Abstract:

Assessing the responses of crop growth to elevated CO₂, irrigation and nitrogen restriction in the latest version of the Community Land Model (CLM5) is crucial for the further development of its crop module. In this study, spring wheat observations from the pioneer Free-Air CO₂ Enrichment Experiment Site (FACE Experiment) located in Maricopa, Arizona, USA were used to validate the response of the CLM5 model spring wheat growth to elevated CO₂ concentration, irrigation and nitrogen fertilization, as well as the interactions among them. The results showed that: (1) after parameter calibration, the CLM5 model was able to reasonably simulate the seasonal growth of spring wheat, but there was a certain degree of bias, with an overestimation in simulating above-ground biomass by 92.0g×m⁻², and an underestimation in modeling grain yield by 39.0g×m⁻². (2) Elevated CO₂ concentration promoted spring wheat growth and yield enhancement. Under increased CO₂ conditions, the observed yield increased by an average of 14.3%, while the simulated yield showed an average increase of 22.7%, indicating a certain degree of overestimation in the model compared to actual observations. (3) Irrigation and nitrogen limitations were detrimental to the growth of spring wheat and led to a decrease in spring wheat yield, with the observed yield decreased by an average of 28.5% and 22.4%, respectively. The elevated CO₂ mitigated the yield reductions caused by moisture restriction but exacerbated those caused by nitrogen fertilizer restriction. The CLM5 model was able to capture these environmental changes effects on spring wheat yields, but with bias. Simulated spring wheat yields were decreased by 5.5% under water restriction and 44.5% under nitrogen fertilizer restriction. The CLM5 model can reasonably simulate the growth of spring wheat, and can to some extent simulate the effects of increased CO₂ concentration and water and fertilizer restriction on the growth and yield of spring wheat.

Key words:

CLM5 model, Growth and yield of spring wheat, Elevated CO₂ concentration, Water and fertilizer restriction, FACE experiment