Impact simulation of climate change on potential and rainfed yields of winter wheat in Southwest China from 1961 to 2010

Using crop and soil data from agro-meteorological observational stations together with meteorological data from meteorological stations, the study evaluated the adaptability of APSIM-Wheat (Agricultural Production Systems sIMulator- Wheat) model in winter wheat planting zones in Southwest China (SWC). Then, the model was used to calculate the potential and rainfed yields of winter wheat from 1961 to 2010 in SWC. The relative contribution rates of the changes in main climatic factors during crop growing season to the changes in simulated potential and rainfed yields of winter wheat were determined with the stepwise regression method. The study results showed that APSIM-Wheat model performed well in simulating phenology, above-ground biomass and yield of five representative winter wheat varieties in SWC. Root Mean Square Error (RMSE) between simulated and observed wheat phenology were less than 7.0 d for all the varieties. Normalized Root Mean Square Error (NRMSE) between simulated and observed above-ground biomass and yield were lower than 25% and 21%, respectively, for all the varieties. Total solar radiation during wheat growing season decreased significantly at 36% of the study stations centered in the northern, southeastern and mid-southern SWC. The effective accumulative temperature of not less than 0 ℃ during wheat growing season increased significantly at 68% of the study stations centered in the western SWC, while average diurnal temperature range during wheat growing season decreased significantly at 30% of study stations centered in the mid-southern SWC (P < 0.05). Total precipitation during wheat growing season decreased at most of study stations centered in the southern and southeastern SWC from 1961 to 2010. As a result, simulated potential yield of winter wheat also showed a significant decline at 65% of study stations, especially in the mid-southern and northern SWC. Simulated yield of rainfed wheat showed a significant decline at 25% of study stations, especially in the northern SWC. The contribution rates of the decrease of solar radiation and diurnal temperature range, the increase of temperature during wheat growing season were 45%, 2% and 36%, respectively, to the reduction in simulated potential yield, and 36%, 39% and 8%, respectively, to the reduction in simulated yield of rainfed wheat. The contribution rate of decreasing precipitation during wheat growing season was 7% to the reduction in simulated yield of rainfed wheat. In general, solar radiation and temperature had the most obvious effects on simulated yield variations of winter wheat in SWC from 1961 to 2010. The decrease in solar radiation and precipitation, and the increase in temperature during winter wheat growing season led to a decline in both simulated potential and rainfed yields at most of study stations in SWC, while the decreased diurnal temperature range had both negative and positive effects on potential and rainfed yields, respectively. Quantifying the impacts of light, temperature and precipitation on wheat production using APSIM model provided a sound foundation for taking countermeasures for adapting to climate change and improving wheat yield in Southwest China.