Improving wheat developmental model based on dynamic changes in accumulated temperature demand

The dynamic response and adaptation mechanisms of crop phenology to climate change have not been extensively studied. At present, the mainstream process mechanism models have not yet considered the adaptability of crop phenology to climate. The simulation of crop development process is generally driven by temperature, especially the development rate during the reproductive growth season is assumed to be only affected by temperature. The development rate of wheat is also affected by photoperiod, temperature cycle, vernalization, and growth continuity effects. This article uses long-term and multi variety wheat phenological observation data, combined with historical climate data and field management data, to identify the dynamic changes in wheat phenology and accumulated temperature demand in China from 1981 to 2018. It reveals the mechanism of wheat dynamic response and adaptation to climate change, couples indicators reflecting phenological plasticity, and improves the models of nutritional growth period and reproductive growth period respectively. The main results and conclusions of the research are as follows: (1) The dynamic changes in wheat accumulated temperature demand, even for the same variety and stage, there are differences in accumulated temperature demand in different environments. The dynamic nature of accumulated temperature indicates that previous models based on the assumption of constant accumulated temperature are difficult to apply to changing environments. (2) The increase in temperature shortened the reproductive growth period of winter wheat, and this effect tended to intensify during the study period. The rhythmicity of day night temperature can slow down the accelerated development of nutrient growth due to warming. The wheat variety is shifting towards a weaker winter orientation, and the weakened vernalization effect leads to an increase in accumulated temperature required for phenological occurrence. For the reproductive growth period, the flowering period will affect the development rate of wheat during the reproductive growth period, and the response of temperature to maturity period is delayed. The effect of flowering temperature on phenology will continue for 8-15 days after flowering. When the flowering temperature exceeds 26 ° C, the impact on maturity period will last for more than 20 days. (3) For the flowering period of spring wheat, the model considering the effects of photoperiod and temperature cycle on accumulated temperature has the best performance, while for the flowering period of winter wheat, the model considering the effects of photoperiod and vernalization on accumulated temperature has the best performance. The nonlinear plasticity model is the optimal model for simulating the maturity period of spring and winter wheat. The use of optimized models to simulate the flowering and ripening stages of wheat reduced the average simulation error by 22.71% and 22.19% compared to traditional models.