Evaluating the effect of climate change on crop yield in the St. Joseph River Watershed, Eastern Corn Belt

Abstract

Abstract. CO2 concentration is predicted to increase in future. Usually, crop production responds positively to the enhanced CO2 level due to increased carbon assimilation and decreased stomatal conductance, which improves the plant-water relation. Plant drought tolerance is supposed to be improved due to the reduced transpiration and higher soil water content. Elevated CO2 level is deemed to mitigate the negative effects of climate change in this area because of increased spring wetness and decreased summer rainfall. Therefore, cooperating CO2 level enhancement in crop yield simulation is critical to accurately evaluate climate change impacts. How does increased temperature, decreased summer moisture combined with CO2 level enhancement affect crop yield will be seriously assessed over the St. Joseph River Watershed in Eastern Corn Belt, USA using an existing ecohydrology model (SWAT 2012). A multi-objective calibration strategy is first applied in historical period (1991-2010) to constrain simultaneous prediction of interannual crop yield, seasonal crop growth and surface water budget under current CO2 concentration level. Then Coupled Model Intercomparison Project Phase 5 (CMIP5) data from three Global Circulation Models (CCSM4, GFDL-esm2m, MICROC5), under three Green House Gas Emission Scenarios (RCP 2.6, RCP 4.5, RCP 6.0) at two future periods (Near future: 2031-2050; Far future: 2071-2090) are utilized as climate input for calibrated model. CO2 levels for different Green House Gas Emission Scenarios at two future periods are also considered for model simulation. Soil moisture, physiological stresses and crop yield predictions for two future periods are compared with the historical period to quantify future climate change impacts on crop production in the study area