| The Huang-Huai-Hai Plain(3H Plain)is a major crop producing area in China,providing about 70% of national wheat production with a dominant winter wheat-summer maize double cropping system.However,due to the maldistribution of precipitation,water scarcity has been the limiting factor for wheat production in 3H Plain.Furthermore,the 3H Plain has been concluded as the sensitive and vulnerable area to climate change.Water limitation is likely to be accentuated by warming temperature and increasing variability of precipitation,along with increased food demand,soil quality deterioration and overexploitation of groundwater resources.Thus,understanding the potential impact of climate change,especially drought impact,is essential for reducing vulnerability and establishing adaptation strategies for agricultural products in 3H Plain.Here,the winter wheat phenology and yield for baseline(1976-2005),short-term(2010-2039),medium-term(2040-2069)and long-term(2070-2099)was simulated by CERES-Wheat model coupling with the RCP 8.5 climate projection from Had GEM2-ES climate model to investigate the possible impact of future climate.And the contributions of changes in temperature,solar radiation,precipitation and CO2 concentration in isolation were also compared for different future periods.Then,by comparing the correlation coefficients between recorded agricultural drought area and drought indices,drought index with higher applicability was selected to analyze the future drought conditions in a climatic perspective.At last,the potential impact of future drought on winter wheat yield was simulated,and the compensation ability to drought impact for different irrigation adaptation strategies was further evaluated.The results can be concluded as follows:(1)Compared to baseline period,the maximum temperature during winter wheat growing seasons will be 0.55,2.17 and 3.86? higher for the short-term,medium-term and long-term;the minimum temperature will also increase by 0.31,1.62 and 3.56? for the three periods of RCP8.5 scenario.The seasonal received solar radiation is 1.69%,4.24% and 2.36% higher in the three periods compared to baseline,and the seasonal precipitation also shows 16.73%,28.64% and 50.09% higher for the three periods,respectively.Due to the warming temperature,growth duration from sowing to harvest during the short-term,medium-term and long-term will be shortened by 4,15 and 25 days respectively,while the growth duration between sowing and anthesis will be shortened by 4,15 and 24 days respectively.Thus,future warming will not affect the growing period between anthesis and maturity,during which is important for grain filling.(2)Climate change under RCP8.5 scenario would be beneficial to wheat production.When the fertilizer efficiency of CO2 is out of consideration,winter wheat yield would be increased by 13.14%,14.88% and 29.10% for the mentioned three periods.And the relative contribution ratio between warming temperature,increasing solar radiation and precipitation is-0.3:0.4:0.9 for short-term,-0.4:0.3:1.1 for medium-term,and-0.2:0.2:1.0 for long-term.Specifically,the increasing precipitation would elevate yield by 11.74%,16.38% and 27.78% for the three period respectively.The impact of increasing precipitation in isolation is recognized as the dominant factor to climate change impact.However,the impact of warming temperature on wheat yield is more complicated,with the spatial distribution of positive impact in south and negative impact in north of 3H Plain.Overall,warming temperature would cause wheat yield to decrease by 3.64%,5.87% and 5.81% for different future period.Further analysis demonstrated that the potential evapotranspiration would increase with warming temperature and consequently aggravate water shortage in north.However,in the south part of 3H Plain,although the potential evapotranspiration would be enlarged in warming conditions,the rich precipitation can offset the higher demand of evapotranspiration.Thus the impact of warming temperature on wheat yield shows difference between south and north.Similarly,although increasing solar radiation positively affect wheat yield by 5.04%,4.37% and 7.14%,it also increased the potential evapotranspiration.Thus,for 3H Plain,water shortage is the limiting factor for winter wheat to take fully advantages of increasing heat and radiation resources.The fertilizer efficiency of CO2 was also assessed.With the increasing concentration of CO2 from 380 ppm at baseline period,to 423,571 and 798 ppm for three future periods,the increasing CO2 concentration would elevate wheat yield by 3.68%,17.74% and 41.87% for the three future period.(3)Correlation analysis between reported agricultural drought area and drought indices(including the Standardized Precipitation Index [SPI],the Standardized Precipitation Evapotranspiration Index based on the Penman–Monteith equation [SPEI-PM],and the Thornthwaite equation [SPEI-TH])demonstrated that SPEI-PM is more suitable for drought analysis in the 3H Plain.Under the RCP8.5 scenario,although precipitation will keep rising at the rate of 1.88mm·yr-1,the potential evapotranspiration will be enlarged in a higher rate(3.58 mm·yr-1).Thus,drought characteristics analysis based on SPEI-PM demonstrated that drought risks in the 3H Plain will be intensified in the future in climatic perspective with higher frequency,longer duration,and worse severity.(4)With more serious climatic drought conditions,the potential drought impact on yield(yield gap between potential yield and rainfed yield)is predicted to be increasing.The potential yield reduction rate cause by drought is 41.58%,47.31%,53.54% and 50.92% for baseline,the short-term,mediumterm and long-term.The compensation ability of jointing water for the future three period are 16.30%,18.67% and 16.66%,which is the highest compared to winter water and anthesis water.The compensation ability of jointing water and anthesis water can reach 23.64%,25.17% and 23.77%,which is almost half of the potential yield reduction rate.Thus,in the 3H Plain,especially for the north part of the plain which is facing limited water resources,first priority should be ensuring the jointing water.For regions permits more irrigation,jointing water and anthesis water can offset almost half of the negative impact caused by drought.Additionally,although the simulated yield compensation ability for winter water is the lowest,but in the real agricultural conditions,winter water is one of the key factor to maintain high and stable yield as it determines the seedling conditions and safety overwintering.Thus,for the north part of 3H Plain which has suffered from serious droughts with lower winter temperature,besides jointing water and anthesis water,winter water should also be important to guarantee the safety of wintering period,especially for cold winter conditions. |
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