Influence of global warming on winter wheat yield in Henan Province

Agriculture is one of the industries that is most sensitive to global warming. Crop yield analysis is an efficient approach to evaluating the impact of climate change on agriculture. Henan Province (which is in the south region of North China Plain) is one of the most important production bases of winter wheat, a crop that is sensitive to global warming. This study used historical climate data and average winter wheat yield to determine the trends in precipitation and temperature during winter wheat growing season in Henan Province. It then utilized the extracted climatic productivity and Mann-Kendall mutation testing method to separate two distinct stages of the effects of climate change on agriculture. For each of the stages, regression equations were also established among temperature, climate change and yield. Then the impact of warming climate on unit yield of winter wheat was eventually analyzed at each stage using the equations. While there was no drastic change in precipitation during the 1961~2007 winter wheat season in Henan Province, the temperature rose continuously. In comparison with precipitation, temperature showed significant correlations with climate and unit yield of winter wheat. For the period of 1961~1981, the correlation between winter wheat yield and temperature departure was significant and positive. This correlation weakened after 1987, after which time yield fluctuation was limited. Since the mid 1980s, air temperatures during winter wheat seasons in Henan Province increased dramatically, with an average temperature increase of 0.81 oC per decade. In comparison with 1961~1981 (the pre-warming stage/period), wheat yield increased by 173.4%~245.9% in 1991~2000 and 2001~2007, and the contribution rate of temperature rise was 15.6%~20.7%. Average temperatures were relative higher in wintering, re-greening, heading and flowering stages. Warming positively influenced unit yield of winter wheat, as average temperatures were lower than the suitable temperature range. In the conspicuous 2001~2007 warming period, however, only 1.0% of the yield increase was due to temperature rise. This showed that unit yield of winter wheat increased with improved cultivation techniques. The study showed that while the sensitivity of yield to temperature variation decreased, the adaptability of agriculture to environment factors increased.