Effect of temperature increase on dryland spring wheat yield in different precipitation years

Climate change significantly affects crop production. To explore the effects of temperature increase on dryland spring wheat yield in different precipitation years in the hilly regions of the Loess Plateau, this study incorporated the meteorological data of Dingxi City, Gansu Province, from 1979 to 2018. Dryland spring wheat yield was simulated with the Agricultural Production Systems Simulator (APSIM) model when the daily maximum and minimum temperatures changed in the range of 0-2℃ in different precipitation years. Quadratic polynomial regression, single-factor analysis, and path analysis were used to study the influence mechanisms of temperature increase on dryland spring wheat yield. The results showed that the relationships between dryland spring wheat yield and daily minimum temperature, and between dryland spring wheat yield and daily maximum temperature were quadratic parabolas with an upward opening in different precipitation years, without a threshold value. When the daily maximum temperature was constant, an increase in the daily minimum temperature had a positive effect on the yield. The effect of increasing production was as follows: drought year > normal year > wet year. For every 0.5℃ increase in the daily minimum temperature, the average dryland spring wheat yield increased by 1.32% in wet years, 3.06% in normal years, and 3.99% in drought years. When the daily minimum temperature was constant, an increase in the daily maximum temperature had a negative effect on yield. The effect of production reduction was as follows: drought year > wet year > normal year. For every 0.5℃ increase in the daily maximum temperature, the average dryland spring wheat yield decreased by 9.08% in wet years, 7.98% in normal years, and 9.18% in drought years. The yield thresholds reached 798.61 kg·hm^-2 in wet years when the daily maximum temperature increased by 7.1℃, 1118.21 kg·hm^-2 in normal years when the daily maximum temperature increased by 3.9℃, and 1026.88 kg·hm^-2 in drought years when the daily maximum temperature increased by 3.1℃. Increased temperature led to a decrease in dryland spring wheat yield in different precipitation years. There was a negative interaction between the daily maximum temperature and daily minimum temperature. The effect of reduced production caused by increased daily maximum temperature was much greater than the effect of increased production caused by increased daily minimum temperature.