Uncertainties in Assessing the Effects of Changing Climate and Management Factors on the Non-stationary Response of Spring-wheat Yield

Abstract:

Achieving food security goals in the face of unprecedented global warming depends on adaptation measures implemented at the local and regional scales. The non-stationary response of agricultural and hydrological systems to climate change, however, makes the design and implementation of adaptation strategies inevitably challenging. Assessing non-stationary behavior of agricultural crop yields under changing climate and understanding natural and anthropogenic factors driving such non-stationary response of soil-plant-water systems are key for sustainable management and planning of adaptation measures. In this study, we quantified impacts of management operations and climate model projections on spring-wheat yield in the Red Deer watershed in southern Alberta, Canada using the physically process-based Soil and Water Assessment Tool (SWAT). The SWAT was calibrated and validated using the best available yearly spring-wheat yield data at the agricultural region level for the baseline period of 1983 to 2007. Results were projected and analyzed for the 2040 to 2065 period. We calculated the share of the model parameters, General Circulation Models, Representative Concentration Pathways, and downscaling techniques in the cascade of uncertainties considering three nitrogen application rates to address the non-stationarity in the plant-water-soil-atmosphere system. Decomposition analysis showed a strong spatiotemporal variation of crop yield response to soil, plant, and climate variables as well as management practices. Results revealed that the high reliance of crop yield to water stress makes the largest share of uncertainty in drier regions. Overall, the outcome of this study uncovers important information of how crop yields are affected by various physical and biochemical processes and how their response is influenced when these processes are compounded by climate change.