# Modeling the Impact of Atmospheric Warming on Staple Crop Growth in China in the 1960s and 2000s
## 3 Results
### Temperature Change Effects on Crop Productivity in Key Growth Periods  
A comparison of the key growth periods before and after heading (silking) (Table 4) showed that relative to the 1960s, the daily mean temperatures in the vegetative growth stage before heading (silking) and in the reproductive growth stage after heading (silking) almost always increased in the 2000s, except for the maize in Fengqiu during the vegetative growth period (from 27.6 \({}^{\circ}\)C in the 1960s to 27.1 \({}^{\circ}\)C in the 2000s), but the distribution  
Figure 3: Simulated crop gross primary productivity (GPP), respiration (RA) and above ground biomass (AGB) (g C m\({}^{-2}\)) for the 1960s and 2000s: (**a**) rice, Changshu, Jiangsu province; (**b**) single rice, Sanjiang, Heilongjiang province; (**c**) early rice, Taoyuan, Hunan province; (**d**) late rice, Taoyuan, Hunan province; (**e**) winter wheat, Changshu, Jiangsu province; (**f**) winter wheat, Fengqiu, Henan province; (**g**) summer maize, Fengqiu, Henan province; (**h**) spring maize, Halilun, Heilongjiang province. Red, blue and green lines, respectively, represent simulated GPP, RA and AGB values for the two periods, and dashed lines pertain to the 1960s, while solid lines pertain to the 2000s. of optimum temperature days was different. Compared to the 1960s, the number of optimum temperature days increased 30 days before heading for Early rice in Taoyuan which was offset by the 15 days decrease in optimum temperature days after heading in the 2000s. Similarly, for Late rice in Taoyuan, compared to the 1960s, the number of optimum temperature days decreased 42 days before heading, which was offset by the 45 day increase in optimum temperature days after heading in the 2000s. All of the above resulted in few changes in the AGB of rice in South China (Table 4). However, the increase in optimum temperature days before and after heading for rice in Sanjiang made virtually the equal contribution to the increase in AGB in the two growth periods. The observed increase in AGB for winter wheat in North and East China was mainly attributable to a significant increase in the number of days with optimum temperatures before heading. In the 1960s, there were 124 optimum temperature days before heading in North China, and this number increased to 190 days in the 2000s. For winter wheat in East China, there were 90 optimum temperature days before heading in the 1960s, and this number increased to 162 days in the 2000s. However, no significant differences in the number of optimum temperature days were found between the two periods after heading. Relative to the 1960s, summer maize in Fengqiu in North China in the 2000s experienced a minor change in temperatures before and after silking, and thus the AGB of maize in this region remained basically unchanged. For spring maize in Hailun in Northeast China, compared to the 1960s, the average temperature increased by 1.3 \({}^{\circ}\)C before and after silking in the 2000s. The number of optimum temperature days before and after silking increased by 61 and 57 days, respectively, leading to an increase in AGB both before and after silking. In general, warming before heading (silking) made more significant contributions to increases in AGB.