Assessment of the impact of future climate change on maize yield and water use efficiency in agro-pastoral ecotone of Northwestern China

Maize plays an important role in the Agro-pastoral ecotone of Northwestern China (APENC), where highly sensitive to changes in climate conditions. However, little is reported on the impacts of climate change on crops in the region. In this study, we used Decision Support System for Agrotechnology Transfer model driven by future climate data from 20 general circulations models under two representative concentration pathways (RCPs: RCP4.5 and RCP8.5) from the Coupled Model Intercomparison Project Phase 5 (CMIP5) to project the effects of climate change on maize yield and water use efficiency (WUE) in eight future time periods (interval: 10 years; from 2020s to 2100s). The model was first calibrated based on field observation for phenology, leaf area index, maize yield and calibrated and evaluated results were reasonably good. Simulated results showed that without and with consideration of CO2 effects, maize yield at the end of the 21st century will decrease by 11.7% and 10.3% under the RCP4.5 scenario, and by 22.1% and 21.2% under the RCP8.5 scenario, respectively. We found that there is a significant correlation between maize yield reduction and warming. Specifically, when the increment of annual average temperature reaches 1 degrees C, the maize yield begins to decrease by 11.27% and 10.8% per 1 degrees C warming without and with consideration of CO2 effects, respectively. Furthermore, high temperature not only affects maize yield but also has a negative effect on WUE. The WUE would change by -8.1% and -18.8% under RCP4.5 and RCP8.5, respectively. But if we consider the effects of CO2, the WUE will improve 1.5% under RCP4.5 and 2.2% under RCP8.5, in comparison to those without consideration of CO2 effects. Overall, future climate warming will seriously affect maize yield and WUE. Although the increase of CO2 concentration is beneficial to raise maize yield and WUE, it is hard to offset the negative effects of the increase in temperature. Besides, change in the planting date can be beneficial for the adaptation of maize to climate change in the APENC. These results will provide comprehensive information to support local policy and decision-making in agricultural production and water resources management.