wheat by 1.00 day,the filling period by 2.00 days,and the entire growing season by 4.50 days,respectively,but had no effect on heading and flowering periods.Increased precipitation showed no effect on all stages of wheat growth,but extended the entire growing season by 1.50 days.There was no interaction between the effects of nighttime warming and increased precipitation on wheat phenology.Across the 3 years(2016-2018),nighttime warming marginally reduced the aboveground biomass of wheat by 9.63% and total biomass by 9.28%,respectively.Increased precipitation enhanced aboveground biomass and total biomass by 14.91% and 13.80%,respectively.Both the aboveground and total biomass of wheat were negatively correlated with nighttime soil temperature,but positively correlated with soil moisture.In addition,nighttime warming significantly reduced the number of wheat grains per spike by 10.18%,and thus decreased the grain yield of by 13.51%.Increased precipitation significantly increased the grain number and grain weight of per spike,and the grain harvest index of wheat by 22.62%,20.03% and 0.03(absolute change),respectively,and thus enhanced the grain yield of wheat by 22.66%.The number of grains per spike decreased with the increasing nighttime soil temperature,but increased with enhancing soil moisture and total biomass.The grain weight enhanced with the increasing soil moisture and total biomass.Stepwise multiple regression analyses showed that the number of grains per spike and grains weight accounted for 69% of the change in yield.In this study,nighttime warming decreased wheat yield primarily by reducing the number of wheat grains.However,elevated wheat yield under increased precipitation resulted from increased number of grains,grain weight,wheat biomass and harvest index.The mechanisms of nighttime warming and increased precipitation on wheat yield are different.Therefore,our findings of reduced wheat yield under nighttime warming and increased wheat yield under increased precipitation will provide reliable data and further theoretical support for decision-making to ensure stable and high yields of crops in the North China Plain under climate warming and increased precipitation.