The Influences Of Climate Change On Yield Fluctuation Of Winter Wheat And Its Evolution Trend In China

Droughts and water shortage are generally accepted to be one of the most critical problems faced by worldwide agriculture,and it is so especially in China where agricultural production and prosperity are largely dependent on the timely,adequate and proper distribution of rainfall.In the past 30 years,winter wheat yield in China has been experiencing a sustained growth.The change of driving factors,such as climate change,technology and policy,totally contribute to the yield increase.Untangling relative contributions of recent climate,variety and fertilizer change to wheat yield,and understanding the sensitivity and impact on wheat yield for various climate variables is essential for dealing with climate-crop relationship and agricultural-climate adaptation.In the thesis,four main winter wheat growing region(i.e.HuangHuai wheat region-HH,the middle and lower reaches of Changjiang River wheat region-CJ,southest wheat region SW and northwest wheat region-NW)categorized by the Ministry of Agriculture and Rural Affairs and ecological types of winter wheat has been taken as the research unit,in which the relative contributions of climate change,variety renewal and increasing fertilizer to winter wheat yield during 1980-2010 were untangled,and the relative impact of changes in temperature,solar radiation and precipitation on rainfed winter wheat yield in isolation were additionally analyzed.The main conclusions were summarized as the follows:(1).The contribution of climate change was more complex than variety renewal and fertilizer increase,varied between decades.Compared to the 1980s,climate change in the 1990s was dominated by positive effect,resulting in 2.6%,3.1%and 1.0%of yield increase in HH,CJ and NW,with the negative contribution only in SW,in which wheat yield declined by 1.5%.However,the contribution of climate change in the 2000s turned to be negative,which declined yield by 0.7%,11.5%and 2.8%in HH,CJ and SW,with the positive contribution only in NW of which the yield increased by 3.4%.(2).Compared to climate change,variety renewal and fertilizer increase were the main driving factors to winter wheat yield increase during the 1981-2010.In the HH,the contribution rates of variety renewal and fertilizer increase almost equals,rising the yield by 15.47%and 13.13%,respectively.In the CJ and NW,the contribution rates of variety renewal was the highest one.The yield was increased by 31.7%and 25.8%because of variety renewal for these two wheat regions in 2000s.In the SW,variety renewal was governed factor that affect wheat yield in the 1990s.However,it turned to be fertilizer increase that mostly impact wheat yield in SW during the 2000s.(3).The sensitivity analyze of climate variables to rainfed yield showed that the effect of temperature varied between different regions.Each 1?increase in growing season temperature could linked to a 2.2%and 1.5%yield decrease in HH and NW,while was likely to improve yield by 9.63%and 1.4%in CJ and SW.However,the sensitivity of solar radiation and precipitation were all positive to each region.Each 1 MJ/m~2(or 1mm)increase in solar radiation(or precipitation)could linked to0.01%—0.02%(or 0.12%—0.46%)yield increase for different wheat regions.(4).In the perspective of the cumulative impact of each climate variable during 1980-2010,the dominated climate variable that affect rainfed yield mostly was various between different wheat regions.In the HH,both temperature and solar radiation were detected to be governed variables.During the1981-2010,1.0?warming of temperature and 99.3 MJ/m~2 decrease of solar radiation has reduced rainfed yield by 2.2%and 2.4%,respectively,while the impact of precipitation is insignificant due to the little change amplitude.In the CJ,0.8?of warming temperature and 51.2 mm increase of precipitation has improved yield by 7.8%and 6.2%,respectively,both of which were the dominate climate variables.In the SW,warming temperature(0.9?)and increasing solar radiation(57.7 MJ/m~2)has increased yield by 1.2%and 1.2%respectively,while the decreasing precipitation(14.8 mm)has declined yield by 1.8%.Furthermore,the NW has experienced an increase of 104.1 MJ/m~2 for solar raduation and a decrease of 27.6 mm for precipitation,which linked to a 1.4%of yield increase and3.2%of yield decrease,respectively.