Effects of air temperature change on spring wheat growth at different altitudes in northwest arid area

Based on the 1981-2006 observation data from agricultural meteorological stations at Minle (high altitude) and Zhangye (low altitude) in northwest arid area,the effects of air temperature change at the two altitudes on the growth and yield of spring wheat were studied. It was shown that during study period,the air temperature at the two altitudes had an increasing trend,and the increment was greater at high altitude than at low altitude. At high altitude,the growth duration of spring wheat shortened but the grain yield increased; while at low altitude,the growth duration shortened and the yield decreased. When the mean daily air temperature during spring wheat growth period increased by 1 ℃,the growth duration shortened by 8.3 days at high altitude and by 3.8 days at low altitude. The growth duration and grain yield of spring wheat at high altitude had a slight increase when the maximum air temperature during growth period was below 30.4 ℃,but decreased when the maximum air temperature was above 30.4 ℃.