Validation of spring wheat responses to elevated CO2 , irrigation, and nitrogen fertilization in the Community Land Model 4.5

Since then, the crop model in CLM has been evolved remarkably, but some of the key crop growth responses to environmental conditions (such as the elevated CO2) have not been well validated. Here, we set up single point simulations with CLM (version 4.5) and validated spring wheat growth response against the Maricopa spring wheat Free Air CO2 Enrichment (FACE) experiment that consisted of multiyear paired treatments to understand the growth response to elevated CO2, irrigation, nitrogen fertilization, and their interactions.

Overall, CLM showed too positive growth response to elevated CO2 but insufficient growth response to irrigation. The overestimated growth response to elevated CO2 may be due to ignoring factors (e.g., leaf traits) that will limit crop growth under elevated CO2. The insufficient response to irrigation is due to CLM simulating lower latent heat flux during April and May, which resulted in higher soil moisture.