A quantitative method for determining the impact threshold of climate change for agriculture

As the global climate changes, different degrees of variation in climatic factors will have various impacts on agricultural production, leading to appropriate or stressed conditions. The impact threshold of climate change (ITCC) for agriculture refers to the value of a climatic factor at which the agricultural status mutates. Due to the urgency of addressing the negative impacts of climate change on agriculture, research on the ITCC of agriculture is crucial. Here, we built models to reflect the relationship between agricultural climate yield and climatic factors based on climate change characteristics and objective agricultural status. Using the models, we obtained the appropriate and stressed thresholds of different climatic factors. We calculated the ITCC of spring wheat in Wuchuan County as an example and identified warming and drying trends in Wuchuan County from 1961 to 2013, especially during the period from 1991 to 2013 (i.e., the period after mutation or the change period). Over the past 53 years, spring wheat yield increased with an average rate of 81.3 kg ha−1 dec−1. Over the change period, however, yield decreased with an average rate of 13.8 kg ha−1 dec−1 and the fluctuation range increased. The appropriate threshold for average temperature during the growth period of spring wheat was 11.4 °C, and the stressed thresholds were 8.2 and 14.6 °C. The appropriate threshold for precipitation during the growth period was 391.1 mm, and the stressed thresholds were 247.4 and 534.9 mm. During the period before mutation (i.e., the basic period), the average temperature was below the upper temperature threshold, and precipitation was 26.9 mm above the lower precipitation threshold. During the change period, the average temperature was 0.3 °C above the upper temperature threshold, and precipitation was 9.8 mm above the lower precipitation threshold.