Effects of climate change on winter wheat yield in low/high yield years in Ningjin County,Hebei Province
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Abstract:
Wheat is one of the main grain crops in China,and in 2019,China′s wheat production reached 133.6 million tons,accounting for 20% of total grain production.Climate change,especially the extreme climate,does a significant impact on winter wheat yield.Identifying the main influencing factors could help farmers to choose appropriate methods to alleviate the risk to wheat production.For different regions,the impact of climate change on winter wheat cultivation varies.Hebei Province is one of the main wheat-producing areas in China,and Ningjin County is the largest wheat-producing county in the plain area of Hebei.Therefore,it is important to analyze and identify the main climatic factors affecting wheat yield in the region and propose corresponding countermeasures to guide local agricultural production and guarantee high and stable crop yields. Mann-Kendall (M-K) trend test and Sen′s slope analysis were performed to obtain the trend of winter wheat production data and corresponding meteorological data from 1982 to 2018 in Ningjin County.The HP filter was used to separate winter wheat yield into climatic yield and trend yield,to screen the years with high yield variability,i.e.,three high yield years and three low yield years,and to reveal the main meteorological factors affecting yields,and then to analyze the relationship between winter wheat yield and climate change. The results showed that the average temperature (0.05 ℃·a-1),maximum temperature (0.03 ℃·a-1) and minimum temperature (0.07 ℃·a-1) in wheat season increased significantly,the average wind speed decreased significantly (-0.01 m·s-1·a-1),and the multi-year mean value of total ET0 was 600 mm with a not clear increasing trend.The multi-year average of actual winter wheat yield was 5 330kg·ha-1.Both the actual and trend yields showed a significant increasing trend with Sen′s slopes of 136 kg/(hm2·a-1) and 139 kg/(hm2·a-1),respectively.Though the climatic yield trend did not show a clear change trend,it varied from -1 245 to 1 376 kg·ha-1(-41%~26%),indicating a great variation in different years.The climate variables in big low yield and high yield seasons were analyzed and the main factors to influence wheat yield were summarized.Generally,extremely low temperature during the sowingregreening period (for example December 8 and 9,1986,the daily minimum temperature reached -21.2 ℃,and the average minimum temperature from January 14 to 25,1993 reached -14.1 ℃),un-sufficient irrigation during a jointingheading period (1993) and excessive precipitation in late planting period (2008) would lead to wheat yield reduction.The increases in sunshine hours and temperature are beneficial to wheat production. The trends of climate elements are consistent with the findings of most studies in the north China plain,indicating that climate change in the study area is consistent with the trends of climate change at larger spatial scales.Yields in the study area increased at a faster rate in the 1990′s,indicating a significant increase in the level of winter wheat cultivation during that period.The influence of climate factors on winter wheat yield in low yield years shows that extremely low temperatures during the sowingregreeningperiod,un-sufficient irrigation during the jointingheading period,and excessive precipitation in the late planting period can all lead to wheat yield reduction.The main meteorological factors causing yield reduction varied with growth seasons,indicating the complexity of climate effects on wheat yield production.The influence of climate factors on winter wheat yield in highyielding years shows that the increase in sunshine hours is more beneficial to wheat yield under the condition that the temperature remains consistent with the multi-year average.The main meteorological factors causing yield increase are similar in different years,indicating the consistency of climate factors on wheat yield increase.
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